Potato

Introduction

Potato (Solanum tuberosum) is a cool season crop that produces best yields when temperatures average slightly below 70ºF during the growing season. Potatoes will grow well on a wide range of soils and are especially well suited for New England. The best soil for potatoes is well-drained and medium-textured. Potatoes produced on light, sandy, loam soils generally have a more desirable shape and a brighter skin color than those grown on heavier clay-type soils. Poorly-drained soils favor disease development and may result in reduced plant stands, low yields and poor quality.

Types and Varieties

In addition to the varieties listed below, there is a good list of varieties with resistance to particular diseases in the Cornell Organic Potato Production Guide, available at: https://ecommons.cornell.edu/bitstream/handle/1813/42897/2016-org-potatoes-NYSIPM.pdf?sequence=1

Potato Varieties
Early-Maturing
Algonquin - buff skin, white flesh
Caribe - purple skin, white flesh. Resistant to some common scab and PLRV.
Cala Rosa - red skin, yellow flesh. Resistant to hollow heart.
Chieftan - red skin, white flesh. Scab and late blight resistant.
Dark Red Norland - rich dark red skin, white flesh. Tubers round to oblong. Moderately resistant to common scab, stores well.
Natascha - yellow skin, yellow flesh. Reseistant to Rhizoctinia and PVY
Red Gold - pink skin, yellow flesh. Intermediate resistance to scab.
Satina - yellow skin, yellow flesh. Highly resistant to potato late blight and common scab. Stores well.
Superior - buff-colored skin, white flesh. Oval. Moderately resistant to common scab.
Yukon Gem - yellow skin, yellow flesh. Resistant to scab and late blight.
Yukon Gold - yellow/buff-colored skin, medium yellow flesh. Resistant to net necrosis and has high specific gravity. Storability is excellent with long dormancy.
Mid-Season
Adirondack Blue/Red - deeply colored varieties for mid-season.
Caribou Russet - russet skin, white flesh. Moderately resistant to scab and Verticillium.
French Fingerling - pink skin with yellow flesh that is splashed with pink. Longer tubers than most fingerling varieties. Resistant to scab.
Gold Rush - russet type. Resistant to hollow heart, moderately resistant to Verticillium and scab.
Kennebec - smooth buff-colored skin with white flesh. Some resistance to foliar late blight. Susceptible to scab, RhizoctiniaVerticillium, and pinkeye.
Norland - smooth red skin, white flesh. Moderately resistant to common scab, PVY and PLRV. Sensitive to air pollution (ozone).
Red LaSoda - bright, deep red skin, white flesh. Round to oval tubers. Moderately resistant to early blight, tolerant to heat and drought.
Red Pontiac - red-skin, oblong to round tuber. Fairly drought tolerant.
Late-Maturing
Coastal Russet - long, slightly flattened tubers with moderately russeted skin
Katahdin - round white cultivar, high yield potential. Has some resistance to PVY and PLRV and is tolerant of drought conditions. Susceptible to late blight, common scab.
Russet Burbank - russeted long-tuber cultivar with high specific gravity. Resistant to common scab and blackleg. Highly susceptible to PVY.
Russian Banana - light yellow skin, yellow flesh, banana-shaped tubers. Moderately resistant to common scab.
PVY: potato virus Y; PLRV: potato leafroll virus

Soil Fertility

Lime and fertilizer should be applied according to soil test results and potato variety. If the variety is resistant to common scab, soil pH should be maintained at pH 6.0 to allow for rotation crops. If the cultivar to be raised is common scab susceptible, then the soil pH should be maintained at pH 5.0-5.2. Growers should be aware that acid scab, a scab organism that is active at low soil pH, is found in some areas; in these situations, soil pH should be raised to pH 6.0 and a scab-resistant cultivar utilized.

Nitrogen is the most critical element from the standpoint of yield and quality. Excessive nitrogen can delay maturity, decrease quality and adversely affect fry color for processing crops. Too little nitrogen will reduce yields. For most varieties, the amount of nitrogen per acre is usually 140-150 pounds. Higher rates can be used for late-maturing varieties such as Russet Burbank and slightly less for early-maturing varieties such as Kennebec. Apply P and K according to soil test results.

PLANT NUTRIENT RECOMMENDATION ACCORDING TO SOIL TEST RESULTS FOR POTATO
POTATO NITROGEN (N) LBS PER ACRE PHOSPHORUS (P) LBS P2O5 PER ACRE      POTASSIUM (K) LBS K2O PER ACRE
SOIL TEST RESULTS   VERY LOW LOW OPTIMUM ABOVE OPTIMUM VERY LOW LOW OPTIMUM ABOVE OPTIMUM
Where all Fertilizer is Applied at Planting Time                  
Band Placement at Planting

120-180

200

120

30-60

0-30

175

125

100

0-50

TOTAL RECOMMENDED 120-180 200 120 60 0-30 300* 250* 100 0-50
                   
Where Sidedressing is Used                  
Band Placement at Planting
80-120
200
120
30-60
0-30
175
100
50
0-50
Sidedress before plants are 6" high
40-60
0
0
0
0
125
100
50
0
TOTAL RECOMMENDED 120-180 200 120 30-60 0-30 300 200 100 0-50

*APPLY 125 LB K20/A BROADCAST

Planting 

Because potatoes are propagated vegetatively, diseases can be carried over between generations. Therefore it is important to plant only certified or foundation seed which has met specific conditions for production practices and disease tolerances. Planting good seed is an essential step to producing a high-quality crop.

