Vegetable Transplant Production

Vegetable transplants are commonly grown in New England in greenhouses for field transplanting or spring sales at farm market stands. Many vegetable crops are grown from transplants in New England due to the late spring, short growing season and desire to obtain mature, harvestable crops as soon as possible.

Transplant production is a specialized part of vegetable production that requires a protected environment such as a greenhouse and careful attention to detail. Although vegetable transplants may only be in the greenhouse for a short period of time, it is important to produce high quality pest-free transplants. Scheduling, plant nutrition, greenhouse management, and pest management influence quality. Some vegetable producers choose to purchase transplants while others grow their own.

Cleaning and Disinfecting the Greenhouse 

The protected greenouse environment needs to be  regularly cleaned and disinfected to reduce potential for diseases such as damping off, crown and root rots.  Weeds need to be removed to reduce the potential overwintering sites for many different insect pests.   While the greenhouses are empty, between crop cycles, is an ideal time to clean and disinfect your greenhouses.  Remove all weeds, plant debris, spilled potting media and organic debris. Thoroughly sweep,  and then scrub or power wash to remove all organic crop debris off greenhouse floors, benches and walls. Follow this with a high-pressure water cleaning. 

Many growers use specific greenhouse cleaners, such as Strip It Pro, which is a blend of acids, surfactants and wetting agents that can be applied with a foaming attachment, removing organic matter and mineral deposits without scrubbing.  Apply with a foamer and allow to sit for 5 minutes before rinsing with a high-powered hose. 

After the surfaces are thoroughly cleaned, you can then use a disinfectant. There are many commerically available disinfectants developed for greenhouse use.  Each product has a specific range of activity on different types of surfaces (wooden benches are more difficult to clean than wire mesh benches). Follow all label safety precautions including recommended rates, use of personal protective equipment (PPE), and plant safety precautions.  Some of the products commercially available include Q Salts such as GreenShield 11, and KleenGrow; hydrogen peroxide products such as ZeroTol 2.0OG, Jet-AgOG,  SanidateOG and PERPose PlusOG.  All are strong oxidizing agents. 

Use chlorine bleach with caution, as it is highly volatile, and can irritate skin and eyes.  It should only be used in a well-ventilated area. Mix fresh solutions just before use. It's half life, (the time required for a 50% reduction in strength of a chlorine solution) is only two hours.   Chlorine is also corrosive.  Repeated use may be harmful to plastics or metals.   Chlorine bleach is also phytotoxic to some plants.  Walks, benches, and plant containers can be treated in nurseries. 

Containers to be re-used should be washed thoroughly to remove media particles and plant debris before being treated with a disinfectant.  The smaller the container, the harder it is to effectively remove debris. Smaller plug trays are much more difficult to clean than larger containers. Plant trays should also be  thoroughly cleaned and disinfected. 

Alcohol (70%) can be used to sanitize knives or cutting tools. 

Clean and disinfect irrigation systems. 

Avoid using Unvented Heaters in Greenhouses 

One of the most critical features in greenhouses is a source of heat to provide appropriate temperatures. A frequent question by growers is regarding the use of supplemental heaters in the early spring.  Do not use unvented heaters when growing transplants in the greenhouse or high tunnel. An unvented heater is one that is designed without a flue connection so that the heat and products of combustion are exhausted into the greenhouse. Unvented heaters can be fired with natural gas, propane or kerosene which all contain traces of sulfur.  During combustion sulfur in the fuel is combined with oxygen to form sulfur dioxide. Levels as low as 0.5 parts per million (ppm) can cause injury to some plants. Once the sulfur dioxide enters the plant through the stomates, it reacts with water to produce sulfuric acid that causes leaf burn, flecking and general chlorosis. Tomatoes and white petunias are very sensitive and will show damage in as little as one hour. 

Ethylene gas is another pollutant formed during combustion. Ethylene levels as low as 0.01 ppm can cause damage, including malformed leaves, epinasty (downward bending of leaves) and flower senescence.  Tomatoes are a good indicator plant for ethylene because they develop downward bending of the leaves when exposed. Some growers place tomato plants in each greenhouse when they begin heating in the winter.  Problems are more common when the outdoor temperatues are cold so there is more demand for heat and double poly greenhouses or hoophouses are tightly sealed.  

Greenhouse Management Transplant Production Resources

Aldrich, R. and Bartok, J. Greenhouse Engineering, https://ecommons.cornell.edu/bitstream/handle/1813/69429/NRAES-033.pdf?sequence=1

Bartok, J. Greenhouses for Homeowners and Gardeners: PALS Publishing (Formerly NRAES), https://ecommons.cornell.edu/handle/1813/69450

Most recent version, New England Greenhouse Floriculture Guide: A Management Guide for Insects, Diseases, Weeds and Growth Regulators, available from: https://greenhouseguide.cahnr.uconn.edu/

University of Massachusetts Extension Greenhouse Crops and Floriculture Program: https://ag.umass.edu/greenhouse-floriculture

University of Conn Extension Greenhouse IPM Program: https://ipm.cahnr.uconn.edu/greenhouse/

Types and Varieties

For Field Production: Consult with your seed supplier and review the individual crop sections in the manual for suggested varieties that grow well in New England. Grow the crops at appropriate temperatures. Pay particular attention to scheduling times, light, temperature and nutritional requirements needed to grow healthy transplants.

With the exception of a few perennial vegetables, vegetable plants are started from seed. Brussels sprouts, broccoli, cabbage, lettuce and tomatoes are easy to transplant vegetables that are able to absorb water efficiently and form new roots rapidly. Vegetable plants that are a little more difficult to transplant do not absorb water as efficiently, but form new roots quickly include celery, eggplant, onion and pepper. Vegetable plants that are difficult to transplant include cucumbers, melons, summer squash and sweet corn.

For Spring Bedding Plant Sales: There are so many choices, from gourmet greens and vegetable amaranth (popular in Southern Asia, Africa, and West Indies) to yellow cherry tomatoes and an assortment of colored peppers and eggplants. To find new varieties to grow for spring bedding plant sales, see the All American Selection (AAS) Winners website www.all-americaselections.org/, the National Garden Bureau website https://ngb.org/ and your favorite seed supply company catalogues. State university trial results can also help you select varieties that will perform best in your area.

Growing Media and Nutrition

There are numerous factors affecting the growth of vegetable transplants including types of growing media, watering practices and fertilization programs.

Types of Growing Media

Growing media for vegetable transplants in greenhouses contain a variety of soilless ingredients such as peat moss, vermiculite, perlite, shredded coconut husks (coir), or composted materials plus starter nutrients and a wetting agent. Field soils are generally unsatisfactory for the production of plants in containers because soils do not provide the aeration, drainage and water holding capacity that are required. They also need to be pasteurized or fumigated to prevent the development of diseases and germination of weed seeds.

Premixed media is common in the greenhouse industry. Suppliers offer a diversity of mixes that are available prepacked (in bags, bales, super sacks) or in bulk. Growing media is designed to achieve high porosity and water retention while providing adequate aeration.  Recipes are specially formulated for propagation, specific crops or general use. Soilless media purchased in bags do not have to be pasteurized or fumigated before use. Preventative applications of biological fungicides or fungicides may be necessary with vegetable transplants prone to damping off. Growers can also obtain commercially available mixes with biological fungicides added to the mix. Those containing mycorrhizae, though increasingly common, may have been prepared many months in advance and may contain insignificant concentrations of living inoculum. 

Compost-based mixes are also available commercially as a substitute for traditional soilless media, especially for organic production. See section below on organic vegetable transplant fertility.

Media Testing

Test your growing medium to adjust your fertilizer program and to manage the pH to prevent nutritional problems.  Samples from soilless mixes are tested differently than samples from field soil. Unlike field soil tests that extract nutrients with weak acid solutions, soilless media  and organic media with compost are mixed with distilled water at a standard dilution and then analyzed. There are three commonly used methods of testing soilless media using water as an extracting solution: saturated media extract (SME), 1:2 dilution method, and leachate Pour Thru.  Most soil testing laboratories use the SME method. The values that represent each method of testing are different from each other. Likewise, values for specific nutrients are likely to differ with testing methods.  Always use the interpretative data for the specific soil testing method used to avoid incorrect interpretation of the results. Most soil testing laboratories use the SME method. The 1:2 and Pour Thru are methods that can be used by growers on-site using portable soil testing meters. Since different soil testing laboratories may use different dilutions, it is not advisable to compare soil test results from one laboratory to those obtained from another. Use one laboratory for consistent results. It is helpful to let the laboratories know you are submitting greenhouse samples ahead of time. 

In addition to carrying out a complete soil test, growers should routinely check the electrical conductivity (EC) or soluble salts and pH of their growing media.  These tests can be done on-site using portable testing meters, or samples can be sent to a university soil testing laboratory.

Taking a Sample: Take several samples at root depth from several containers and mix together in a clean container. Sampling several containers is important because a sample from one pot or flat could be an anomaly (values too high or too low) misrepresenting the crop as a whole. Sample about 2 hours after fertilizing or at least on the same day. If slow-release fertilizer pellets are present, carefully pick them out of the sample. If the pellets are left in, they can break during testing and this may result in an overestimation of fertility.

Be consistent in sampling procedures each time you sample. A lot of variability can be introduced to tests due to inconsistent sampling and this diminishes the value of testing especially if when you are monitoring fertility levels overtime.

Take about one  to two cups of the medium and dry at room temperature. Place in a sandwich size zip-type bag and close it tightly. Label each sample on the outside of the bag with the sample bag or number.  Be consistent in sampling procedures each time your sample. 

pH: The term pH refers to a measurement of the hydrogen ion concentration (how acidic or basic a solution is).  The pH can range from 0 (very acidic) to 14 (very basic). Growing medium pH drives the chemical reactions that determine whether nutrients are either available for root uptake (soluble) or unavailable for root uptake (insoluble).  Major influences on the media pH include limestone in the growing media, irrigation water pH and alkalinity, and the acid/basic nature of fertilizer solution used. Smaller cells and plugs are subject to very rapid media pH change.

The optimum pH range for vegetable bedding plants grown in soilless media is 5.5-6.5.

Electrical Conductivity (EC) or Soluble Salts: Soluble salts are the total dissolved salts in the root substrate (medium) and are measured by electrical conductivity (EC). Most fertilizers (except urea) are salts and when placed in solution they conduct electricity. Measuring EC or soluble salts provides a general indication of nutrient deficiency or excess.  A high EC reading generally results from too much fertilizer in relation to the plant’s needs, but inadequate watering and leaching or poor drainage may be other causes.  Sometimes, high EC levels occur when root function is impaired by disease or physical damage. Always check the condition of the root system when sampling growing media for testing.

Water Quality and Alkalinity: The quality of water used for irrigation and mixing fertilizers should be tested each year for pH, alkalinity and electrical conductivity.  A standard greenhouse water test includes pH, EC, alkalinity as well as macro and micronutrients (N, P, K, Ca, Mg, S,B, Cl, Cu, Fe, Mn, Mo and Zn) and sodium (Na).  Testing should be done at least once per year.  (This is a different test from the water test that is done for microbial quality).  Water containing a large concentration of dissolved salts can cause high soluble salts damage.

Water alkalinity is a measure of the water's capacity to neutralize acids. An alkalinity test measures the level of bicarbonates, carbonates and hydroxides in water. Test results are generally expressed as ppm of calcium carbonate. Irrigation water tests should always include both pH and alkalinity. A pH test itself is not an indication of alkalinity. Water with high alkalinity (i.e., high levels of bicarbonates or carbonates) always has a pH value of 7 or above, but water with high pH does not always have high alkalinity. This is important because high alkalinity exerts the most significant effects on growing medium fertility and plant nutrition.

Water with high alkalinity (>150ppm CaCO3 of alkalinity) can result in iron deficiency chlorosis caused by increased root medium pH over time. This is usually influenced by the water source. Water with low alkalinity will have little ability to neutralize acidity. It is advisable to have your water tested prior to the spring growing season. High alkalinity can be reduced by injecting acid into the irrigation water. While most greenhouses use sulfuric acid, citric acid is approved for certified organic production. Calculate the amount of acidification required using the UMass Greenhouse Crops and Floriculture Program page: https://ag.umass.edu/greenhouse-floriculture/fact-sheets/adjusting-alkalinity-with-acids.

Fertilizers and Media pH

Most water-soluble fertilizers will change the potting media pH to some extent. Ammonium and urea-containing fertilizers lower media pH; nitrate fertilizers raise it.  Potential acidity or basicity is printed on the fertilizer label based on pounds of calcium carbonate per ton of fertilizer.  For example, if a 20-10-20 has a potential acidity of 429 pounds per ton, then the reaction produced by one ton of fertilizer will neutralize 429 pounds of calcium carbonate. If 15-0-15 has a potential basicity of 420 pounds per ton, then the reaction produced by one ton of the fertilizer will be equivalent to 420 pounds of calcium carbonate.  Changes in pH of the media are caused by plant responses to the forms of nitrogen. Because fertilizers can be used to manipulate the pH of the growing media, most growers alternate fertilizers to balance the pH of the growing medium.

Fertilizer Injectors: In conventional greenhouses, nutrients are delivered using various water-soluble fertilizers through a fertilizer injector, through the use of controlled-release fertilizers, or using a combination of these two methods.

Fertilizer injectors are used in liquid feeding systems. These devices inject a small quantity of concentrated fertilizer solution (stock solution) into the irrigation line so that the water leaving the hose (dilute solution) supplies the proper concentration of fertilizer. When applied at every watering, this is known as “constant feed.” Rates of fertilization are often given in parts per million (ppm) of nitrogen, which is a way of expressing the fertilizer concentration. The amount of fertilizer to dissolve per gallon of water (stock solution) to make the appropriate concentrate for a specific injector setting needs to be determined. This information is listed on the bag of fertilizer. An injector setting of 1:100 indicates that 1 gallon of fertilizer concentrate delivers 100 gallons of final solution. It  is not an indication that the injector is delivering 100 ppm of fertilizer solution.

Choosing Fertilizers: Factors to consider when choosing fertilizers include the ratio of ammonium to nitrate-N, trace element starter charge, content of calcium and magnesium, and potential acidity or basicity. There are many fertilizers available to use for vegetable bedding plant production. Commonly used fertilizers include 15-0-15 (Dark Weather Feed), 15-16-17 and 20-10-20,  15-5-15 ("Cal-Mag"), and 13-2-13.

Plug Production (15-5-15, 13-2-13) Both fertilizers combine high nitrate, low phosphate with extra calcium and magnesium, plus micronutrients. 15-5-15 is a little less basic (raises pH) than 13-2-13 and contains less nitrate and a little more phosphorus. Both are commonly used for plug production.

Peat-Lite Specials (15-16-17, 20-10-20, 21-5-20). These fertilizers are among the most popular for routine fertilization of vegetable bedding plants. All are high (>50%) nitrate fertilizers. However, these fertilizers also have elevated trace element levels which may raise iron (Fe) and manganese (Mn) to toxic levels at low pH. All are acid-forming fertilizers, but 20-10-20 has the greater potential acidity.

General Purpose (17-5-17, 17-3-17, 17-4-17). All are high (>50%) nitrate fertilizers with calcium, magnesium and other minor elements. All produce a nearly neutral reaction.

General Purpose (20-20-20). Growers who use this fertilizer with soilless media risk ammonium toxicity because the nitrogen in this fertilizer is 75% ammonium and urea. Some growers who use media containing soil do not appear to have problems. If 20-20-20 is used, the soilless growing medium should be tested frequently for ammonium. 20-20-20 supplies trace elements and has the greatest potential acidity of fertilizers commonly used in New England greenhouses. Tomato, eggplant and pepper plants are especially sensitive to ammonium, reducing plant growth and causing yellowing of the foliage.

Low Phosphorus (P) Fertilizers (20-0-20, 20-1-20, 15-0-15). These fertilizers can be tried as an alternative to chemical growth regulators for vegetable transplants. This technique of growth control is sometimes called "phosphorus starvation." It is generally believed that more P than necessary is being applied to greenhouse crops. Too much P may cause plants to stretch and P is a ground water pollutant. Unfortunately, in terms of height control, these fertilizers may be of no benefit if they are applied to a growth medium containing superphosphate or a high starter charge of P. Also, there is a risk of P deficiency if the fertilizers are used continuously with low P growth media. The low P fertilizers are quite different in many ways. 15-0-15 and 20-0-20 supply Calcium (Ca). 15-0-15 is a basic (raises pH) fertilizer containing about 95% nitrate and 20-0-20 is a neutral fertilizer and is 50% nitrate. 20-1-20 is an acidic fertilizer and it does not supply Ca, but it is about 70% nitrate.

Calcium Nitrate and Potassium Nitrate (15-0-15). High nitrate, high calcium fertilizer. Some growers alternate its use with the Peat-Lite Specials on a 2-3 week basis to supply Ca and to counter the acidic effect of the Peat-Lite fertilizers. If water-soluble NPK fertilizer is not applied at least once every 10-14 days, superphosphate must be incorporated into the growing medium.

Guidelines for Rates and Frequency of Fertilizer

Small, slow-growing plants should receive lower rates or less frequent application until they are well-established. Care should be taken not to over-fertilize vegetable transplants to avoid overgrown plants. Young seedlings are especially vulnerable to injury from high soluble salts.

While plants are in the plug or seedling stage, use a complete water-soluble fertilizer at 50-100 ppm N every time plants are watered and use clear water (no fertilizer) every third watering. Use the lower rate (50 ppm) early and the higher rate (100 ppm) later if the seedlings are to be held in the flat or tray three or more weeks before transplanting. Shortly after transplanting, as plants approach rapid growth, increase the rate to 200 ppm N at every watering or 300 ppm N once every 7 days, watering with clear water 2-3 times between each fertilization.