Seed should be stored at 38-40ºF with relative humidity maintained at 95%. Seed taken from cold storage should not be planted or cut immediately. Tubers should be warmed gradually to 50-55ºF, 7-14 days prior to cutting or planting. Good ventilation and 90% relative humidity should be maintained during this process. Cut seed pieces should be blocky, have at least one eye and weigh 1.5-2 oz.

Amount (hundredweight) of Seed Needed to Plant One Acre

Inches between rows 34 inches 36 inches
Weight of Seed piece 1.5 oz  1.75 oz  2 oz 1.5 oz  1.75 oz  2 oz
INches BETWEEN SEED IN ROW CWT needed per acre CWT needed per acre
6 29 34 39 27 32 37
8 22 25 29 20 24 27
10 17 20 23 16 19 22
12 14 17 19 14 16 18
15 11 14 16 11 13 14

The more uniform in size and weight the seed being planted, the more accurate the planter will perform. The ideal soil conditions for planting potatoes are 50-60ºF and half field capacity for moisture content as these encourage wound healing of seed pieces and rapid growth. A well-prepared seedbed is desirable and will facilitate accurate planting. Over-preparation of the seedbed should be avoided because of crusting and compaction problems. Do not plant cut seed in soil below 45ºF to avoid seed piece decay.

Suggested Seed Spacing

CULTIVAR SPACING IN THE ROW
Kennebec 6-8"
Katahdin, Superior, 7-10" Russet Burbank 7-10"
Russet Burbank, GoldRush 12-16"

Close spacing in the row (e.g. 6-8") aids in reducing tuber size and increases the number of tubers set. Using close spacing can reduce the occurrence of hollow heart and growth cracks. Seed pieces should be planted 2-4" below the soil level; this will reduce problems with sunburned tubers. For rapid emergence, no more than 2" of soil should cover the seed piece after planting. Where seed is planted deeper than 2", drag-off (removal of the excess soil from the top of the hill) may be employed to encourage rapid emergence. Rapid emergence should be encouraged to reduce problems with soilborne pathogens such as Rhizoctonia.

Green Sprouting

The practice of pre-sprouting seed potatoes is called green sprouting or chitting. This accelerates plant emergence and speeds the development of marketable tubers, resulting in a gain of 7-10 days to marketable tubers. This practice is often combined with close plant spacing (about 6"). The tubers are harvested when small and often sold in quart baskets as new potatoes. 

About 6 weeks prior to planting, spread whole seed tubers in open-top crates, boxes or flats, 1 layer deep with the eyes up. Egg cartons for small seed lots work great. Keep them in a warm place (approximately 70ºF) in medium light intensity (bright shade). Direct sunlight is not recommended. The warmth stimulates the development of strong sprouts, which in the presence of light, will remain short and stout and will not easily be broken off during the planting process. Cut the seed into pieces when the sprouts are about 1" in length. Cutting seed pieces prior to green sprouting will dry them out and reduce quality.

Cultivation and Hilling

Hilling allows the use of a shallow planting depth to speed plant emergence, while providing the soil depth necessary later in the season for proper tuber development and protection from sunlight, adverse temperatures, and swings in moisture level. Begin hilling and cultivation operations  after the plants begin to emerge and complete prior to the plants filling half of the row to minimize damage to foliage. Discs, rolling cultivators, hillers or implements with winged cultivator teeth may be used. For best results, hills should be flat and broad rather than narrow and peaked. Cultivation during hilling aids in mechanical weed control and soil-applied herbicides can be incorporated at this time.

Sprout Inhibitors

Sprout inhibitors should be used only in conjunction with good storage management. Federal law requires that shipping containers carrying potatoes treated with postharvest sprout inhibitors be labeled with the chemical name of the inhibitor. When small bags are shipped in master containers, only the master container needs to be labeled. Do not treat seed potatoes.

Field Application: Apply 3 lb. a.i. maleic hydrazide/A to healthy, green, non-water-stressed potato vines at least 2 weeks before application of any vine killer. Apply when most of the tubers are 1.5"-2" in diameter. If rain comes within 24 hours of application, effectiveness will be reduced. Do not apply at temperatures above 85ºF. See label for additional information.

Postharvest Custom Applications:  Bulk storage equipped with good ventilation through the pile or pallet box storages can be treated with an aerosolized form of chloropropham (CIPC), sold under a variety of trade names, or Amplify (2,6-diispropylnaphtalene), applied to the storage area by licensed custom applicators. Application should be only after harvest cuts and bruises have healed (two to three weeks after harvest). Low doses can increase internal sprouting. Seed potatoes should not be placed in treated storage at any time. These are also available as emulsifiable concentrates added to wash water for prevention of sprouting in marketing channels. Do not use the herbicide formulation for sprout control. 