Fertilizer Solution Volume: The volume of fertilizer solution applied has a dramatic effect on the growth of the vegetable transplants. As the volume of water-soluble fertilizer increases, the quantity of nutrients delivered to the plant also increases resulting in an increase in height, stem diameter and plant weight. Doubling the volume applied also doubles the amount of each nutrient potentially available to the plant.

Plant Growth Rate and Environmental Conditions. In general, nutrient requirements of vegetable transplants are greatest during periods of rapid growth. Too much fertilizer during slow growth periods may lead to high soluble salts; failure to provide enough fertilizer during periods of rapid growth will lead to nutrient deficiency.

Nutritional Problems

Early in production serious nutritional problems include high soluble salts, trace element toxicities, and ammonium toxicity. Later in production, particularly in cell packs, plants may develop nitrogen deficiency symptoms as the earliest indication of insufficient fertility levels.

Soluble Salts. Injury to vegetable transplants from excess salts seems to be most common shortly after transplanting. The major sources of high salts are excessive fertilizer from liquid feeds or media from sources that contain high concentrations of salts.   Excessive liquid fertilizer can be applied if your fertilizer injector is not calibrated or working properly.  High salts can also come from compost based growing media.  The quality of the compost depends upon what it was made from and well well it was finished (how long it was allowed to mature).   Seedlings are much less tolerant to excess salts than established, rapidly growing plants. Some soilless mixes may contain enough "starter charge" to cause excess salts problems in the first few weeks after transplanting, particularly when a water-soluble fertilizer is also applied. Excessive drying, poor drainage, and uneven watering are factors that can aggravate this problem. Check roots of plants often and conduct regular soil tests to identify and prevent problems. It is difficult to diagnose a soluble salts problem by symptoms alone. Often nutrient deficiencies and root diseases cause the same symptoms, along with inadequate watering. A soil media test is advisable if you suspect salt injury.

Trace Element Toxicities. Iron (Fe) and/or manganese (Mn) can be accumulated to toxic levels by tomato plants. Symptoms appear as numerous small dark spots and mottling of the foliage. The potential sources of excess Fe and Mn are: trace element fertilizers in the mix, water-soluble fertilizers with elevated trace elements levels, and sometimes irrigation water. Low growth medium pH aggravates the problem by increasing Fe and Mn availability. Toxicity can be avoided by keeping the pH in the range of 5.8-6.0 for susceptible crops and by the use of fertilizers with lower trace element levels.

Ammonium Toxicity.  During cool growing conditions, (less than 60F), wet growing media and low pH, nitrifying bacteria are suppressed so that ammonium may build up to toxic levels.  Tomato, eggplant, and pepper transplants are particularly sensitive to high levels of ammonium, but other vegetable transplants can also be damaged. Symptoms of ammonium toxicity include yellowing or chlorosis between the veins, and scattered necrotic spots.  Plants may be stunted. At first, young leaves are affected, but later, older leaves show symptoms. Root tips are also damaged. 

Nitrogen and Phosphorus in Transplant Production. Nitrogen concentration in the greenhouse fertilizer program has a greater effect on the growth of transplants than either phosphorus or potassium. Raising the level of nitrogen results in taller transplants with thicker stem diameters and heavier plant weights, but applying too much nitrogen may result in soft, poor quality transplants. These lush transplants may also be more prone to phloem feeding insects such as aphids, whiteflies and to foliar blights. Phosphorus has a limited effect on the growth of transplants when compared to nitrogen, but should be included as part of a complete fertilizer. Increasing the phosphorus concentration results in a moderate increase in transplant height, stem diameter, and shoot fresh and dry weight. If phosphorus is restricted to the point at which the plants show extreme phosphorus deficiency (purple leaves and stems, stunted plants), field performance will be reduced.

Organic Vegetable Transplant Production

Growing Media and Nutrition

Types of growing media 

Conventional growing media containing synthetic ingredients (wetting agent, starter chemical fertilizer) cannot be used in organic production of vegetable transplants. However, acceptable growing media can be created from a wide variety of approved materials. These blends for organic production may be purchased off-the-shelf, custom-blended by manufacturers, or produced on-the-farm.

Purchasing a commercially prepared mix for organic production is the easiest way to get started and most growers choose this option to ensure consistency and reduce the risk of soil-borne diseases. Common components such as peat moss, perlite, vermiculite, and coconut coir are acceptable for organic certification.  Commercial mixes for organic production may contain a "starter charge" of organic fertilizer or no starter fertilizer at all.  Check with your organic certifier to make sure your mix complies with standards.  More information on growing media for organic production can be found in the ATTRA publication, " Potting Mixes for Certifed Organic Production". 

Use of Compost based growing mixes 

Compost is a renewable resource that can be made from locally sources materials or purchased locally that may be the preferred source for many organic growers to use as a growing mix.  Other advantages of adding compost to growing mixes is that it has good cation exchange properties, can function as a wetting agent in peat-based mixes, and its microbial activity may help suppress diseases. However, poorly made unfinished compost can be high in soluble salts, contain weed seeds, may emit ammonia, and may be a source of pathogens such as Pythium, Phytophthora, and Rhizoctonia.

There are many challenges to using compost in growing mixes because its chemical and physical properaties vary from batch to batch. Because each batch of compost is different, it is critical to test the media before use. (See previous section on media testing). In addition to sending samples to a laboratory for testing, you can also do in house bio-assays, seeding some quick growing oats, onions, beans or radish seedlings.  Plant these quick growing seeds several weeks before you plan on using the mix, to see how they grow and perform. You can also plant these seeds in a soilless mix to see how these seedlings compare to seedlings grown in compost. 

Before purchasing a compost-based mix, ask your vendor for more specific information on its characteristics. Composts with the US Compost Seal of Approval must meet specific standards. For use in organic production, composts must meet organic standards and be OMRI approved. Compost is rarely used by itself as a potting medium. Mixes may contain from 30 to 50% compost by volume. In research at the University of Rhode Island, mixes with 36% compost combined with peat, perlite, and vermiculate yielded a mix with desirable bulk density. 

Nutritional Problems  Some potenial nutrient issues with compost-based mixes include high excess salts, high ammonium levels, high levels of sodium, and low nutrient levels such as potassium.  The quality of the compost depends upon what it was made from and how well it was 'finished" ( how long it was allowed to mature). Finished composts may contain 5.0 mS/cm soluble salts or more depending upon the feedstocks used. However, most vegetable seedlings only tolerate a soluble salt level of 1.0 mS/cm. 

When using compost-based growing mixes, the aerobic bacteria that are needed to convert ammonium nitrogen to nitrate nirogen are dependent upon environmental conditions.  The speed of this reaction depends upon both the temperature and microbial activity. During cool growing conditions, (less than 60ºF), wet growing media and low pH, nitrifying bacteria are suppressed so ammonium may build up to toxic levels.  Compost that is high in nitrogen sources, such as poultry litter or food wastes, can be high in ammonium and othee nutrients.  Conversely, if there are low levels of nutrients, transplants can be stunted and not perform well in the field. 

Physical Properties  The physical properties of a compost-based mix can also differ from conventional greenhouse potting mixes.  Compost may contain excessive amounts of fine sized particles, so that the mixes hold moisture longer than desired. Compost has a higher bulk density that may be 3 to 4x the bulk density of peat.  (Bulk density is the weight of a given volume of material). High bulk density is an indicator of low porosity and media compaction that may cause restrictions to root growth, and poor movement of air and water through the media. In greenhouse mixes, a low bulk density is desirable.  As organic matter decomposes, it tends to have a small particle size with poor drainage, and low porosity that can adversely affect root growth. Because composts are microbially active, they break down organic matter in the mix, resulting in compacted media.  This compacted media adversely affects root growth.  Compost-based mixed with too many fine particles make it difficult to manage moisture levels in the growing media.   When you water, it may not penetrate the growing media and the media stays wet too long.  Algal scum can then develop on the surface of the growing media. 

Use of Supplemental Organic Fertilizers 

Supplementing pre-plant fertilizers or compost with liquid organic fertilizers is generally required to provide adequate nutrition. Fish fertilizers, made from waste products of the ocean fish processing industry, are thick, heavy liquids which are difficult to use with fertilizer injectors because the concentrate consists of very fine particles in suspension. Dilute solutions develop a strong odor in storage. Because of this, fertilization may need to be less frequent. Application rate will depend on frequency. However, excessive fish fertilizer builds up a nutrient rich scum on the surface of media, leading to algal growth and shore fly proliferation. 

Different fish fertilizers supply plant nutrients at varying levels of availability. Some may be stabilized with phosphoric acid, resulting in a high concentration of readily available phosphorus. Others contain liquid seaweed resulting in a small addition of potassium. Most fish fertilizers contain ammonium nitrogen, which as discussed previously, can be a problem for sensitive transplants such as tomatoes, peppers and eggplants. In New England, the Neptune’s Harvest Brand is the most commonly available fish fertilizer and it is OMRI-approved for organic production.

Some growers use Nature's Source Professional Plant Food 10-4-3 a liquid, “organically-based” fertilizer. The organic portion is oilseed extract. Most of the nutrients, however, are derived from inorganic salts and for this reason it cannot be used for certified organic production.

Several liquid fertilizers used for organic production are derived from plant extracts. The best-known of these has been Nature's Source Organic Plant Food 3-1-1, in which the nutrients are derived from “oilseed extract”. The container has dilution rates expressed in familiar terms for greenhouse growers and has been recommended based on trials at the University of Massachusetts.

Several other liquid organic products are available, such as Biolink 3-3-3 (also an oilseed extract), Converted Organics 3-2-1 (a byproduct of grain fermentation), 1-1-1 Liquid Compost Concentrate and Verdanta PL-2, 2-0-6 (a liquid made from fermented sugar cane and sugar beet molasses). Verdanta would be used as a supplement to use in combination with other fertilizers used for organic production that are low in N or K.

Verdanta EcoVita 7-5-10 (granular) is composed of bone meal, soybean meal, cocoa shell meal, feather meal and fermented sugar cane and sugar beet molasses.

Mixing and application. The fish fertilizers and plant extract fertilizers are sold as concentrates and they must be diluted in water to be safe for plants. Nature’s Source, Bombardier, and Espartan have a pleasant “beer-like” aroma as concentrates, but within 7 days of being mixed with water they “spoil” and develop unpleasant odors. The nutrient value of spoiled fertilizer is unknown and the colonies of bacteria that develop may plug irrigation lines, so diluted fertilizer solution should be used as soon as possible after mixing.

Fish fertilizer has the thickest and least consistent solution and should be agitated before mixing with water. Bombardier and Espartan concentrates are “syrupy” but mix well with water.  Nature’s Source is the thinnest concentrate and it mixes well with water and can pass through fertilizer injectors.

Sustane 8-4-4 and EcoVita are granular fertilizers mixed with the growing medium before planting. These are the easiest organic nutrient source to use in combination with the liquid types.

Fertilizer analysis. Some fertilizers used for organic production supply only one or two of the NPK elements; an example is Bombardier which is 8-0-0. A grower using Bombardier would have to use other fertilizer(s) to supply P and K. One possibility would be Sustane with an 8-4-4 analysis or some other complete NPK granular organic fertilizer.

Nutrient disorders. Plants may develop an overall light green or yellowed color caused by a general nutrient deficiency or more likely, N deficiency. For example, if Sustane is used alone, the symptoms might occur about 45 days after planting, the end of its release time.  This can be prevented by applying an organic liquid fertilizer supplement about 30 days after planting.

Interveinal chlorosis sometimes occurs about halfway through cropping time if plants are only fertilized with some liquid organic fertilizer starting at planting. This chlorosis is most likely caused by an accumulation of too much ammonium-nitrogen in the plant, so-called “ammonium toxicity.” Most greenhouse crops do best with a combination of ammonium and nitrate nitrogen. Unfortunately, fertilizers used for organic production generally don’t contain nitrate-nitrogen. The best approach is to rely on Sustane as the sole source of nutrients for the first month after planting and then start applying Nature’s Source or another liquid organic fertilizer.

Use fertilizers for organic production with caution, on plants you know have exacting nutrient requirements or those prone to foliar chlorosis. Fertilizers should always be tried first on a small number of plants.

Organic Transplant Fertilizer Resources

Cox D. 2016 Plant Response to Nature's Source and EcoVita Organic Fertilizers vs Plantex Chemical Fertilizer. July-Aug. Floral Notes 29(1).
https://ag.umass.edu/sites/ag.umass.edu/files/newsletters/16fnjuly_aug.pdf

Cox D. 2014. Organic Fertilizers - Thoughts on Using Liquid Organic Fertilizers for Greenhouse Plants. Sept.-Oct. Floral Notes 27(2)
https://ag.umass.edu/sites/ag.umass.edu/files/newsletters/14fnseptoct272.pdf

Grubinger, V. 2012. Potting Mixes for Organic Growers. 

https://www.uvm.edu/vtvegandberry/factsheets/OrganicPottingMixes.pdf

Mattson N. 2014. Substrates and Fertilizers for Organic Vegetable Transplant Production. Cornell Greenhouse Horticulture, Cornell University. http://blogs.cornell.edu/greenhousehorticulture/crops-culture/substrates-and-fertilizers-for-organic-vegetable-transplant-production/

Organic Greenhouse Vegetable Production, Potting Mixes for Certified Organic Production, Organic Greenhouse Tomato Production, Plug and Transplant Production for Organic Systems, ATTRA - National Sustainable Agriculture Information Service. http://www.attra.org/horticultural.html#Greenhouse

Organic Potting Mix Basics: eXtension https://eorganic.org/node/3442

Radin, A. 2020. Grow Your Own Seedlings?  Let's talk about the media. URI Cooperative Extension. The Week in Vegetables. February 8, 2020. 

https://web.uri.edu/coopext/files/2-8-20-TWIV.pdf

Seeding and Transplanting

Seeding 

Always purchase high quality seed from a reputable source that is tested for germination rates, uniform emergence and viability. Request the germination percentage for the seed lots that you purchase.  Seeds may also be coated, pelleted, primed or treated with fungicides. Organic growers need to obtain seeds from organic sources whenever possible.  Plan your seedling schedule for your transplant season and keep good records. Most seeds have optimum temperatures for germination. Seeds can be sown in rows in open flats or in plug trays. Some seeds, such as lettuce, need light for germination and should not be covered. Larger seeds can be covered with vermiculate.  Seeds can be sown by hand or with mechanical seeders such as vacuum seeders or needle seeders.  After sowing the seeds, gently mist with tempered, warm water. 

Germination chambers are available from your greenhouse distributor and provide uniformity of temperature and moisture.  Seeds can also be grown on greenhouse benches with bottom heat.  As soon as seedlings develop their first true leaves, they can be transplanted. 

Never store your seeds in the greenhouse for long term storage for their quality can quickly deteriorate due to the high temperatures and relative humidity in the greenhouse. 

Handling Growing Media

How soilless growing media is handled can greatly influence the air space and available water for plant roots. The major goal is to preserve the air space or porosity to insure healthy root growth.

Add water to peat-based mixes before filling plug trays to help create more aeration. Satisfactory filling moisture is achieved if the slightest bit of visible water appears when squeezed between the fingers. Most growers work with a moisture content of 45%-55% by weight. If mixing your own media, thoroughly mix components, but do not over-mix, which will cause particle size to decrease. Over processed media quickly loses porosity, resulting in stunted transplants.

To prevent compaction that encourages damping-off diseases and poor root growth, lightly fill containers, including plug trays, and brush the excess media off the top. Once filled, avoid nesting or stacking trays on top of one another. Stacking containers causes compacted media with reduced air space. This damage cannot be remedied after creating this compaction. Always stagger trays.

When dibbling seed trays, try to avoid compressing the mix; gently press to ensure a small indentation for seeds.

Production Schedules

Starting seeds too soon will result in overgrown transplants of poor quality. An excessively warm greenhouse will cause rapid, spindly growth. The following are guidelines for growing vegetable transplants. Note the number of weeks from seed to transplant. This will vary according to different growing conditions and should serve only as a guide.  It is important for the seedlings to reach the proper level of maturity. Seedlings started too late may not transplant well due to a limited root system.  Overgrown seedlings may have pot-bound roots that do not transplant well. 

Table 17: Germination and Growth of Vegetable Transplants

Crop

Germination Temperature*
(°F)

Optimum Day Production Temperature**
(°F)

Minimum Night Temperature**
(°F)

Approx. No. Weeks to start seeds before Transplant into Field*

Basil

70***

65-70***

62-65***

6

Broccoli

70-80

60-70

50-60

5-7

Cabbage

70-80

60-70

50-60

5-7

Cantaloupe 75-95 70-80 60-70 2-3

Cauliflower

70-80

65-70

55-60

5-6

Celery

70

65-70

55-60

10-12

Cucumber

75-95

70-80

60-70

3-4

Eggplant

75-85

65-80

60-70

8-10

Lettuce

60-70

55-75

45-55

4-6

Onions

65-80

60-70

45-55

8-10

Peppers

75-85

65-80

60-70

8

Tomatoes

75-85

65-80

60-70

6-8

Watermelon

75-90

75-80

60-70

3

References:
* Maynard D.N. and G.J. Hochmuth. 2007. Knott's Handbook for Vegetable Growers. Fifth Edition

* Seed Starting Calculator Johnny's Selected Seeds https://www.johnnyseeds.com/growers-library/seed-planting-schedule-calculator.html
** Lopez, R. 2021.  Producing High Quality and Uniform Vegetable Transplants. 
***2021 Seed Product Information Guide. Ball Seed, PanAmerican Seed, Kieft Seed. https://www.panamseed.com/catalogs.aspx

Note: The greater the difference between daytime and nighttime temperatures, the more stems will elongate. See Managing Plant Height.

Germination Tips for Selected Crops

Warm temperatures and uniform moisture are needed to ensure successful germination and get the plants off to an even start. Many germination chamber systems are commercially available including custom built germination units. It is important to remove flats from the germination chamber as soon as radicles break through the seed coat to prevent seedling stretching.

Growers often use bottom heat or root zone heating to provide warm, even temperatures. Rubber tubing or mats with hot water are placed on the bench top under the plants. A weed mat barrier is placed on the top of the bench to help spread the heat with skirts on the side to help contain the heat. Experience and experimentation with your total seeding system is the key to uniformity and success.

Celery

Celery seeds germinate best at 70°F with continuous light. To prevent bolting, maintain greenhouse temperatures above 55°F.

Cole Crops

To prevent premature seeding or bolting, avoid temperatures below 50°F. The cold temperatures cause the development of premature heads or "buttoning" in cauliflower and broccoli. Any stress or check in growth results in a "wirestem" and plants will not become well established in the field resulting in reduced yields and performance.

Eggplant

Eggplant seed can be directly sowed into 50 cell trays to shorten the time needed to produce transplants by approximately one week. Eggplants are susceptible to chilling injury and should not be grown below 40°F. Any stress or check in growth will result in tough woody stems and transplants that will have a tough time getting started later in the field.

Tomatoes

Exposure of tomato plants to temperature below 60°F will likely result in rough fruit (catfacing) on the first few clusters. Transplant young seedlings into 2"-3" containers when they have two true leaves and grow on until planted in the field. For earliest production, some growers finish their transplants into 6" or larger containers.

Peppers

Germination is very slow at lower temperatures. Seedlings develop well at  65-80°F day and 60-70°F night temperatures. Seeds may be directly sown into 72-cell trays for early production. Peppers are prone to damping off diseases especially if the media is compacted. Jalapeno pepper varieties may require much more time in the greenhouse than bell peppers to achieve adequately size plants.

Cucurbit Crops

Cucurbits do not transplant well, and are best sown in the final container. After germination, excess plants can be thinned. Cucurbit transplants should be field set with a maximum of two true leaves and before plants get leggy when exposed to high daytime temperatures.

Containers for Transplants

Transplants can be grown in all types and sizes of containers. Seeds can be  sown in open seed flats or in single-cell (plug) trays. While many growers may sow seedlings in open flats, tender young roots of young seedlings may be damaged as the seedlings are pulled apart during the transplanting process.  Open flats may also tend to hold unto water (especially depending upon the type of growing media used), so the young seedlings are more susceptible to damping off fungi.   By using plug trays, there will be individual cells for each seedling.  If you have had a problem with young seedlings drying out too quickly, choose plug trays with larger and deeper cells.  Do not hold transplants in plug trays too long, for the young seedlings will stretch and dry out too quickly. 

Before sowing, decide whether germination and finishing will occur in the same container or whether seeds will be sown in one container followed by transplanting to a finishing container.

Plug Trays or Flats 

Germinating and growing small plugs requires close attention to detail and is probably best done by local, specialty propagators. Trays for transplants vary in size from 32 cells to 500 cells. The number of plants in a tray depends on the cell size needed for each plant. Large cell sizes such as 32, 50 or 72 are often used for vine crops and early harvests. Plants are less stressed in larger cells if it is necessary to hold plants for several days before transplanting in the field. Mid-size cell sizes such as 72 and 128 are suitable for tomatoes, peppers, eggplant, and Cole crops. Small cells such as 128, 200 or 288 may be used for lettuce or onions. Consider your available labor, amount of greenhouse space, and the cost and benefit of growing in plug trays or flats in order to make a decision on which size container to use. Plug seedlings should be transplanted as soon as possible after they have reached finished size.

Soil Blocks 

With this method, wet media is pressed into forms to create separate blocks placed into flats.  As the young seedlings grow, their roots reach the edges of the block and are air pruned due to the separation between the blocks.   Young plants may be less prone to transplant shock when planted into the field.  Specialized equipment is needed to make the blocks.  The growing mix needs to contain enough peat, compost and sand or perlite so the material binds together and stays moist. 

Biodegradeable containers

Some growers will produce their vegetable transplants for sale to home gardeners in biodegradeable pots such as coconut husk fiber (coir) pots, fiber or jiffy peat pots or composted manure (Cowpots) pots or 80% wood fiber, 20% peat (Fertil) pots. Cowpots and Fertil pots are OMRI listed.

Care of Purchased plugs: Purchase transplants from a reputable local supplier to minimize the potential of importing severe disease and insect problems that are common in other regions of the country. Open and unpack the boxes immediately upon arrival and check the physical condition of the plants. Inspect plants for root and foliar diseases and for insects and mites. Report any damage or discrepancies immediately to your supplier (most companies want to hear within 24 hours). Photographs are also helpful.

Place plant trays on benches and water thoroughly with plain water (no fertilizer); be sure that plugs on the edges of the trays are thoroughly watered. Plugs can dry out quickly due to the small volume of growing medium; check the trays 2-3 times daily for watering. After the initial watering, apply a general-purpose fertilizer (such as 20-10-20) at 50-60 ppm of nitrogen at every other watering. Allow plants to acclimate to the greenhouse conditions for 24-48 hours before transplanting.

Transplanting to a finishing container: Water the plug trays thoroughly 2-3 hours before transplanting; this aids in removing the plugs from the trays. Prepare your cell packs or pots by filling them with pre-moistened growing medium and pre-dibbled holes for the plugs. Lightly fill containers and brush off excess. To prevent compaction, do not pack down or stack ("nest") filled flats.

Take special care during transplanting to handle plants gently and avoid planting too deeply. Stems of tender seedlings can be easily injured when workers grasp or "pinch" the stems too tightly. This often leads to stem cankers causing plants to wilt and die. Plant plugs at the same depth as the original plug. Some transplants may have elongated stems and it is tempting to bury the stem. Resist the temptation, except for more adaptable tomato plants.

See information under the specific crops for additional information on transplant production and planting.

Plant Culture and Height Management

 

Watering

Handwatering and overhead irrigation systems are the primary methods of watering vegetable transplants. The amount of water and frequency of watering will vary depending on container size, growing media, greenhouse ventilation and weather conditions. Water requirements change as plants grow. The weight of containers is commonly used to determine the moisture level of the media and when to water. Pick up individual containers and if they feel heavy, even though the surface is dry, do not water. If containers are light in weight, even though the surface looks wet, investigate further to make sure the water is thoroughly wetting the media. Tempered water is used by some growers to minimize shocking seedlings with cold irrigation water.

Some growers successfully use a water gauge that measures how much water is used. Some growers use a container placed among the pots to measure the amount of water applied. Experience will dictate how much water is needed to thoroughly saturate a container. Other growers use their finger to feel the media in shallow containers (the surface can be dry, while deep in the pot the media can feel wet).

It is important to water thoroughly, to moisten the entire container, which will promote root growth to the bottom of the container. If this is not done, root growth will develop in the upper part of the container and plants will be more prone to drying and drought stress.  Excessive watering leads to succulent plants and restricted root growth.

Allow plants to dry down before watering, but do not let the plant wilt severely, as this will damage roots. Vegetable transplants should be watered thoroughly early in the day to allow foliage to dry before evening. If foliage remains wet overnight, foliar diseases will develop.

Most commercial mixes contain a wetting agent that provides initial hydration and improves wettability of the mix. Older mixes (stored longer than 8 months) are harder to wet and the addition of a liquid wetting agent may be needed.

 Managing Plant Height

Compact, uniform transplants can be easily handled for planting in the field. Leggy transplants may develop with low light levels, overwatering, overfertilizing or when plants are held for longer than anticipated in the greenhouse due to unseasonable weather conditons. Since very few growth regulators are registered for vegetable transplants, plant height is often managed by increasing light levels, using mechanical stresses such as "brushing" and adjusting temperature, water and fertilizer levels. 

Maximizing Light Levels: Maximizing the amount of light plants receive helps reduce plant stretch. Giving plants adequate space, and replacing plastic coverings as needed helps prevent reduction in light levels.  

Adjusting Temperature (DIF): The greater the difference between daytime and nighttime temperatures, the more plants will "stretch" (stems elongate). When the day temperature is very warm and the night temperature is cool or cold, plants will be taller. If the day and night temperatures are both the same, plants will be shorter than with warm days and cool nights. If the night temperature in the greenhouse is kept warmer than the day temperature by using heating at night and ventilation during the day, the plants will be even shorter. Keeping day temperatures cool (70º F) will help keep transplants shorter. The difference between day minus night temperatures is known as DIF. The critical period during a day for height control using DIF is the first 2-3 hours following sunrise, starting about 30 minutes before sunrise. By lowering the temperature during this 3-hour period by a few degrees, plant height in many vegetables can be managed.  Vegetables vary in their response to DIF. For example, tomato, Cole crops, eggplant and melon are very responsive, while squash, cucumber and pepper are much less responsive.

Mechanical Brushing: Mechanical stress reduces stem elongation. Wind, shaking or brushing are all types of mechanical stress.  Research has shown that mechanical stress reduces stem elongation and maintains plant height. For example, brushing transplants twice daily for 18 days using about 40 strokes back and forth with a cardboard tube suspended from an irrigation boom can result in as much as a 30% reduction in stem elongation. Growers have also successfully used a wand made of plastic plumbing pipe or a flat piece of polystyrene foam. Vegetable plants such as tomatoes, eggplants, cucumbers  and some varieties of broccoli and cabbage have responded to this method of height control. Note that this technique has damaged some tender plant species such as peppers. It can also enhance the spread of bacterial pathogens and cause wounds making it easier for the bacterial pathogens to infect tender young plants.  Brush plants when the foliage is dry and if you see plant damage, reduce the number of times you are brushing the plants. Brushing can improve establishment of transplants in the field. They resume their normal growth about 3 days after the brushing stops.  There is also little or no reported effect on yield.  

Water Stress: Water stress is another tool growers can use to manage plant height. Maintaining plants on the dry side limits cell expansion and plant growth. This method requires close monitoring to avoid permanent damage such as leaf burn or even plant death. One technique is to irrigate the growing mix thoroughly and then allow it to dry to the point where plants wilt before irrigating thoroughly again. Growth is restricted during the period when the growing medium is very dry. Once watered, the plants rapidly resume growth. Experienced tomato growers have successfully used this technique.

Low Phosphorus: Withholding nutrients can also be used to prevent stretching. Low phosphorus fertilization is especially effective for tomatoes. If carefully managed, a mild to moderate phosphorus (P) deficiency may result in a desirable reduction in growth with no foliar symptoms of P deficiency. If this method is used, use a starter fertilizer when transplanting into the field. 

Plant Growth Regulator: A review of pesticide labels indicates that Sumagic (uniconazole) is the only plant growth regulator labeled for use on a limited group of vegetable transplants (tomato, pepper, eggplant, tomatillo, ground cherry, and pepino). Sumagic is a gibberllin biosynthesis inhibitor suppressing plant height by inhibiting internode elongation. It is a particularly active plant growth regulator, so very small concentrations are needed.  Apply Sumagic only as a foliar spray at a rate of 2-10 ppm. As with any plant growth regulator, it is recommended to test growth regulator treatments on a small number of plants with a low rate before full-scale implementation. The maximum cumulative amount of Sumagic applied must not exceed 10 ppm with coverage of 2 quarts per 100 sq. feet. This means that total amount used in sequential applications can only add up to 10 ppm spray (example, two applications at 5 ppm or 4 applications at 2.5 ppm). The last spray must be no later than two weeks after the two to four leaf stage of development. Experiments have shown that sequential applications produce the best results and that the earlier that the plants receive the Sumagic spray, the greater effect it will have on the final height of the transplants. As only a limited number of tomato varieties have been tested, growers are encouraged to do their own in-house trials on a small number of plants with a low rate before full-scale implementation. 

Acclimating or Hardening-Off Transplants

The transition from the greenhouse to the field involves changes in light, temperature and wind. Vegetable transplants benefit by a gradual acclimating "hardening off" period before they are transplanted into the field. Gradual exposure to outdoor growing conditions and reduced watering at the end of the growing period with some protection from wind and temperature but full exposure to light can increase the survival rate of transplants in the field. Three to six days are adequate to acclimate transplants. Larger greenhouse growers may be using roll out benches but smaller growers can use wagons to move transplants into and out of the greenhouses as needed. 

Care must be taken to not "over-harden" young transplants. Cool-season crops exposed to very low temperatures can result in bolting (in cabbage) or buttoning (in broccoli or cauliflower). Warm-season crops generally are hardened at temperatures higher than those of cool-season crops. Cold temperatures can set back warm-season crops and can induce disorders such as catfacing in tomatoes.

Table 18: Scouting and Biological Control Guidelines for Vegetable Transplants

Pest How to Monitor Where to Look Biological Control Options
APHIDS Monitor weekly. Rely on plant inspection, not sticky cards. Look for small, 1/16" long aphids with two cornicles or "tailpipes" at the rear of the body. Identification to species is needed to determine which host specific aphid parasite to release when using biological controls. If uncertain, mixes of different species are available.  Underside of leaves and along stems on tips of new growth  of eggplant, pepper, tomatoes and many different leafy vegetables. Signs of aphid activity: shed white skins, shiny honeydew, presence of ants, curled new leaves, and distorted growth. Adalia bipunctata (predatory lady beetle); Aphelinus abdominalis (aphid parasite); Aphidius colemani (aphid parasite); Aphidius ervi (aphid parasite); Aphidius matricariae (aphid parasite); Aphidoletes aphidimyza (aphid midge, predator); Chrysoperla spp. (green lacewing, predator); Hippodamia convergens (predatory ladybeetle); Aphid Banker Plants (starter)
BACTERIAL LEAF SPOT On peppers, at first, chocolate-brown spots are less than 1/4" in diameter, and water-soaked in appearance. Severely spotted leaves appear scorched and defoliation may occur. Some strains also cause leaf spot on tomatoes.

Seed-borne disease.

More prevalent during moderately high temperatures, long periods of high humidity and leaf wetness.

 
BOTRYTIS BLIGHT Look for leaf blight and tan stem cankers. Botrytis blight produces characteristic gray fuzzy-appearing spores on the surface of infected tissues during humid conditions. In areas where plants are spaced close together and with leaf wetness and condensation dripping from plastic greenhouse coverings. Biological fungicides: Bacillus amyloliquefaciens; Bacillus subtilis; Gliocladium catenulatum;  Pseudomonas chloraphiis; Reynoutria sachalinensis extract; Streptomyces sp.; Streptomyces lydicus; Ulocadium oudemansii
BROAD MITES Look for symptoms of damage: leaf edges curling downward, twisted and distorted growth. With a 20x hand lens, or under a dissecting microscope, look on underside of leaves, especially on newest growth, for broad mites and their distinctive eggs. Near ornamental crops affected with broad mites. Near whteflies (broad mites may hitch a ride on whiteflies). Peppers are especially susceptible. Amblyseius swirskii (predatory mites); Neoseiulus (Amblyseius) californicus (predatory mites); Neoseiulus (Amblyseius) cucumeris (predatory mites).
CATERPILLARS Inspect plants when adult moths are active, especially near Cole crops. Look for caterpillars, their feeding damage and frass. Inspect plants near doors, openings, weedy areas and in greenhouses near vegetable fields. Bacillus thuringiensis subsp. kurstaki; Trichogramma spp. (egg parasite).
CYCLAMEN MITES Look for symptoms of damage: inward curling of leaves, puckering and crinkling. With a 20x hand lens or under a microscope, look within buds for mites and their eggs. Near ornamental crops affected with cyclamen mites. Amblyseius swirskii (predatory mites); Neoseiulus (Amblyseius) californicus (predatory mites); Neoseiulus (Amblyseius) cucumeris (predatory mites).
DAMPING OFF (Pythium root and stem rot) Monitor seed flats of susceptible plants. Inspect weekly. Visually examine roots for cortex that sloughs off leaving central core. Inspect plants weekly for signs of disease: wilted, stunted, off-color plants with discolored root systems. Focus on areas where plants stay wet, or where there may be high populations of shore flies that may carry disease spores. High soluble salts/fertility increases susceptibility. Biological fungicides: Bacillus amyloliquefaciens; Bacillus subtilis; Gliocladium catenulatum; Gliocladium virens; Pseudomonas chlororaphis; Reynoutria sachalinensis extract; Streptomyces grisioviridis; Streptomyces lydicus; Trichoderma aperellum & T. gamsii; Trichoderma harzianum; T. harzianum & T. virens.
DAMPING OFF (Rhizoctonia root and crown rot) Monitor seed flats of susceptible plants including Cole crops, peppers, and tomatoes. Look for small, water-soaked spots on stems or leaves before seedlings collapse. Seed flats near walkways or near dust and debris. Overcrowded seedling flats are more susceptible to damping off. Biological fungicides: Bacillus amyloliquefaciens; Bacillus subtilis; Gliocladium catenulatum;  Gliocladium virens, Pseudomonas chlororaphis, Reynoutria sachalinensis extract, Streptomyces grisioviridis; Streptomyces lydicus; Trichoderma aperellum & T. gamsii; Trichoderma harzianum; Trichoderma harzianum and T. virens
FUNGUS GNATS Use sticky cards to monitor for adults. Place cards horizontally above soil surface. Potato chunks can be used to monitor for larvae. Check every two days. Favorable habitats include areas with standing pools of water, mud floors, spilled media, and weeds. Bacillus thuringiensis subsp. israelensis (pathogen); Dalotia coriaria (predatory beetles); Stratiolaelaps scimitus (predatory mites); Steinernema feltiae (nematodes)
LATE BLIGHT Look for sunken, water-soaked lesions on leaves and brown lesions on tomato stems or on potato bedding plants. Overwinters in potato cull piles or outdoors in field soil that is not completely frozen, so is not generally considered a problem for locally grown tomato transplants.  
LEAFMINERS
(Spinach and beet leafminers)
Look for small, oblong, white eggs that are laid in neat clusters on the undersides of the leaves. Inside the mines look for one or several pale, white maggots. Scout undersides of leaves (beets, spinach, Swiss chard) for eggs and treat when they are first observed in order to target larvae as they hatch. The wasp parasitoid, Diglyphus isaea, which is most often used against Liriomyza leafminers (see Celery section) has also been reported to control leafminers in chard and  works best in warm weather.
POWDERY MILDEW Scout weekly. Look for faint, white fungal threads and spores on leaves. Scout near vents, or any location with a sharp change between day and night temperatures.  Biological fungicides: Bacillus amyloliquefaciens; Bacillus subtilis;  Reynoutria sachalinensis extractStreptomyces lydicus.
SHORE FLIES Use yellow sticky cards to monitor for adults. Found near algae, their food source. Black frass flecks the leaves. Larger than thrips frass. Dalotia coriaria (predatory beetles); Steinernema carpocapsae (nematodes).
SLUGS Look for chewed holes in leaves and shiny patches of slime. Slugs hide under dense foliage, beneath pots and benches and in other protected locations. Chewed, irregular holes with smooth edges in leaves and slime that dries into silvery trails on foliage.  
SPIDER MITES (Two-spotted spider mites) Rely on plant inspection. Look for light flecking, speckling or discolored foliage, and webbing if high populations have developed. Look in hot, dry locations in greenhouse (i.e., near furnace) or near entrance ways. Amblyseius andersonii (predatory mites); Feltiella acarisuga (predatory midge); Neoseiulus (Amblyseius) californicus (predatory mites); Neoseiulus (Amblyseius) fallacis (predatory mites); Phytoseiulus persimilis (predatory mites).
THRIPS (Western flower thrips) Rely on sticky cards (placed just above crop canopy) and foliage inspection of key plants for early detection and to evaluate treatments.  Inspect plants by tapping tender new growth over a sheet of white paper. Watch for curled emerging leaves, distorted new growth on pepper. Look for white scarring and black frass (size of pin point) on cucumber and eggplant. Amblyseius swirskii (predatory mites); Dalotia coriaria (predatory beetles); Neoseiulus (Amblyseius) cucumeris (predatory mites);  Orius spp. (pirate bug, predator); Steinernema feltiae (nematodes); Stratiolaelaps scimitus (predatory mites); ornamental pepper banker plants "Purple Flash" and Lobularia for Orius.
TOBACCO MOSAIC VIRUS  Dark line patterns and distortion of leaves.  Spread by plant handling (no insect vector).   

TOSPOVIRUS
Impatiens
Necrotic spot virus (INSV)

& Tomato spotted wilt virus (TSWV)

Symptoms will vary depending upon the host. On pepper, look for necrotic spots on the leaf. Ringspots may also develop. On tomato, leaves may develop small, dark brown spots. Thrips populations may be highest at front and rear of the greenhouse. Use fava bean or petunia indicator plants to determine if thrips are carrying the virus. Symptomless weeds may also be a source of virus. None. See thrips.
WHITEFLIES Rely on plant inspection to detect immature stages. Use sticky cards to monitor for adults. Egg laying adults are found on the uppermost tender leaves of tomatoes, eggplant, and leafy greens. Immature stages are found on the undersides of leaves. Amblyseius swirskii (predatory mites); Chrysoperla spp. (Green lacewing, predator); Delphastus pusillus (catalinae) (predatory beetles);  Dicyplus hesperus (predatory bug), Encarsia formosa (Greenhouse whitefly parasite); Eretmocerus eremicus (Sweetpotato whitefly parasite).

 

Transplant Disease Management

Introduction

There are a limited number of fungicides labeled for greenhouse-grown vegetable bedding plants compared to ornamental bedding plants. Integrated pest management (IPM) offers a practical way to effectively manage pests on vegetable bedding plants and transplants. Through the use of sound cultural practices, monitoring techniques, accurate problem identification, and timely implementation and evaluation of appropriate management strategies, growers can improve their production while minimizing their reliance on routine pesticide applications. IPM utilizes many different management options; genetic, cultural, physical, mechanical, biological and chemical. Routine crop inspection alerts growers to developing pest and cultural problems while they are still minor and can be easily managed. Early detection and intervention is the foundation of an IPM program. Use Table 18 (page 51) to learn scouting practices for insect and disease pests which have effective biological control options.

Diseases of vegetable transplants include Botrytis blight, damping-off, Alternaria blight, late blight, powdery mildew, downy mildew, bacterial diseases such as bacterial leaf spot, bacterial canker, and black rot, and viral diseases such as Cucumber Mosaic Virus (CMV), Tobacco Mosaic Virus (TMV), and Tospoviruses. Effective management of diseases requires accurate identification. Failure of disease control is often because the cause was not accurately identified. Symptoms caused by poor cultural practices can also mimic disease symptoms. Fungicides cannot correct problems caused by high soluble salts, poor aeration or a nutrient imbalance. An integrated approach to disease management involves the use of resistant cultivars, sanitation, sound cultural practices and the proper use of the correct pesticide.

Resistant Cultivars

Seed catalogues often feature disease-resistant and tolerant varieties of vegetables. Utilize resistant varieties where feasible, but take some time to research the diseases that are giving you the most trouble to find other strategies to incorporate into the disease management plan.

Seed Treatments for Disease Management

Seed treatments are useful for many vegetable crops to prevent root diseases, as well as certain diseases carried on or within the seed. There are two general types of seed treatment: eradicative and protective. Eradicative seed treatments use hot water or chlorine to kill disease-causing agents on or within the seed. They are useful in controlling certain seed-borne bacterial diseases such as bacterial leaf spot on pepper and tomato and bacterial canker on tomato. Protective seed treatments use fungicides on the seed surface to protect the seed against decay and soil-borne organisms such as damping off caused by Pythium, Phytophthora and Rhizoctonia. For more information regarding seed treatments, contact your seed sales representative, Extension vegetable specialist, or plant pathologist and see the section on Hot Water Treatment of Seed under Disease Management.

Sanitation

Pest management on vegetable transplants begins with a clean, weed-free, disinfected greenhouse. Before growing the crop, the greenhouse should be cleared of plant debris, weeds, flats and tools. Empty benches, potting tables, storage shelves, tools and cell packs should be washed and disinfected with a sanitizing agent. It is important to thoroughly clean or power wash to remove organic debris from plastic containers before using a sanitizing agent. Bits of organic debris can be difficult to remove and the organic matter can be a source of disease causing pathogens if the containers are reused.

After the greenhouse has been sanitized, care must be taken to avoid recontamination with pathogens. Purchase certified, disease-free seed from reliable sources. If possible, purchase seed that has been disinfested by chemical and/or heat treatment by the seed company. Potting media is easily re-infested by dirty hose nozzles or tools and unsanitary growing conditions. The floor of the greenhouse is a source for many root rot diseases. Use a hook to keep the hose nozzles off the floor. Grow transplants off the ground in a well-ventilated greenhouse. To prevent root rot diseases, avoid over-watering and over-fertilizing. Water early in the day to allow foliage to dry quickly to help prevent foliar diseases.

Use separate greenhouses for vegetable seedlings and ornamental bedding plants. Separate greenhouses: 1) will protect vegetable seedlings from insect pests that may migrate from ornamentals and plants that are held over; 2) will help protect vegetable seedlings from tospoviruses (i.e. tomato spotted wilt virus and impatiens necrotic spot virus ) due to migrating infected thrips; 3) protect vegetable transplants from diseases that ornamentals may also be susceptible to (i.e. curcurbit seedlings from powdery mildew on calibrachoa and petunia and some cultivars of verbena) or tomato transplants from late blight on petunias); and 4) facilitate treatment of the vegetable seedlings if pesticides are needed.

Keep tomato transplant production separate from greenhouse tomato fruit production. Greenhouses with both young transplants and mature plants increase the risk of perpetuating diseases.

Techniques to Reduce High Humidity

High relative humidity is one of the major contributing factors to Botrytis blight and powdery mildew, common fungal diseases of bedding plants. Warm air holds more moisture than cool air. During warm days, the greenhouse air is more humid. As the air cools in the evening, the moisture-holding capacity drops until the dew point is reached. Water then begins to condense on surfaces. Humidity can be reduced by exhausting the moist air and replacing it with cooler outside air that is drier. The method and time it takes to heat and vent depend upon the heating and ventilation system in the greenhouse. In greenhouses with vents, turn the heat on and crack the vents open about one inch. The moist humid air escapes from the vents. In greenhouses with fans, activate the exhaust fans for a few minutes and then heat the greenhouse to raise the air temperature. Then, shut off the fans. A clock can be set to activate the fans. The cooler, outside air will lower humidity levels as it is warmed in the greenhouse. A relay may be needed to lock out the furnace or boiler until the fan shuts off so that flue gases are not drawn back into the greenhouse. This will also help to prevent damage from ethylene or sulfur dioxide to sensitive seedlings. Heat and vent two or three times per hour in the evening after the sun goes down and early in the morning at sunrise. Heating and venting can be effective even if it is cool and raining outside.

Air movement, even in a closed greenhouse, helps reduce moisture on the plant surfaces and surrounding the plants. Using horizontal airflow (HAF) can also reduce condensation. HAF fans keep the air moving in the greenhouse, helping to minimize temperature differentials and cold spots where condensation occurs. Air that is moving is continually mixed. The mixed air along the surface does not cool below the dew point so it does not condense on plant surfaces.

HAF fans are more efficient than low-cost residential home fans, which are generally not designed for greenhouse conditions.

In addition, cultural practices can be used to reduce humidity within the plant canopy. These include proper watering practices and spacing of plants. Since most vegetable transplants are grown in flats that are spaced flat to flat, reducing humidity within the canopy is difficult. Proper planting dates, plant nutrition, watering practices, and height management techniques help to prevent lush, overgrown plants, thereby reducing humidity within the canopy.

Always water in the morning to reduce the length of time the leaves stay wet after irrigating to prevent foliar diseases. Rising temperatures during the day will evaporate water from the foliage, so the leaves stay dry. Avoid watering late in the day or when water will sit on leaf surfaces for long periods of time.

Fungicides and Bactericides

Fungicides can provide excellent management of some diseases, but for others, they may be ineffective. In general, to control root diseases, broad-spectrum fungicides or preventive biological fungicides should be applied as a drench on a preventative basis. Read directions for application on pesticide labels. An application of additional water may be necessary. For foliage diseases, obtain thorough spray coverage and treat when the disease is first evident.

Biological Control Agents

Biological control of plant diseases is the suppression of disease by the application of one or more biological control agents (BCAs).  These beneficial BCAs include microorganisms such as specialized fungi bacterial and actinobacteria (filamentous bacteria).  Researchers have isolated specific strains of these organisms, many of which occur naturally in soils.  The commercial products have been developed from these various strains and formulated with additives to enhance their performance and storage. 

BCAs or biofungicides include living organisms that are best used preventively before disease occurs and not as rescue treatments for already diseased plants.   They should always be combined with proper sanitation and other cultural practices that promote plant health.    Biological fungicides may suppress diseases in a number of different ways, including direct competition or exclusion, antibiosis, predation or parasitism, induced resistance, and plant growth promotion. Many biological fungicides work in multiple ways, such as by competition and parasitism, so are less likely to develop resistance than conventional fungicides, especially those that work in a single way  (single-site fungicides) with a specific mode of action. 

Direct Competition/ Exclusion: Before root infection can occur, pathogens must gain access to the zone closely associated with the root, known as the rhizosphere. For foliar diseases, the pathogen must make contact with the leaf or flower zone. The biofungicide grows a defensive barrier around this root, leaf or flower zone. The beneficial microbes compete with plant pathogens for nutrients, infection sites, and space, excluding the pathogen. 

Antibiosis: The BCA produces chemical compounds or secondary metabolites such as antibiotics or other toxins that kill the target organism.  The BCA  produces compounds that inhibit fungal or bacterial spores from germinating and causing plant disease or produces compounds restrict the pathogen’s growth.

Predation or Parasitism: The BCA attacks and feeds on the pathogen, producing cell wall degrading enzymes, inhibiting or killing the pathogen. 

Induce Resistance to the Host Plant: The BCA triggers the host plant to turn on its own defense mechanisms. These plants produce chemcials that travel to other parts of the plant and act as signals to activate natural defense mechanisms. This process, known as systemic acquired resistance (SAR) or induced systemic resistance (ISR), improves the plant's response to pathogen attacks by initiating the metabolism of plant defense compounds. 

Plant Growth Promotion: The BCA promotes enhanced root and shoot growth in the absence of disease-causing pathogens. There may be increased nutrient availability of iron and other micronutrients by changing the pH or enzymes to help break down insoluble nutrient elements. 

Benefits of Biological Fungicides

  • Reduced risks to applicators and the environment.
  • Shorter re-entry intervals and days to harvest intervals than many conventional fungicides.
  • Many are labeled for use on edible crops, including herbs and vegetables.
  • Most (not all) are OMRI approved for organic production. Check company labels or websites or see the OMRI website at www.omri.org
  • Less chance of plant injury, but not always, so consult product labels.
  • Generally compatible with beneficial predators and parasites (natural enemies), and beneficial nematodes (check company websites for more information).
  • Improved uptake of certain nutrients.
  • Can be used in rotation with conventional chemicals to reduce the risk of pathogens developing resistance to conventional fungicides.

Limitations of Biological Fungicides

  • Must be used preventively, for they will not cure diseased plants.
  • Must be used with proper cultural controls for plant growth, including starting with a clean growing environment and clean plants. 
  • Must be used with strict sanitation protocols.
  • Shelf life is shorter than conventional fungicides and needs to be stored under proper conditions to avoid BCA mortality.  (consult labels). 
  • May need to be re-applied more often than conventional fungicides

A number of products are commercially available for use on vegetable transplants. See Table 19 for information on labeled crops and diseases for these biological fungicides.

Fungal Diseases

Basil Downy Mildew

Downy mildew (Peronospora belbarhii) is a problem on basil (grown in the greenhouse and in the field). It was first reported in Florida in 2007 and has been found in New England since 2008. Sweet basil cultivars are very susceptible to downy mildew with the least susceptible basils including the lemon, Thai, and spice types. 

Symptoms: Infected leaves develop a diffuse yellowing that is easily confused with nutrient deficiency. Distinct vein bounded patches on the underside of the leaves develop that produce dark purple-brown sporangia. The fuzzy, dark growth makes leaf undersides appear dirty.

Management: Management of environmental conditions such as temperature, humidity, and duration of leaf wetness, sound cultural practices, and fungicides will help prevent disease development. The pathogen needs at least 6 hours of leaf wetness and at least 12 hours for severe infections to develop. The optimum temperature for basil downy mildew to develop is 68º F, with no basil downy mildew growth below 53º F or above 77º F.

  • Start with disease-free seed. Ask if your supplier is steam treating their basil seed. (Basil seed produces a gelatinous exudate, so it is difficult to use hot water seed treatments).
  • Buy seed from a trusted source.  Talk to your supplier about how the seed was produced, if it has been tested. The pathogen may be seed borne, but the mechanisms involved are not well known, and testing is difficult.
  • Purchase basil downy mildew resistant varieties such as Amazel, Prospera, Rutgers Obsession DMR for both field and potted plant production, Rutgers Devotion DMR for potted plant production, and Rutgers Thunderstruck DM for field production.  None of these varieties are fully resistant but will develop the disease more slowly than fully susceptible varieties. 
  • If you purchase plugs or transplants, inspect them carefully upon arrival.
  • Monitor plants at least once a week. Inspect plants in areas where the air movement is the lowest, such as the central part of the greenhouse or the middle of benches.
  • It is vital to reduce humidity and leaf wetness duration to prevent spore germination. See Techniques to Reduce High Humidity, page 52. 
  • Provide good air circulation and reduce humidity within the canopy. Proper planting dates, fertility, watering, and height management will prevent overgrown plants, reducing humidity within the canopy.
  • Water in the morning, never late in the day. Rising temperatures during the day will cause water to evaporate from the foliage and dry the leaf surface.
  • Consider use of sub-irrigation or bottom watering to keep leaves dry.
  • If fungicides are used, they must be applied preventatively on a regular schedule before plants are infected. If contact fungicides are used, thorough coverage is needed to the underside of the leaves.
  • If you see symptoms of downy mildew, immediately destroy the infected plants, and clean and sanitize the greenhouse.
  • After you discard the infected plants in a closed plastic bag,  protect adjacent plants with fungicides.
  • Plan on planting and harvesting basil early.

For Garden Retailers: Dr. Meg McGrath, Cornell University, suggests encouraging home gardeners to grow some plants in containers that can be brought inside when humidity outside is high (overnight and on rainy days). The pathogen needs at least 85% humidity to be able to infect.

Botrytis blight

Botrytis can cause leaf blight, stem cankers, damping off, and root rot. Plants may be attacked at any stage, but the new tender growth, freshly injured tissues, and dead tissues are most susceptible.

Symptoms: Botrytis blight produces characteristic gray fuzzy-appearing spores on the surface of leaves and stems. Young leaves may become infected and then progress to the stem, with tan stem cankers developing on basil and tomato.

Air currents and splashing water can easily disseminate the spores. In general, germination of spores and infection is dependent on a film of moisture for 8-12 hours, relative humidity of 93% or greater, and temperatures between 55° and 65°F. After infection, colonization of plant tissues can occur at temperatures up to 70°F.

Management: Botrytis diseases can only be managed by a combination of methods, including manipulation of environmental conditions (temperature, humidity, and duration of leaf wetness), sound cultural practices, and the use of fungicides. Fungicides alone cannot control Botrytis, and this pathogen has a long history of fungicide resistance development.

  • Control weeds and remove plant debris before and during production.
  • Dispose of diseased plants and debris in a plastic trash bag. Keep the bag closed to help prevent spreading spores to uninfected plants as the bag is removed from the greenhouse. Cover trash cans to prevent the airborne spread of spores from diseased plant tissue.
  • Reduce humidity and leaf wetness duration to prevent spore germination. See Techniques to Reduce High Humidity, page 52. Provide good air circulation and reduce humidity within the canopy.
  • Proper planting dates, fertility, watering, and height management will prevent overgrown plants, reducing humidity within the canopy.
  • Water in the morning, never late in the day. Rising temperatures during the day will cause water to evaporate from the foliage and dry the leaf surface.
  • Avoid growing ornamental hanging baskets above vegetable transplants. Spent flowers dropping on plants below cause Botrytis infection.

Damping-off of Seedlings

Damping-off is a common disease of germinating seeds and young seedlings. Several fungi are capable of causing damping-off, including Rhizoctonia, Alternaria, Sclerotinia, and the water molds, Phytophthora, and Pythium. Soil-borne fungi generally do not produce air-borne spores but are easily transported from contaminated soil to pathogen-free soil by infected tools, hose ends, water-splash, and hands. Young seedlings are most susceptible to damping-off. However, later in the crop cycle, the same pathogens may cause root and stem rot.

Symptoms: Symptoms of damping-off include seedlings failing to emerge or wilting, often with a stem lesion that appears water-soaked or dark, necrotic, and sunken at the soil line. Pathogens usually spread radially from a central point of origin so plants often die in a circular pattern. Vegetable seeds that are germinated in poorly drained, cool soils are especially susceptible. Young plants that do emerge are weak and often wilt at or below the soil line. Cabbage, cauliflower, tomato, and pepper seedlings may be girdled by brown or black sunken cankers. Stems of these plants may shrivel and become dark and woody (wirestem or collar rot). The plants may not collapse, but remain stunted and die after transplanting.

Management: Damping-off must be prevented because it is difficult to stop once symptoms occur. There are several strategies to prevent damping-off.

  • Use only certified disease-free seed from reputable seed companies.
  • Use fungicide-treated seed. Certain fungicides are labeled for damping-off for selected vegetable crops.
  • Use pasteurized soil, properly produced compost-based or soilless mixes. Apply biological fungicides as a drench at planting or incorporate into the media. Growing media with biofungicides already incorporated into the mix is also commercially available. 
  • Disinfect all flats, cold frames, pots, and tools.
  • Germinate seed under conditions that will ensure rapid emergence, using bottom heat.
  • Avoid overwatering, excessive fertilizer, overcrowding, poor air circulation, careless handling, and planting too deeply.
  • Fill flats with pre-moistened growing media to avoid compaction. Lightly fill and brush containers. Do not pack young plants into containers, use pre-dibbled holes for transplants.
  • To avoid compaction, do not stack or "nest" filled trays or pots.
  • Provide adequate light for rapid growth.
  • Apply biological fungicide as a drench at planting or incorporate into the growing media
  • Discard entire infected flats.

Late Blight

Late blight is caused by the water mold Phytophthora infestans. This fungus-like organism typically overwinters in potato cull piles or in soil where plant tissue has not completely frozen and is not considered a problem for locally grown tomato seedlings. However, the disease can be a problem on potato bedding plants. Late blight is not seed borne in tomatoes but can be carried on potato tubers used for bedding plant production. Petunia and tomato are in the solanaceous family and are susceptible to late blight. Using drip irrigation of petunia hanging baskets helps to minimize long periods of leaf wetness which is conducive to late blight.  In addition, in order to decrease the possible spread of late blight from one host to another, petunia and tomato should not be grown in close proximity (avoid placing hanging basket petunias over tomatoes and grow bench crops in separate greenhouses). 

Symptoms: Common symptoms on tomatoes and potatoes are sunken, dark green or brown, water-soaked lesions on leaves, and brown lesions on stems. White fuzzy growth sometimes develops under moist conditions. Leaf lesions begin as irregularly shaped olive-green to brown spots and quickly grow larger – spots that are consistently small are most likely Septoria leaf spot. Confirm late blight by submission of a sample to a diagnostic laboratory.

Management: Oomycete-specific fungicides are required to manage late blight.  Often treatments begin when the disease is reported nearby because it travels so quickly.

Powdery Mildew

Powdery mildew may occasionally occur on vegetable transplants including tomato, eggplant and other solanaceous crops, as well as cucurbit crops. Faint, white mycelium may develop on leaves and stems, with yellow margins.

Most growers are familiar with powdery mildew when it develops on cucurbits in the field. The powdery mildew that affects certain cultivars of calibroachoa, petunia, and verbena can also infect curcurbit seedlings, including squash, cucumber, and pumpkin. Growers who produce curcurbit transplants as well as calibroachoa, petunia and verbena should be especially careful to separate these crops.  Fortunately, powdery mildew resistant verbenas are commonly available. It is possible that this powdery mildew could affect the cucurbit transplants that may not have otherwise become infected until the fruit was beginning to form in the field.

Bacterial Diseases

Bacterial diseases of vegetable transplants, such as bacterial leaf spot of pepper and tomato, bacterial speck & bacterial canker of tomato, and black rot on Cole crops are introduced into a greenhouse through infected seed and transplants.

Bacterial canker

Symptoms: Bacterial canker of tomato is caused by Clavibacter michiganensis pv. michiganensis (formerly Corynebacterium michiganense). In New England, bacterial canker occurs less frequently than other tomato diseases but it is potentially more destructive. The bacterium is seed-borne but may survive on plant debris in soil for at least one year. It can also survive in the greenhouse on wooden stakes and flats. Wilt, leaf scorch, canker, pith necrosis and fruit spot may occur singly or in combination depending on the circumstances. When the bacterium is carried in the seed, the vascular system becomes colonized, resulting in wilt, pith necrosis and external cankers. Wilt initially occurs on one side of a leaf or one half of a plant because only a portion of the vascular system is blocked. Cankers and pith necrosis occur in later stages of disease development. Cankers are dark and water-soaked in appearance and often exude bacteria that are easily spread to adjacent plants. Pith necrosis is first evident as a darkening of the center of the stem that soon becomes chambered or hollow. When leaf scorch occurs, the petioles usually bend downward while the leaf edges curl up. The margins of the leaves become brown with a yellow border to the inside. Scorching of the foliage often develops in the absence of wilt or stem canker. Transplants may not express symptoms until six to eight weeks after infection, and initial symptom expression is accelerated by environmental stress.

Bacterial leaf spot, Bacterial speck

Symptoms: Bacterial leaf spot is caused by Xanthomonas campestris pv. vesicatoria and is found primarily on peppers although all aboveground parts of tomatoes are also susceptible. Spots on leaves are chocolate-brown with yellowing at lesions' margins, and irregularly shaped with areas of dead leaf tissue. At first, the spots are less than 1/4 of an inch in diameter. Severely spotted leaves will appear scorched and defoliation may occur. This disease is most prevalent during moderately high temperatures and long periods of leaf wetness.

Bacterial speck occurs on tomato but not pepper. The bacterium, Pseudomonas syringae pv. tomato, causes small black spots to develop resulting in chlorosis (yellowing), necrosis (dead tissue) and blighting of the foliage. Bacterial speck can usually be distinguished from bacterial spot by the size of the lesions, however, in some cases, the symptoms look similar.

Black rot

Symptoms: Black rot, caused by the bacterium Xanthomonas campestris pv. campestris occurs where cruciferous plants are grown. All brassicas can be severely affected. The bacterium enters the leaves by colonizing the hydathodes (water pores) and moves from the leaf margins inward. Lesions may also begin at wounds. Diseased tissue is often V-shaped; flaccid, tan to yellow, and with blackened veins. The blackened veins are diagnostic and are best seen by holding the leaf up to the light. When the lesions reach the petiole and stem, the bacterium moves systemically through the plant, resulting in premature leaf drop. At this stage of the disease, a cross-section of the stem will reveal a ring of discolored vascular tissue.

Management of bacterial diseases: These bacteria can be introduced on infected seeds, infected transplants purchased from another operation, or in the field on crop residues. For example, black rot can survive on weeds in the same family as the host crop especially, mustard, shepherd's-purse, and cruciferous weeds. Bacteria enter wounds created by insects, so keep insect pests under control. The management of these bacterial diseases is similar and includes the following strategies:

  • Buy certified disease-free seed from a reputable source.
  • Use hot water-treated seed. Ideally, the seed should be custom-treated by the seed company. Seed companies may treat the seed upon request. There is a risk that germination percentages will be reduced if the seed crop is grown under stressful environmental conditions.
  • Promptly remove infected plants and adjacent plants to prevent further infection and avoid unnecessary handling of plant material.
  • Avoid overhead irrigation, splashing or periods of extended leaf wetness.
  • Disinfect all benches, equipment, flats and stakes.
  • Follow sound practices for weed and insect control.
  • Prevent bacterial leaf spot on peppers by choosing resistant varieties whenever possible. There are many resistant varieties of bell peppers available, but few resistant specialty peppers.

Viral Diseases

Some viral diseases of vegetable transplants include cucumber mosaic virus (CMV), tobacco mosaic virus (TMV), and tospoviruses, INSV and TSWV. There is no control for plants infected with a virus. It is important to have the virus disease accurately identified. Serological techniques such as ELISA (enzyme-linked immunosorbent assay) are now available to accurately identify a wide range of viruses. On-site grower kits using this same technology are also available from Agdia (www.agdia.com) to test for viruses such as CMV, TMV, INSV, and TSWV.

Cucumber mosaic virus

Cucumber mosaic virus (CMV) has a wide host range of over 400 species of plants, including vegetables, ornamentals, and weed hosts.

Symptoms: Infected plants may show mild mosaic patterns and mottling, flecking, and fern leaf distortion.

CMV is primarily spread by aphids that can acquire the virus in as little as 5 to 10 seconds. Aphids then move the virus from plant to plant for a few hours.

Management: Rogue diseased plants. Eliminate weeds such as common pokeweed, chickweed, field bindweed, yellow rocket, and bittersweet nightshade that may be reservoirs of CMV.

Tobacco Mosaic Virus (TMV)

TMV has a wide host range but is especially a concern on solanaceous crops. In recent years, TMV has been reported on pepper, calibrachoa, petunia, and tomato. TMV is not transmitted by insects! It is a very stable virus that can be spread by contact. Workers can easily spread TMV when they handle plants or when cutting tools become contaminated. TMV can persist in dried tobacco leaves, so tobacco products can also be a source of TMV.

Symptoms: Symptoms include yellow mottling, upward leaf curling and overall stunting. Some infected plants may not show any symptoms at all.

Management: Discard infected plants including roots, plant debris, potting media and associated plastic tags. Wear disposable gloves and discard gloves immediately afterwards. Carry the sealed plastic bags directly out of the greenhouse. Do this at the end of the working day.  Disinfect hands by washing with milk, or tri-sodium phosphate and then thoroughly with soap and water. Smokers need to wash their hands before entering the greenhouse so they do not infect plants. In greenhouses, hard surfaces such as door knobs, or flats can become contaminated after handling virus-infected plants and remain a source of infection. Thoroughly disinfect the growing area with a commercial disinfectant. A 20% solution of non-fat dry milk can be used to wash contaminated hands or tools. Control perennial weeds in the Solanaceous family such as ground cherry and horsenettle that could be reservoirs of TMV.

Tospoviruses

Tospoviruses are a group of viruses that include impatiens necrotic spot virus (INSV) and tomato spotted wilt virus (TSWV). They may infect hundreds of plant species including basil, tomato, pepper, and eggplant. These viruses are primarily spread by the western flower thrips. Tospoviruses are not seedborne but are brought into the greenhouse on vegetatively propagated ornamental plants or seedlings that have been exposed to the virus. Once the thrips in the greenhouse become infected, they can transmit the virus to susceptible crops and weeds.

Symptoms: Symptoms include stunting, foliar ringspots and black lesions on stems. Symptoms of INSV and TSWV will vary depending upon the host.

Management: To manage tospoviruses, it is necessary to discard infected plant material, including weeds and to manage thrips. Infected vegetable transplants planted into the garden or field will be stunted and will not produce a harvestable crop. Since INSV and TSWV are not seed-borne, vegetable transplants may be kept free of tospoviruses if they are not brought into contact with other infested crops or thrips carrying the virus. Growers attempting to concentrate all their warm temperature crops in a single house run a risk of mixing tospovirus-free vegetable seed crops with leftover ornamental stock plants or new cuttings that may carry the virus. Pre-finished or vegetatively propagated ornamentals from another producer could be infested with thrips or a virus. Therefore, vegetable bedding plants and ornamentals should always be grown in separate greenhouses.

Table 19: Fungicides and Bactericides Labeled for Vegetable Transplants

Fungicide Target DISEASES Labeled Crops Comments
azoxystrobin
(Heritage) REI 4h, Group 11
Leaf spots and blights, downy mildew, Botrytis blight, powdery mildew (depending upon crop, see label). Cole crops, bulb vegetables, cucurbits, leafy vegetables, and fruiting vegetable transplants. Preventative and curative broad-spectrum fungicide. 
azoxystrobin & benzovindiflupyr
(Mural) REI 12h, Group 11 and 7
Leaf spots and blights, downy mildew, powdery mildew, rhizoctonia stem rot (depending upon crops, see label). Vegetable transplants grown for resale to consumers: cucurbits, and fruiting vegetables. Broad-spectrum fungicides for foliar applications (with translaminar activity) for plants grown for resale to consumers with preventative, systemic and curative properties.
Bacillus amyloliquefaciens D747
(Double NickelOG, Triathlon BAOG)
REI 4h, Group BM02
Fungal & bacterial leaf spots and blights, downy mildew, powdery mildew, damping off  (Pythium, Rhizoctonia, Fusarium, Phytophthora) (depending upon the crops, see labels). Cole crops, bulb, cucurbit, fruiting and leafy vegetable transplants. Broad-spectrum, preventative biological fungicides/bactericides. Begin applications when conditions in the greenhouse favor disease development.

Bacillus amyloliquefaciens ENV503

(Companion Biological Fungicide Wettable PowderOG) REI 4h, Group BM02

Fungal and bacterial leaf spots, powdery mildew, damping off.  Vegetable transplants in the greenhouse.  Preventive biological fungicide/bactericide for control and suppression of soil and foliar diseases. Activates ISR (induced sytemic resistance). 

Bacillus amyloliquefaciens F727 (StargusOG)

REI 4h,  Group BM02

Bacterial and fungal leaf spot & blights, botrytis blight, late blight, damping off and root rots, downy mildew (depending upon crops, see label).  Bulb, cucurbit, fruiting and leafy vegetable transplants. Broad-spectrum preventive biological fungicide/bactericide for growing media or foliar applications. Activates ISR (induced systemic resistance). 

Bacillus subtilis QST 713
(CEASE OG)  REI 4h, Group BM02 

Fungal and bacterial leaf spots, powdery mildew, Botrytis blight, downy mildew (depending upon crop, see labels).  Cole crops, bulb, cucurbits, leafy and fruiting vegetable transplants. Broad-spectrum, preventative biological fungicide/bactericide. Begin applications when conditions in the greenhouse favor disease development. 

basic copper sulfate 

(Cuprofix Ultra 40 Disperss, Cuproxat, Cuproxat FlOG  ) REI 24/48 h, Group MO1

Leaf spots and blights, downy mildew, bacterial blight, late blight on tomatoes, bacterial spot (depending upon crop, see labels).  Cucumber, eggplant, pepper and tomato transplants.  Preventive, contact fungicides. Crops grown in the greenhouse may be more sensitive to copper injury so the user should determine plant sensitivity. Observe for 7 to 10 days for symptoms of injury. 

boscalid & pyraclostrobin

(Pageant Intrinsic), REI 12h, Group 7 & 11

Leaf spots and blights, powdery mildew, crown and basal rots, damping off, downy mildew, and botrytis blight.  Specified vegetable transplants for the home consumer market: cucurbit, fruiting and leafy greens vegetable transplants.  Preventive, broad-spectrum fungicides. Pyraclostrobin has local systemic activity and translaminar activity. Do not use in agricultural production fields. 

Coniothyrium minitans

(ContansOG), REI 4h, Group BM2

Sclerotinia sclerotiorum and Sclerlotinia minor Brassica leafy greens, bulb vegetables, cucurbit vegetables, fruiting vegetables (except cucurbits), herbs and spices, leafy vegetables, foliage of legume vegetables, legume vegetables (succulent & dried), non-grass animal feeds, ornamental bulbs, ornamental herbaceous potted flowers and bedding plants, leaves of root and tuber vegetables and root & tuber vegetables. Bayer label for Contans does not include tomatoes.

copper hydroxide (KalmorOG), (Kocide 2000-OOG ) REI 24/48h,  Group M01

 

Leaf spots, anthracnose, bacterial spots, late blight and other diseases (see labels). See labels for specific vegetable crops. Protectant, contact bactericides/fungicides. See labels for plant safety information. 
copper octanoate (Camelot OOG), GrottoOG), REI 4h, Group MO1 Bacterial and fungal leaf spots, powdery mildew, downy mildew, early blight, late blight and others (depending upon crop, see labels).  Cole crops, curcurbit, lettuce, onion, tomato, eggplant, and pepper transplants.  Contact bactericides/fungicides. See labels for specific usage instructions and plant safety information. 

copper oxychloride & copper hydroxide

(Badge X2OG),  (Badge SC) REI 24h, Group M01

Bacterial & fungal leaf spots and blights (depending upon crop, see labels). Cucumber, eggplant, pepper,  and tomato transplants.  Contact bactericides/fungicides. Badge X2 is a low load dry copper formulation that is a mixture of two high purity copper salts (copper oxychloride and copper hydroxide). Badge SC is a liquid formulation. See labels for plant safety information. 

copper octanoate 
(Camelot OOG), (GrottoOG), REI 4h, Group M01

Bacterial and fungal leaf spots (many), powdery mildew, downy mildew, early blight, late blight and others (depending upon crop). Cole crops,  cucurbit, lettuce, onion, tomato, eggplant, pepper transplants. Contact bactericides/fungicides. See label for specific usage instructions and plant safety information.

copper sulfate pentahydrate
(Phyton 35), REI 48/24 h, Group M01

Fungal and bacterial leaf spots (see label for specific types and crops), downy mildews, powdery mildews, Botrytis blight, late blight on tomato. Cole crops, cucurbits, eggplant, pepper, and tomato transplants. Systemic, preventative, and curative bactericide/fungicide. Thorough coverage needed. See label for plant safety information. 

cyazofamid 

(Ranman 400SC), (Segway O)

REI 12h, Group 21

Ranman 400SC: Pythium damping off on tomato, downy mildew on herbs in the greenhouse.  Segway O: Pythium damping off on tomato and pepper transplants, Phytophthora blight, crown and root rots on pepper transplants, downy mildew on herbs.

Ranman 400SC: Basil and tomato transplants. Segway O: tomato and pepper transplants.

Locally systemic fungicides. Apply as a drench.
difenoconazole & pydiflumetofen  (Postiva) REI 12h, Group 3 and 7 

Curcurbit vegetables: various leaf spots and blights, powdery mildew 

Tomatoes: Early blight, powdery mildew, Septoria leaf spot 

Specified for cucurbit and fruiting vegetable transplants for retail sale to consumers, not for commericial vegetable production.  Broad spectrum, preventive and systemic fungicide. 

fenhexamid
(Decree 50 WDG), REI 12h, Group 17

Botrytis blight. Tomatoes, cucumber, leafy greens (except spinach) transplants.  Preventative, translaminar fungicide. Do not apply in vegetable agricultural fields.

fludioxonil
(Spirato GHN), REI 12h, Group 12

 

Leaf spots and blights, powdery mildew, botrytis blight (depending upon crop, see label).  Curcurbit, Cole leafy, leafy and fruiting vegetable transplants. Protectant fungicide for certain vegetable transplants. Not for field vegetable production use. 

Gliocladium catenulatum  J1446
(LALSTOP G46 WGOG), REI 4h, Group BM02

 

Damping off, root and stem rot (Alternaria, Fusarium, Pythium, Phytophthora, Rhizoctonia).  Cucurbit, fruiting, leafy, bulb and brassica leafy vegetable transplants.  Preventative biological fungicide that can be incorporated into the media, applied as a drench or foliar spray.
Gliocladium virens GL-21 (SoilGardOG), REI 4h,  Group BM02 Damping off (Pythium, Rhizoctonia, Phytophthora and Fusarium).  Fruiting and leafy vegetable transplants.  Preventive biological fungicide applied before transplanting into the field. 

hydrogen peroxide
(ZeroTol 2.0OG) , REI 1h (spray)

Botrytis, downy mildew, powdery mildew, some leaf spots and blights, and  root rots (see label). Cucurbit, fruiting and leafy vegetables transplants.  Contact fungicide. Strong oxidizing agent. See label for plant safety information. 
hydrogen peroxide & hydrogen dioxide (PERPose PlusOG), REI 1/0 h  Bacterial leaf spot, powdery mildew, downy mildew, Botrytis blight.  Vegetable crops in greenhouses  Works by contact. Strong oxidizing agent. Do not apply in dry, extremely hot conditions. Do not combine with any other pesticide or fertilizer. 

insecticidal soap

potassium salts of fatty acids

(Kopa Insecticidal SoapOG) (M-PedeOG), REI 12h

Powdery mildew.  Cucurbit, fruiting and leafy vegetable transplants and others (see labels).  Contact fungicides. Short residual activity. See labels for plant safety information. 

mancozeb

(Protect DF), REI 24h, Group MO3

Anthracnose, fungal leaf spots and blights, downy mildew, late blight (depending upon crop, see label). Cucumber, melon, squash and tomato transplants. Contact, protectant fungicide. Not for field vegetable production. 
mandipropamid
(Micora), REI 4h, Group 40
Downy mildew, Phytophthora blight (suppression), downy mildew on basil, late blight on tomato (depending upon crop, see label). Basil, leafy and vegetable transplants grown in enclosed greenhouse, with permanent flooring for resale to consumers.  Contact, protectant and translaminar fungicide for listed vegetable and basil transplants for sale to consumers.  

mefenoxam

(Subdue Maxx), REI 0/48h, Group 4

Damping off (Pythium spp.), Crown Rot (Phytophthora spp.,) and downy mildew on Cole crops (depending upon crop, see label).  Cole crops, bulb, curcurbits, fruiting  and leafy vegetables  transplants grown for retail sale to consumers.  Systemic fungicide for listed vegetable transplants grown for retail sale to consumers.

mineral oil 

(SuffOil XOG), REI 4h 

Powdery mildew.  Cucumber, eggplant, melon, pepper, pumpkin, squash and tomato transplants.  Contact fungicide. See label for plant safety information.

pentachloronitrobenzene (PCNB)
(Terraclor 400)
REI 12h, Group 14

Root and stem rot, damping off (Rhizoctonia solani, Pellicularia filamentosa). Limited to vegetable bedding plants: broccoli, Brussels sprouts, cabbage, cauliflower, pepper and tomato.

Protectant, contact fungicide. Apply as a soil drench.

penthiopyrad
(Fontelis), REI 12h, Group 7

Alternaria, Botrytis blight, powdery mildew and various leaf spots and blights (depending upon crop, see label). Tomatoes, peppers, cucurbits.  Broad-spectrum fungicide with preventative, curative and locally systemic activity. See label for plant safety information.

phosphorous acid

(Fosphite) REI 4h, Group P07

Anthracnose, bacterial leaf spot, downy mildew, powdery mildew, root rots (Phytophthora, Pythium, Fusarium, Rhizoctonia).  Brassica, cucurbit, and leafy vegetable transplants.  Systemic fungicide. See label for plant safety information.

phosphorous acid

(Kphite 7LP), REI 4h, Group PO7

Anthracnose, downy mildew, powdery mildew, bacterial leaf spots, root rots (Phytophthora, Pythium, Rhizoctonia, and Fusarium).  Brassica, cucurbit, and miscellaneous food crops.  Systemic fungicide/bactericide. See label for plant safety information. 
phosphorous acid & hydrogen peroxide (OxiPhos), REI 4h  Downy mildew, powdery mildew, black rot (Cole crops), fungal and bacterial leaf spots & blights (depending upon crops, see label).  Bulb, Cole, cucurbit, fruiting and leafy vegetable transplants.  Strong oxidizing agent. Do not use at higher than labeled rates as leaf burn may result. 

polyoxin D zinc salt
(Affirm WDG), REI 4h, Group 19

Cucurbit vegetables: Powdery mildew, Botrytis, Corynespora leaf spot, early blight.

Fruiting vegetables: Powdery mildew, Botrytis, early blight, suppression of anthracnose.

Cucurbit vegetables, fruiting vegetables (eggplant, pepper, tomato) transplants.  Preventative and curative fungicide. Active ingredient (polyoxin) is a natural antibiotic and fermentation product of a soil bacterium. Not for agricultural field use. 

potassium bicarbonate
(Milstop SP OG) REI 1h
(KaligreenOG) REI 4h

Powdery mildew and others (see labels for more information).

Broccoli, Brussels sprouts, cabbage, cantaloupe, caulilfower, celery, cucumber, eggplant, lettuce, onion, okra, pepper, tomato and squash transplants.  (see labels).  Contact foliar fungicides with eradicant activity. Thorough coverage essential. Potassium bicarbonate disrupts the potassium ion balance in the fungus cell, causing the cell walls to collapse.

propamocarb hydrochloride HCl
(Previcur Flex) REI 12h, Group 28

Root rot and damping off (Pythium, Phytophthora). Tomatoes, cucurbits, peppers, greenhouse leaf lettuce. Systemic fungicide. Apply in the evening. Phytotoxicity may occur if applied directly to dry growing media, especially in intense sunlight.
Pseudomonas chlororaphis AF5009 (Zio) REI 4h, Group BM02 Pythium, Phytophthora, Rhizoctona, Botrytis Blight (suppression).  Vegetable transplants such as beans, celery, lettuce, onion, spinach,  crucifer crops, cucurbits and fruiting vegetables.  Preventative biological fungicide. 

pyrimethanil
(Scala SC) REI 12h, Group 9

Gray mold (Botrytis), early blight (Alternaria). Tomato transplants.  Preventative fungicide. Apply only in well-ventilated greenhouses and ventilate for at least 2 hours after application. Phytotoxicity may occur in unventilated greenhouses with relative humidity above 80%.

Reynoutria sachalinensis extract
(Regalia GCOG) REI 4h, Group P05

Powdery mildew, downy mildew, bacterial leaf spot, early & late blight, Alternaria leaf spot, botrytis blight, damping off (Pythium, Rhizoctonia, Fusarium, Phytophthora)  (depending upon crop, see label). Bulb, Cole crops,  cucurbit, fruiting, leafy Cole and leafy vegetable transplants.  Preventive, biological fungicide with translaminar activity.  Plant activator. Formulation of an extract from giant knotweed. Use preventatively to increase the natural defense system of plants.

Streptomyces  K 61 (MycostopOG), REI 4h, Group BM02

Alternaria, Botrytis blight (suppression),  damping off and root rots (Fusarium, Phytophtora, Pythium, Rhizoctonia).

Many vegetable transplants. Do not treat melon seeds.  Preventative biological fungicide. Contains a beneficial bacterium. Repeat applications may be needed. Apply as a soil spray or drench.

Streptomyces lydicus  WYEC 108 (Actinovate AGOG)  REI 1h

Suppression of  root rots (Fusarium, Rhizoctonia, Pythium, Phytophthora), and foliar diseases (downy mildew, powdery mildew, Botrytis, Alternaria). Cole crop, bulb, cucurbit, fruiting and leafy vegetable transplants.  Preventative biological fungicide for suppression of root rot diseases and foliar pathogens. 

streptomycin sulfate
(Agri-mycin 50) REI 12h, Group 25

Bacterial spot and speck. Tomatoes and pepper transplants. Xylem mobile fungicide. Repeated applications can result in resistant bacteria.

sulfur
(Microthiol DisperssOG)  REI 24h, Group M02

Powdery mildew. Many vegetables (see label).  Contact fungicide. Crops grown in greenhouses may be more sensitive to sulfur injury, so the lowest label rate should be tried initially. Do not use within two weeks of an oil spray treatment.

Swinglea glutinosa extract

(EcoSwing)OG REI 4h, Group BMO1

 Botrytis blight, powdery mildew, Basil downy mildew.   Bulb, Cole crops, cucurbit, fruiting and leafy vegetables.  Preventive biological fungicide. Activates ISR (induced systemic resistance). Thorough coverage is needed. 

thiophanate methyl

(3336 F), (3336 EG),  REI 12h, Group 1 

Anthracnose, botrytis blight, powdery mildew and others depending upon crop, see label.  Cucurbits and bean transplants.  Xylem mobile systemic fungicide. Resistant populations of Botrytis are common in the greenhouse. Not for field vegetable production. 
thyme oil  (Guarda) REI 0h Botrytis, downy mildew, powdery mildew, fungal and bacterial leaf spots and blights, damping off (Pythium, Fusarium, Phytophthora, Rhizoctonia). Bulb, Cole crops, cucurbits, fruiting and leafy vegetables.  Stabilized thyme oil extract. Contact fungicide that disrupts cell membranes with some translaminar activity. Repeated applications needed. 
Trichoderma asperellum (ICC 012) & Trichoderma gamsii (ICC 080)
(Bio-Tam 2.0 OG ), (ObtegoOG) REI 4h, Group BM02
Root rots (Fusarium, Phytophthora, Pythium, Rhizoctonia, and Thielaviopsis). Cucurbit, fruiting and leafy vegetable transplants.  Preventative biological fungicides. 

Trichoderma harzianum  T-22 
(RootShield GranulesOG), REI 4h 

Group BM02

Root rots (Pythium, Rhizoctonia, Fusarium, and Thielaviopsis).

Bulb, cucurbit, fruiting, leafy and brassica leafy vegetable transplants. 
 

Preventative biological fungicide that can be incorporated into greenhouse planting mix.

Trichoderm harzianum T-22

(RootShield WPOG) REI 4h Group BM02

Root rots (Pythium, Rhizoctonia, Fusarium and Thielaviopsis). Brassica leafy vegetables, bulb, cucurbit and fruiting vegetable transplants.  Preventive biological fungicide. Apply as a soil drench only.

Trichoderma harzianum  T-22 &
Trichoderma virens G-41
(RootShield Plus WPOG),
(RootShield Plus GOG) REI 4h

Group BM02

Root rots (Pythium, Phytophthora, Rhizoctonia, Fusarium,  and Thielaviopsis). Bulb, cucurbit, fruiting, leafy and Cole crop leafy vegetable transplants. 
 
Preventative biological fungicide. Apply as a soil drench (RootShield Plus WP) or incorporate into greenhouse planting mix (RootShield Plus Granules). 
Triflumizole (Trionic 4SC), (Terraquard SC), REI 12h, Group 3 Powdery Mildew.  Cucumber and tomato transplants. Protective fungicides with curative action. 

Ulocladium oudemansii  U3

(BotryStopOG ),  REI 4h 

Group BM02

Botrytis blight.  Bulb, cucurbit,leafy, and fruiting vegetable transplants.  Preventive biological fungicide. Thorough coverage needed. 

The symbol OG indicates a pesticide is listed by the Organic Materials Review Institute (OMRI) as approved for use in certified organic production.

This information is supplied with the understanding that no discrimination is intended and no endorsement implied. Due to constantly changing regulations, we assume no liability for suggestions. If any information in these tables is inconsistent with the label, follow the label.

 

Transplant Insect and Mite Management

Monitoring

A regular monitoring program is the basis of pest management. Conduct regular, weekly scouting to detect problems early. 

Yellow Sticky Cards

Use yellow sticky cards to trap and detect adult stages of fungus gnats, thrips and whiteflies. Place one to four cards per 1,000 square feet. The cards should be spaced equally throughout the greenhouse in a grid pattern with additional cards located near doorways and vents. Place some cards just above the plant canopy (to detect thrips and whiteflies) and some of the cards on the rim of the flats or pots to detect fungus gnats. Inspect and replace the cards weekly to keep track of population trends.

Plant Inspection

Plant inspection is needed to assess general plant health and to detect diseases, mites and aphids plus any hot spots of immature whiteflies. Randomly select plants at ten locations in an area of 1,000 square feet, examining plants on each side of the aisle. Start this pattern at a slightly different location each week, walking through the greenhouse in a zigzag pattern down the walkway. Examine the underside of leaves for insect pests and inspect root systems to determine whether they are healthy.

Key Plants and Indicator Plants

Focus on scouting key plants and indicator plants. Key plants are those plants or cultivars that have serious, persistent problems every year. For example, pepper, eggplant and leafy greens are prone to aphid infestations. Look for aphids on the young leaves and for shiny honeydew on the upper leaf surface. If grown near flowering plants, peppers and eggplant will also indicate an early thrips population. Look for distorted, young leaves with silvery flecked scars, signs of thrips feeding damage.

Fava beans and certain cultivars of petunia are used as indicator plants to detect the presence of thrips carrying INSV and TSWV. These plants will develop viral symptoms within one week if fed on by the infected thrips. The petunia cultivar 'Summer Madness' and several varieties of fava bean have been successfully used to detect tospoviruses. To use petunias and fava beans as indicator plants:

  • Remove flowers from indicator plants to encourage feeding on foliage where symptoms can be observed.
  • Place a blue non-sticky card in each pot at plant height. The blue card will attract thrips to the indicator plant. Blue plastic picnic plates work well.
  • Place petunia plants throughout the greenhouse among the crop at a rate of one plant every 20 to 30 feet and fava bean plants at the rate of 12 pots per 1,000 sq. ft.
  • Remove symptomatic leaves on petunia plants and continue to use the plants. The virus is not systemic in these plants. Thrips feeding injury leaves distinct white feeding scars on the foliage. Virus symptoms appear as a brown rim around the feeding scars.
  • Remove entire plants of fava beans if symptoms are observed, because the virus is systemic in these plants. Viral symptoms appear as dark brown angular lesions on leaves or yellow to light green ring spots. Dark necrotic areas can also be seen on the stem. Fava beans have dark black spots on their stipules that should not be confused with viral symptoms.
  • Replace with new plants, planting 1-2 bean seeds per 4" pot.

Record Keeping and Decision-Making

Each time the crop is scouted, record the pest numbers, their location and the number of plants inspected. Records on pest numbers and locations will help you identify population trends. Population trends will also indicate if initial control measures were successful or if they need to be repeated. Once this information is collected each week, a pest management decision can then be made. Monitoring and record keeping will answer the following questions and help you make the necessary treatment decisions. Is the population decreasing, increasing or remaining stable over the growing season? Do you need to spray?  Do you need to release more natural enemies? Are insects migrating from weeds under the benches to your crops? Is the treatment from last week working? See Tables 19 (page 54) and 20 (page 62) for selected materials labeled for managing insects, mites and diseases on greenhouse-grown vegetable transplants. Follow label instructions before using the material on vegetable transplants. The product must be used only for crops for which the compound is registered.

Biological Control for Insects and Mites

Biological control is the use of living organisms (biological control agents) such as insects, predatory mites, fungi or bacteria to manage pests.  They are best used preventively, early in the cropping cycle. Growers often start with the use of insect killing nematodes against fungus gnat larvae,  different predatory mite species for use against thrips and spider mites and host specific parastic wasps against whiteflies. 

Some of the advantages of using biological control agents include:

  • less worker exposure to pesticide residues. 
  • less chance of plant damage from sprays. 
  • improved plant quality.
  • no re-entry intervals (REI) to follow. 

Biological control programs use living organisms, so extra care and effort is needed to make these programs work. Committment, patience, and a desire to learn about the life history and environmental requirements of the pest and it's natural enemy are all needed.  The support of the owner, management and a dedicated staff are all needed. 

A detailed plan of action is needed to insure success. Biological controls are best used with proper cultural controls and sanitation practices. Careful planning is needed to insure success. Start planning 6 months to one year in advance. Develop a spreadsheet of your planting schedule and when your greenhouses will be open for production to help pre-order biological control agents.  Accurately identify the key pests in your production system. Natural enemies, especially parasites, are often very specific to a particular pest. They may also be shipped in a stage that does not attack the targeted pest.  Many insecticide residues can adversely affect natural enemies for up to 3 to 4 months after their application.  Review your pesticide use before starting biological controls.  For more information on the compatibility of pest control materials with natural enemies, refer to online resources, such as:

1) Koppert's online interactive database: www.koppert.com

2) Biobest: http://www.biobestgroup.com/ (click on "side effect manuals")

3) BASF (formerly Becker Underwood), Nemasys chemical compatibility guide:https://betterplants.basf.us/content/dam/cxm/agriculture/better-plants/united-states/english/products/nemasys-beneficial-nematodes/nemasys-chemical-compatibility-guide.pdf

4) BioWorks Botanigard biocompatibility:

5) Bioline Agrosciences 

Start in a small trial area to become familiar with releasing, monitoring and evaluating the effectiveness of natural enemies. With help from your supplier and University specialist, establish a schedule for introducing the natural enemies. Release rates and timing will vary depending upon the crop and its size, the degree of infestation, effectiveness and type of natural enemies, plus the time of year. Vegetable transplants with only one or two key insect pests or with a longer production schedule may be logical candidates for biological control.  Some growers have started with using biological controls against fungus gnats (beneficial nematodes) and thrips (predatory mites), especially if long term crops are in the same greenhouse. Be sure that natural enemies are received from your supplier quickly (within 4 days), and that they are kept cool during shipment.  The predatory mites, Phytoseiulus persimilis that are used against two spotted spider mites, that are often shipped without a food source, should be received after an overnight delivery. 

Inspect natural enemies for viability and quality when they are received. Biological control suppliers often send a description of what to look for when receiving the natural enemies.  The package containing biological control agents should be shipped in a sturdy container, such as a polystyrene box that minimizes exposure to high and low temperatures.  When you receive the natural enemies, check the temperature within the shipping box with an infrared thermometer. A moldy odor or condensation is of concern.  Most natural enemies should be released immediately upon arrival.  For more specific information, see Grower Guide: Quality Assurance of Biocontrol Products compiled by Dr. R. Buitenhuis at: https://www.vinelandresearch.com/wp-content/uploads/2020/02/Grower-Guide.pdf

In order for a biological control program to be successful, it is critical to establish a good working relationship with your supplier or distributor of biological control agents.  Ask them if they provide technicial support or consulting services and what their delivery schedule and shipping costs will be.   Here is a partial list of some of the biological control suppliers or distributors of biological control agents used by New England greenhouse growers. 

See Table 18 (page 51) for information on scouting for key pests and biological control options and Table 20 (page 62) for insecticides labeled for vegetable transplants.

Aphids

Lifecycle: Several species of aphids can occur on vegetable transplants, but the most common are green peach, melon, foxglove and potato. Aphids are small, 1/16" in length, round, soft-bodied insects that vary in color from light-green to pink or black. The green peach aphid is yellowish-green in summer; pink or yellowish in fall and spring. Winged forms are brown with a large dusky blotch on the abdomen. Melon aphids are greenish-yellow to very dark green with black mottling and short dark cornicles or "tailpipes" (tubular structures on the posterior part of the abdomen). Foxglove aphids are smaller than potato aphids but larger than melon and green peach aphids. The foxglove aphid is a shiny light yellowish green to dark green in color with a pear-shaped body. The only markings on the bodies of wingless adults are dark green patches at the base of the cornicles. The legs and antennae also have black markings. Foxglove aphids cause more leaf distortion than green peach or melon aphids. Potato aphids have antennae longer than their bodies with long cylindrical tailpipes and are green or pink.

Aphids feed by inserting their piercing, sucking mouthparts into plant tissue and removing fluids. In greenhouses, aphids are usually females that produce live young called nymphs. Each female can produce 50 or more nymphs. Nymphs mature to adulthood and begin reproducing in as little as 7-10 days. Adults are usually wingless, but some will produce wings when populations reach outbreak levels. Large numbers of aphids will stunt and deform plants. In addition, aphids produce a sticky digestive by-product called honeydew and their white shed cast skins may be unsightly. Sometimes, these white cast skins are mistakenly identified as whiteflies. Honeydew can cover leaves and provide a food source for a superficial black fungus known as "sooty mold." Aphids are present on weeds and winged aphids may also enter the greenhouse through vents. Aphids can also transmit certain viruses.

Monitoring: Examine the foliage, along stems and new growth of key plants such as pepper, eggplant, cole crops and leafy greens to detect an early aphid infestation. Signs of aphid activity include shed white skins, shiny honeydew, curled new leaves, distorted growth and the presence of ants. Yellow sticky cards help detect the entrance of winged aphids into the greenhouse from outdoors. Yellow cards will not, however, allow you to monitor aphids within the crop, as most of the aphids will be wingless.

Caterpillars

Lifecycle: Caterpillars are the immature or larval stage of moths and butterflies (Lepidoptera).  Most overwinter outdoors and may migrate into greenhouses especially during the summer and fall.  Although they are not major pests of greenhouse crops, night flying moths may be attracted to lights near greenhouses.  Female moths enter the greenhouse to lay their eggs on susceptible crops. Their life cycle consists of egg, larvae, pupa and adult.   Females emit pheromones that attract males, and after mating, the females lay eggs that hatch into rapidly growing caterpillars. They may molt up to 3-5 times before entering a resting stage.  Day flying butterflies, such as the imported cabbageworm, develop into a chrysalis as a resting stage and night flying moths develop into a pupal cocoon. Depending upon the species there may be from 1 to 3 or 4 generations a year.  Cole crops are especially susceptible to damage from the imported cabbageworm, cabbage looper, diamondback moth and cross-striped cabbageworm.

Monitoring: Visually inspect plants when adults are active. In greenhouses, pay close attention to plants near doors, vents and other openings, especially near weedy areas or near vegetable fields.

Fungus Gnats, Shore Flies, and Predatory or Beneficial Hunter Flies

Lifecycle: The damp, moist environment in greenhouses favors both fungus gnats and shore flies. Fungus gnat larvae are translucent, white and legless, about 1/4" long when mature, and have a shiny black head. The mosquito-like adult is about 1/8" long with long legs, a pair of clear wings and long antennae. There is a distinct "Y" vein on each wing. Fungus gnats are weak fliers and are frequently observed resting on potting media or running over the foliage or other surfaces. The larvae feed on fungi and decaying organic matter, and often injure seedlings and plants. Larva feeding occurs on young, tender roots and in the stem at the base of the plant. This feeding injury provides an entry for disease pathogens. A female fungus gnat may lay up to 300 whitish eggs in clusters of 20 or more. The eggs are deposited on the surface or in the crevices of moist soil or potting media. Eggs hatch in about six days. Larvae feed for 12-14 days before changing into pupae. The pupal stage may last 5-6 days. Adults live up to ten days. The life cycle from egg to adult requires approximately 21-28 days depending on greenhouse temperatures.

Adult shore flies also occur in damp greenhouses. Shore flies are often misidentified as fungus gnats or hunter flies but they have a distinctly different appearance. The adult shore fly is about 1/8" long and has a robust body, very short antennae, shorter legs and dark wings with about five light spots. Adults may be seen resting on plant leaves. Larvae are off-white and do not have distinct head capsules that are characteristic of fungus gnat larvae. Shore flies do not injure plants through direct feeding, but can carry root rot pathogens from diseased to healthy plants. Their fecal spots or droppings can also be unsightly. To manage shore flies, control their food source, algae.

Adult hunter flies, a natural enemy (beneficial fly) are also found on sticky cards that may be mistaken for shore flies. Hunter flies can be distinguished from shore flies, by their size and color. Hunter flies are about twice as large as shore flies with wings that are uniformly clear and do not have light spots on their wings. Hunter flies are in the same family as common houseflies and are similar in appearance. Hunter flies may prey upon fungus gnats and shore flies.

Monitoring: To monitor for fungus gnat larvae, place raw potato chunks (with peel removed) on the soil surface. Larvae are attracted to the potato chunks and will congregate underneath. Check the potato chunks after 2 days for the larvae. Potato disks cut one inch in diameter and 0.5"-1" thick are effective. In addition, choose plants on each bench and inspect the soil surface and around the base of the plant including the stem just below the soil line. Record the location and the level of infestation. Badly infested plants should be removed as they serve as a source of infestation.

Adult fungus gnats can be monitored with yellow sticky cards placed at the base of the plant at the soil line. Weekly inspections of yellow sticky cards can detect the onset of an infestation, and continued recording of the number of adults per card per week can aid in evaluating the efficacy of control efforts.

Leafminers

Spinach leafminer (Pegomya hyoscyami Panzer) and beet leafminer (Pegomya betae) feed between the upper and lower epidermis of the leaf. Early damage is a slender, winding ‘mine’ or tunnel, but as the larva feeds and grows these may expand and become blotches on the leaves.  Spinach and beet leafminers may cause damage on chard, beet, and spinach transplants.

Life Cycle: Adult spinach and beet leafminers are flies that overwinter as pupae in the soil and emerge in late-April and May. The two species are similar in behavior, appearance, plant hosts, and damage, but beet leafminer adults are slightly larger and darker, and beet leafminers prefer laying eggs on beet leaves. The small, gray adult flies lay small, oblong white eggs in clusters on the undersides of leaves. Eggs develop into pale, white maggots that damage the leaves. The larva burrows between the upper and lower epidermis of the leaf and feeds, creating a slender, winding ‘mine’ or tunnel. This expands into large blotches of translucent, dead tissue across the leaf, with a white maggot inside.  When fully grown, maggots usually drop into the soil to pupate, though they may also pupate inside the leaf. The entire life cycle is 30-40 days and there are three to four generations per season.

Monitoring: Look for the small, oblong, white eggs that are laid in neat clusters on the underside of the leaves.  Inside the mines look for one or several pale, white maggots.

Mites

Two-spotted Spider Mites

Lifecycle: Two-spotted spider mites can be found on vegetable transplants. Adult females are approximately 1/50" long, and slightly orange in color. All mobile stages are able to pierce plant tissue with their mouthparts and remove plant fluids. Most spider mites are found on the underside of leaves. Feeding injury often gives the top leaf surfaces a mottled or speckled, dull appearance. Leaves then turn yellow and drop. Large populations produce visible webbing that can completely cover the leaves. Eggs are laid singly, up to 100 per female, during her 3-4 week life span. Eggs hatch into larvae in as few as 3 days. Following a brief larval stage, several nymphal stages occur before adults appear. Egg to adult cycle can be completed in 7-14 days depending upon temperature. Hot and dry conditions (80oF and 30-50% RH) favor spider mite development.

Monitoring: Check for mites by examining foliage. Adult spider mites are not found on sticky cards. Mites often develop as localized infestations on bean, tomato, or eggplant. Sample plants by turning over leaves and with a hands-free magnifier (Optivisor™) or hand lens, check for the presence of spider mites.

Broad Mites

Life Cycle: Broad mites are closely related to cyclamen mites. They can be distinguished from cyclamen mites by their egg stage. Eggs are covered with "bumps" that look like a row of diamonds. Eggs are best seen using a dissecting microscope. Adults and larvae are smaller than the cyclamen mites and walk rapidly on the underside of leaves. Broad mites can also attach themselves to whiteflies and use the whiteflies as a carrier for their dispersal. The development of broad mites is favored by high temperatures (70o-80F and 80%-90% RH). Broad mites can complete their life cycle in as little as one week. Females lay from 30 to 75 eggs.

Monitoring: Broad mites can affect a number of ornamentals including gerbera daisy, New Guinea impatiens, salvia, ivy, verbena and zinnia. They may migrate to pepper or tomato. Look for characteristic damage including leaf edges curling downward. Terminal buds may be killed. As they feed, broad mites inject toxic saliva, which results in the characteristic twisted, distorted growth. Broad mite injury can be mistaken for herbicide injury, nutritional (boron or calcium) deficiencies or physiological disorders. Inspect the underside of the leaves for the mites and their eggs with a 20x hand lens or submit samples to a laboratory for diagnosis. Microscopic examination is often needed.

Cyclamen Mites

Life Cycle: The shiny, orange-tinted cyclamen mites prefer to hide in buds or deep within the flowers. Eggs are deposited in moist places at the base of the plant. Cyclamen mites can complete their life cycle in 1-3 weeks. Females can live up to one month and can reproduce without mating. Cyclamen mite females lay 2-3 eggs per day for up to 2-3 weeks. Cyclamen mite eggs are oval, smooth and about one half the size of the adult female. Larvae hatch from the eggs in 3-7 days. The slow moving white larvae feed for 4-7 days. Cyclamen mites prefer high relative humidity (80%-90% RH) and temperatures of 60º F. Cyclamen mites affect a number of ornamental bedding plants including dahlia, fuchsia, gerbera daisy, petunias and viola. They may migrate to peppers or tomatoes.

Monitoring: Cyclamen mites pierce tissue with their mouthparts and suck out cell contents. Look for signs of damage which may be concentrated near the buds or occur on the entire plant. Symptoms include inward curling of the leaves, puckering and crinkling. Pit-like depressions may develop. The mite is only 1/100th of an inch long. Examination under a microscope is often needed to confirm the presence of cyclamen mites.

Slugs

Life Cycle: Slugs are classified as mollusks and are covered with mucous-like slime that protects their bodies from desiccation. Slugs lay translucent pearl-shaped eggs in clusters of 20-100 in cool, moist locations such as in the soil or growing medium or underneath containers. Eggs hatch in less than 10 days at 50ºF. Young slugs resemble adults but are lighter in color and smaller. They mature in 3-12 months and adults may live a year or more. Slugs contain both male and female organs and may alternate sexes at different times during adulthood.

Monitoring: Slugs vary in size from 3/4 to 1-1/2 inches in length. Their color ranges from pale yellow to lavender or purple. Slugs feed on a wide-range of greenhouse grown crops at night. They use their chewing mouthparts to create holes in leaves and stems. Feeding damage from slugs may be confused with caterpillars. However, slugs completely consume leaves and stems, whereas caterpillars may leave portions of stems or leaf veins. Slugs also leave shiny mucous-like slime trails.

Thrips

Lifecycle: The most injurious species is the western flower thrips (WFT). They often do considerable damage before they are discovered because thrips are small, multiply rapidly and feed in plant buds in which they can remain undetected. WFT also vector tospoviruses. Feeding marks from the rasping mouthparts of thrips appear as white streaks on the leaves. Infested new growth may curl under and leaves are often deformed. Adult WFT are about 1/16" long, with narrow bodies and fringed wings. Females are reddish brown and males are light tan to yellow. The wingless immature larval stages are light yellow. Female thrips insert eggs (several hundred per female) into plant tissue. The tiny yellowish larvae molt twice and feed on plant fluids as they mature. Larvae fall off the leaves and drop into the growing media, passing through two stages, after which adults emerge. The egg to adult lifecycle can be completed in 2-4 weeks depending upon greenhouse temperature. During warmer temperatures development is more rapid than at cooler temperatures.

Monitoring: Early detection of a thrips infestation is critical for effective management because populations are lower and it is easier to obtain good spray coverage when plant canopies are small. Symptoms of their feeding are often not noticed until the damage has occurred. Eggplant, tomato, pepper and leafy greens are prone to thrips infestations. Yellow sticky cards, key plants and indicator plants can be used to detect the onset of an infestation. Yellow sticky cards should be placed just above the crop canopy, and near doors, vents and over thrips-sensitive cultivars to monitor their movement. The light to medium-blue sticky cards may catch more thrips (and shore flies) than yellow ones. However, it is more practical to use yellow cards for general pest monitoring to attract fungus gnats, whiteflies and winged aphids. The number of thrips per card should be recorded and graphed weekly to monitor population levels and movement in or out of the greenhouse. See section on key plants and indicator plants (page 58) for more monitoring information.

Whiteflies

Lifecycle: The sweet potato (a.k.a. silverleaf) whitefly B biotype (Bemisia argentifolii) and greenhouse whitefly (Trialeurodes vaporariorum) may infest vegetable transplants. However, greenhouse whitefly is the most common species in New England. Both adult and immature whiteflies have piercing sucking mouthparts to remove fluids. Like aphids, they also produce honeydew that results in sooty mold fungus. Winged adult whiteflies are 1/16" in length, and are usually found on the youngest, most tender leaves. Females may lay from 150-300 eggs, which hatch into first-instar nymphs in about a week. These “crawlers” move for a short distance before settling down to feed. After three molts, a pupal stage is formed, and adults emerge in about six days. Whiteflies complete their egg to adult cycle in 21-36 days, depending upon greenhouse temperatures.

Monitoring: To monitor whiteflies, check susceptible plants, such as tomato, at ten locations in an area of 1,000 square feet, examining plants on each side of the aisle. Look on the undersides of one or two leaves per plant, for nymphs, pupa and adults. Yellow sticky traps can also be used to detect adult whiteflies once populations have reached higher densities. Begin treatments as soon as the first sign of infestation is noted.

Table 20: Insecticides Labeled for Insects and Mites on Vegetable Transplants

Insecticide Target Pests Labeled Crops Comments

acetamiprid
(Tristar 8.5 SL) REI 12h, Group 4A

Aphids, beetles, caterpillars, fungus gnat larvae, leafminers, leafhoppers, plant bugs, thrips, whiteflies.

Bulb, Cole, cucurbit, fruiting and leafy greens vegetable transplants. 

Contact insecticide with high absorption and upward systemic mobility. 

afidopyropen (Ventigra) REI 12h, Group 9D Aphids, whiteflies, mealybugs.  Cole, cucurbit, fruiting and leafy vegetable transplants for the home consumer market.  Contact insecticide with ingestion and translaminar activity. For vegetable transplants sold for consumer market only, not for commercial agriculture production in field. 

azadirachtin 
(Aza-DirectOG), (AzaGuardOG), (Azatin OOG), Molt XOG), (Neemix 4.5OG) REI 4h; (Ornazin 3% EC) REI 12 h

Aphids, beetles, caterpillars, thrips, fungus gnat larvae, leafminers, whiteflies and other insects (depending upon labels).  Many vegetables (see specific labels). Contact insecticide. Insect growth regulator for immature stages of insects. Repeat applications are needed.
azadirachtin & pyrethrins
(Azera ProOG) REI 12h, Group unknown & 3A
Aphids, beetles, caterpillars, fungus gnats, leafhoppers, leafminers, shore flies, thrips, whiteflies. Bulb, leafy, Brassica leafy, fruiting and cucurbit transplants.  Insect growth regulator and contact insecticide combined.

Bacillus thuringiensis subsp. aizawai (Agree WGOG) REI 4h, Group 11A

Certain caterpillars (see label). Many vegetables (see label). Stomach poison that must be ingested to be active. Most effective against small, newly hatched larvae. Insects stop feeding and die 1 to 5 days later. Thorough spray coverage needed.

Bacillus thuringiensis subsp. kurstaki (BT NowOG), (DiPel Pro DFOG) (Javelin WGOG)  REI 4h, Group 11A

Certain caterpillars (see labels). Many vegetables (see labels). Stomach poison that must be ingested to be active. Thorough coverage of all plant parts is important. Most effective against small, newly hatched larvae. Insects stop feeding and die 1 to 5 days later. 

Bacillus thuringiensis subsp. israelensis (Gnatrol WDGOG) REI 4h, Group 11A

Fungus gnat larvae. Leafy and Cole crops, cucumber, pepper, tomatoes and eggplant transplants.  Stomach poison that must be ingested to be active. Most effective against first instar larvae. Apply as soil drench. Larvae must ingest material to be killed. 
Beauveria bassiana ANT-03 (BioCeres WPOG) REI 4 h Aphids, plant bugs, thrips, whiteflies and others (see label).  Brassica leafy, bulb, cucurbit, fruiting and leafy vegetables.  Contact insecticide. Active ingredient is a insect-killing fungus. 

Beauveria bassiana GHA
(BotaniGard ES), (BotaniGard 22WP) 
(Mycotrol WPO, ESOOG) REI 4h

Aphids, thrips, whiteflies (See labels for more information). Many vegetables. Do not use ES formulation on tomato transplants. Contact insecticides. Active ingredient is an insect killing fungus. Treat when insect populations are low. Repeated applications may be needed.
Beauveria bassiana PPRI 5339 (Velifer), REI 12h Aphids, mites, thrips, whiteflies.  Vegetable transplants for the home consumer market.  Contact insecticide.  Active ingredient is an insect killing fungus. Treat when populations are low.  Repeated applications may be needed. 
Burkholderia A396
(Venerate GCOG) REI 4h
Aphids (suppression),  caterpillars, mites, thrips, whiteflies.   Bulb, Cole crops, cucurbits, leafy and fruiting vegetable transplants.  Contact insecticide and stomach poison that disrupts insect exoskeleton interfering with molting.

canola oil & pyrethrins

(Pycana)OG REI 12

Aphids, beetles, caterpillars, fungus gnats, leafhoppers, leafminers, plant bugs, spider mites,  thrips, whiteflies.  Bulb, leafy, fruiting, cucurbit, Brassica leafy vegetable transplants.  Combination of a botanical oil and pyrethrins. See label for plant safety information. 

chlorfenapyr
(Pylon) REI 12h, Group 13

Caterpillars (including hornworms), broad mites, two-spotted spider mites, thrips. Tomato, tomatillo, ground cherry, peppers, eggplant. Do not use on tomato varieties with a diameter of less than one inch when mature. Insecticide/miticide with contact and translaminar activity. Active on larvae and nymphs of two-spotted spider mites and thrips. 

chlorfenapyr
(Pylon TR) REI 12h, Group 13

Caterpillars, broad mites,  two- spotted spider mites, thrips (suppression).  Greenhouse fruiting vegetables such as eggplant, pepper and tomato.  Contact insecticide/miticide with translaminar and stomach poison activity.
Chromobacterium subtsugae PRAA4-1 (Grandevo GC OG) REI 4h Aphids, beetles, caterpillars, leafhoppers, plant bugs, mites, thrips, whiteflies (depending upon crop, see label). Brassica leafy, bulb, cucurbit, fruiting and leafy vegetable transplants.  Contact biological insecticide for young immature stages.  See label for plant safety information. 
cyflumetofen (Sultan) REI 12h, Group 25 Two-spotted spider mites.  For specified cucumber and fruiting vegetable transplants for the home consumer market.  Contact miticide.  Do not use for vegetable transplants for agricultural field production. 
cyromazine
(Citation) REI 12h, Group 17
Dipterous leafminers (Liriomyza species), fungus gnat and  shore fly larvae. Vegetable transplants grown for consumer use (see label for specific types). Insect growth regulator. Applied to growing medium to control fungus gnat and shore fly larvae. Available in water-soluble packets.

dinotefuran
(Safari 20 SG) REI 12h, Group 4A

Aphids, leafminers, thrips (suppression), whiteflies. Cucurbit, Cole crop, fruiting and leafy vegetable transplants grown in enclosed structures. Contact and systemic insecticide for foliar application. 

flupyradifurone

(Altus) REI 4h, Group 4D

Aphids, leafhoppers, whiteflies. 

 

Cucumber, lettuce, pepper and tomato transplants. 

Systemic insecticide with translaminar activity. See label for precautions on cucumbers. Do not make more than 1 application per crop prior to transplant.  Do not rotate with Group 4A products.

hexythiazox
(Hexygon IQ) REI 12h, Group 10A
Two-spotted spider mites. Pepper, eggplant, and tomato transplants. Ovicide (egg-killing) activity. Most active on eggs and immature (larvae and nymphs) stages.  Use only once per calendar year. 

imidacloprid
(Marathon II) REI 12h, Group 4A

Aphids, fungus gnat larvae, leafhoppers, leafminers, thrips (suppression), whiteflies. Vegetable bedding plants intended for resale only (See labels for specific types). Contact, systemic and translaminar insecticide. Do not rotate with other products in Group 4A. 

insecticidal soap potassium salts of fatty acids 

(Kopa Insecticidal SoapOG) REI 12 h 

Aphids, mites, plant bugs, whiteflies.  Bulb, Cole crop, cucurbit, fruiting, leafy and other vegetable transplants.  Contact insecticide/miticide. Short residual activity. See label for plant safety information. 

insecticidal soap
Potassium salts of fatty acids
(M-PedeOG), REI 12h

Aphids (suppression),  broad mites, leafminers, leafhoppers, plant bugs, spider mites, thrips, whiteflies. Bulb, Cole, leafy, fruiting and cucurbit vegetable transplants.  Contact insecticide/miticide.  Short residual activity. Refer to label for information on plant safety. Can be tank mixed with other products to increase efficacy.

iron phosphate
(SluggoOG) REI 0h

Slugs and snails. Many vegetables (see label).  Bait. Ingestion causes the slugs and snails to cease feeding, become less mobile and begin to die in 3 to 6 days. Best applied in the evening.  Can be used around pets and wildlife. 

iron phosphate & spinosad

(Brandt Antixx Plus Insect, Slug and Snail BaitOG) REI 4 h

Cutworms, slugs, snails.  Bulb, Cole crop, cucurbit, leafy and fruiting vegetables.  Bait. 

iron phosphate & spinosad
(Bug-N-SluggoOG) REI 4h

Cutworms, slugs, snails. Many vegetables (see label). Bait.  Refer to label for application rates.

Isaria fumosorosea Apoka strain 97
(AncoraOG) (PFR-97 20% WDGOG)  REI 4h
 

Aphids, leafminers (Liriomyza spp.), plant bugs, spider mites, thrips, whiteflies. Drench application to thrips pupae. 

Vegetables grown in greenhouse. Microbial insecticides that work by contact. Apply when relative humidity is >80% with moderate temperatures.   See technical sheet and labels for application directions. 
Isaria fumosorosea FE 9901 (NoFly WPOG  Whiteflies, aphids, thrips, fungus gnats, leafhoppers and others.  Vegetables grown in greenhouse.  Microbial insecticide that work by contact.  Apply when relative humidity is >50% with moderate temperatures.  Repeated applications needed. 
mineral oil (Organic JMS Style OilOG) REI 4h Leafhoppers, leafminers, mites and whiteflies.  Cole crops, cucurbit, fruiting and leafy vegetable transplants.  Contact insecticide/miticide. Foliar injury may occur if applied during humid conditions. See label for plant safety information. 
mineral oil (Suffoil-XOG) REI 4h Aphids, beetle larvae, leafhoppers, leafminers, mites, thrips, whiteflies.  Cucumber, eggplant, melon, pepper, pumpkin, squash and tomato transplants.  Contact insecticide/miticide. Foliar injury may occur if applied during humid conditions.  See label for plant safety information. 
mineral oil (Ultra-Pure OilOG) REI 4 h  Aphids, beetle larvae, leafhoppers, leafminers, mites, thrips and whiteflies.  Many vegetables (see label).  Contact insecticide/miticide.  Foliar injury may occur if applied during humid conditions.  See label for plant safety information. 
neem oil
(Triact 70OG) REI 4h

Aphids, broad mites, leafhoppers, spider mites, thrips (suppression), whiteflies. 

Bulb, Cole crop, cucurbit, fruiting and leafy vegetable transplants.  Contact insecticide/miticide. Thorough coverage of all plant parts is important.  Refer to label for information on plant safety. 
parasitic nematodes (Steinernema carpocapsae) (Millenium) Exempt from REI  Shore fly larvae.  Greenhouse crops. Apply to moist growing media (55˚ to 86˚F) during cloudy, overcast conditions.  Remove screens and filters from sprayers and injectors.  Repeat applications needed in areas where algae is growing.
parasitic nematodes
(Steinernema feltiae)  (NemaShield, Nemasys, Scanmask) Exempt from REI 
Fungus gnat larvae, thrips pupae in growing media.  Greenhouse vegetables.

Apply to moist growing media (50-80˚F) during cloudy, overcast conditions.  Remove screens and filters from sprayers and injectors.  

pymetrozine (Endeavor) REI 12 h, Group 9B Aphids, whiteflies (suppression).  Cole crops, cucurbits, fruiting and leafy vegetables for the home consumer market.  Insecticide with systemic and translaminar activity. For use on listed vegetable transplants grown for sale to consumers. 

pyrethrins
(PyGanic EC 1.4 IIOG, PyGanic EC 5.0 IIOG) (PyGanic SpecialtyOG) REI 12h, Group 3A

Aphids, caterpillars, fungus gnat adults, leafhoppers, thrips,  whiteflies.  Bulb, leafy, Cole, fruiting and cucurbit vegetable transplants.  Contact insecticides. Provides rapid knockdown of pests.
pyrethrins & Beauveria bassiana GHA (BotaniGard Maxx) REI 12h, Group 3A and unknown Aphids, beetles, caterpillars, fungus gnats, leafhoppers, plant bugs, spider mites, thrips, whiteflies.  Bulb, leafy, brassica leafy, fruiting and cucurbit vegetable transplants.  Contact insecticides. Natural pyrethrum combined with insect killing fungus.  Do not apply when beneficial insects are present. 

pyrethrins plus PBO
(Pyrethrum TR) REI 12h, Group 3A

Aphids, beetles, fungus gnat adults, leafhoppers, thrips, whiteflies.  Bulb, leafy, brassica leafy, fruiting and cucurbit vegetable transplants.  Contact insecticide. See label for specific directions for placement and use for successful application.
pyrifluquinazon (Rycar) REI 12h, Group 9B  Aphids and whiteflies. Cucumber, lettuce, pepper and tomato.  Contact insecticide with ingestion and translaminar activity.  Thorough spray coverage is needed. 

pyriproxyfen
(Distance Insect Growth Regulator) REI 12h, Group 7C

Foliar spray for whiteflies, thrips (suppression), aphids (suppression). Apply as a sprench (growing media surface spray) or drench for fungus gnat and shore fly larvae. Indoor-grown fruiting vegetables. Do not apply to tomato varieties less than one-inch in diameter.  Insect growth regulator. See label for plant safety information. 

spirotetramat
(Kontos) REI 24h, Group 23

Aphids (suppression), broad mites, cyclamen mites, leafhoppers, spider mites, thrips immatures (suppression), whiteflies. 

Fruiting and leafy vegetable transplants for resale to consumers. 

Systemic insecticide for foliar and drench application.  See label for plant safety information. 

sulfur

(Microthiol DisperssOG) REI 24 h, Group M02 

Broad mites (pepper), spider mites.  Many vegetables.  Contact miticide/fungicide. 

thiamethoxam
(Flagship 25 WG) REI 12h, Group 4A

Fruiting vegetables: aphids, flea beetles, leafhoppers, whiteflies.

Cucurbit vegetables: aphids, flea beetles, cucumber beetles (suppression), leafminers (suppression), whiteflies. 

Foliar application to vegetable plants grown for resale to consumers. See label for specific types of fruiting and cucurbit vegetables.

Systemic insecticide for foliar or drench application for transplants only for resale to consumers. 

The symbol OG indicates a pesticide is listed by the Organic Materials Review Institute (OMRI) as approved for use in certified organic production.

This information is supplied with the understanding that no discrimination is intended and no endorsement implied. Due to constantly changing regulations, we assume no liability for suggestions. If any information in these tables is inconsistent with the label, follow the label.

 

Transplant Weed Management

In greenhouses, weeds are primary hosts of aphids, whiteflies, thrips, mites, slugs and diseases. Low growing weeds help maintain moist conditions, a favorable environment for fungus gnats and shore flies. Many common greenhouse weeds such as chickweed, oxalis, bittercress, jewelweed, dandelion and ground ivy can become infected with tospoviruses including impatiens necrotic spot virus (INSV) and tomato spotted wilt virus (TSWV), though they show few symptoms. Thrips can then vector the virus to susceptible vegetable crops. Weeds can also carry other plant damaging viruses that are vectored by aphids. Integrated weed management includes sanitation and physical barriers, along with direct controls, such as hand weeding and  selective use of postemergence herbicides.

The use of a physical barrier such as a weed block fabric is an effective method to limit weed establishment on greenhouse floors. The weed fabric should be left bare so it can be easily swept. Covering the weed fabric with gravel makes it difficult to remove any spilled potting media, which provides an ideal environment for weed growth. Regularly pull any escaped weeds before they go to seed. Repair tears in the weed block fabric.

Overall, it is best to avoid herbicide use in a greenhouse when plants are present. If herbicides are used, read and follow all the information below and consult labels.  If the label does not say that it can be used in the greenhouse, then do not use it.  Herbicides that are not considered volatile in field situations can cause significant injury through vapor movement in warm and enclosed structures.

Few herbicides are labeled for use in a greenhouse due to the potential for severe crop injury or death to desirable plants. This injury may occur in a number of ways including: 1) spray drift if fans are operating at the time of application; and 2) volatilization (changing from a liquid to a gas). Herbicide vapors are then easily trapped within an enclosed greenhouse and can injure plant foliage. Always be sure the herbicide selected is labeled for use in the greenhouse. Carefully follow all label instructions and precautions. It is the applicator's responsibility to read and follow all label directions. Use a dedicated sprayer that is clearly labeled for herbicide use only.

Avoid use of preemergence herbicides in the greenhouse! Preemergence herbicides are applied to soil to prevent the emergence of seedlings. They can persist for many months and in some cases over a year. Preemergence herbicides can continue to vaporize in the greenhouse, causing significant damage to young transplants. Only one preemergence herbicide, indaziflam (Marengo) is labeled for greenhouse use on greenhouse floors in an EMPTY greenhouse.

Postemergence herbicides are applied after the weeds have emerged. Several postemergence herbicides can be used under greenhouse benches and on the floors. Contact herbicides are best applied to small seedlings. Large weeds will be burned but not killed.

 

Herbicides for Use in Greenhouses

Ammonium nonanoate (AxxeOG): REI 4h. Non-selective, contact, postemergence herbicide.  Avoid contact with desirable vegetation.

Caprylic acid and capric acid (Fireworxx OG) REI 12h., Non-selective, contact, postemergence herbicide. Herbicidal soap. 

Glyphosate (Roundup Pro, Roundup Pro Concentrate): REI 4h. Non-selective postemergence herbicides. Translocated/systemic. For use in an empty greenhouse between crops and outside greenhouses.

Pelargonic acid & related fatty acids (Scythe): REI 12h. Non-selective, postemergence, contact herbicide. Cool or cloudy weather may slow down activity. Provides no residual weed control but leaves a strong odor. For use when crops are in the greenhouse.

The symbol OG indicates a pesticide is listed by the Organic Materials Review Institute (OMRI) as approved for use in certified organic production.

Weed Control Outside of Greenhouses

In addition to mowing, herbicides may also be used outside of greenhouses. Before spraying weeds around the greenhouse with any herbicide, close vents to prevent spray drift from entering the greenhouse. Avoid using auxin-type herbicides, such as those labeled for broadleaf weed control in turf or brush killers, or herbicides with high volatility near greenhouses. Select herbicides with low volatility. Greenhouse vents and fans can also draw in herbicide vapors from herbicides that are applied outside the greenhouse causing severe damage.