Postharvest Application: Sprout Torch (clove oil) can be used as an aerosol or a spray to temporarily eliminate sprouts on potatoes in storage. Do not use on stored seed potatoes.  Do not allow vapors to come in contact with storage areas used for seed potatoes within 60 days of storing seed potatoes.  Do not apply in the field.

Vine Desiccation

Potato vines should be desiccated approximately twenty-one days prior to harvest to ensure good skin set on tubers that are to be stored.  Growers should be aware that rapid vine desiccation, whether from chemical or mechanical methods, could cause stem-end discoloration.

Mechanical desiccation practices, such as mowing or rotobeating, is not recommended for seed production.  Care should also be taken not to rotobeat so vigorously as to promote a Fusarium infection at the stolon attachment on tubers.

Organic methods of vine killing: Potatoes need 2-3 weeks between vine kill and harvest to promote tuber maturity and adequate skin set. Mature skin protects tubers from disease, resists skinning and bruising during harvest and transport, and prolongs tuber storage life. Optimally, vine killing is accomplished mechanically using a flail mower. A flame weeder might be used several days after mowing to assure complete vine kill. Care should be taken to minimize damage to tubers by mowing equipment or by dislodged rocks that can also injure tubers. Vines can also be allowed to senesce naturally by reducing water applications in some cultivars. Another option is to allow frost to kill the vines. However, potatoes left to mature in the ground for 2- 3 weeks after a frost are susceptible to damage by additional frosts and disease.

Defoliants/Dessicants/Harvest Aids for Potato

With chemical desiccation, rates should be reduced if potato plants are stressed.  Please refer to the label of the product being used. Thorough coverage is important for all these products as they are contact herbicides. Field observations suggest the following ranking of desiccants in terms of speed of stem desiccation: paraquat (fastest) > diquat > glufosinate (slowest). This implies that the risk of stem end discoloration is greater with paraquat than with the other vine desiccants.

Please note that potato plants are susceptible to diseases and should be protected from potato late blight as long as green plant material is visible

NOTE: ALWAYS FOLLOW LABEL INSTRUCTIONS. The information provided here is based on product labels at the time of writing. If there is any discrepancy between the label and the information below, follow label instructions. The current label for any given product is "the law" regarding its application.

carfentrazone (Aim EC): PHI 7d, REI 12h, Group 14.  Apply 3.2 to 5.8 fl oz/A to potatoes in the later stages of senescence for desiccation of potato foliage and vines. AIM EC will also desiccate late season susceptible broadleaf weeds to aid in tuber harvest. Adequate desiccation is achieved within 14 days after the initial treatment is applied. If the potato crop is in the active vegetative growth stage when desiccation is initiated, two applications may be required to provide desiccation of leaf and stem tissue (not to exceed 11.6 fl oz/A per season). Dense potato canopy, large plant size and environmental conditions not conducive to product absorption or activity will reduce initial application efficacy and increase the need for a second application. If a second application is necessary, apply at 7 to 14 days after the first application. Thorough coverage of the potato plant to be desiccated is essential. Use a sufficient volume of water to obtain thorough coverage of the potato leaves and vines.

diquat (Reglone): PHI 7d, REI 12h. Suitable for seed and storage. Apply 1 to 2 pt/A. Always use a spray adjuvant (0.1 to 0.5% v/v NIS). Rainfast in 30 minutes. A second application may be made depending on density of vine growth. A 5 day interval is recommended between applications. Not to exceed 4 pt/A per season. Minimum spray volume of 20 gal/A.

glufosinate-ammonium (Rely 280): PHI 9d, REI 12h. NOT for seed. Apply 21 fl oz/A at the beginning of natural senescence of potato vines. Do not split this application or apply more than one application per harvest. Potato varieties with heavy or dense vines may require an application of another desiccation product to complete vine desiccation. Thorough coverage of the potato vines to be desiccated is essential. Use a sufficient volume of water (20 to 100 gpa) to obtain a thorough coverage of the potato vines. Vary the gallons of water per acre and the spray pressure as indicated by the density of the potato vines to assure thorough spray coverage. Increase the spray volume to at least 30 gallons of water per acre when the potato vine canopy is dense or under cool and dry conditions. Apply with the spray boom as low as possible to achieve thorough coverage of the potato vines for best control and to minimize drift potential. Do not make more than one application per year and do not exceed 21 fl oz/A per application. Not for use on potatoes grown for seed.

paraquat (Parazone 3SL): PHI 3d, REI 24h. Maine and Massachusetts only. For Fresh Market potatoes only. Not registered as a vine desiccant for storage or for seed potatoes. Potatoes must be harvested promptly after desiccation and immediately processed or consumed. Storage may result in tuber decomposition. Apply 0.7 to 1.3 pt/A in minimum spray volume 20 gal/A. Split applications may be made with a minimum of 5 days between applications.  Do not apply more than 2.6 pt/A per season.  Always use either NIS at 0.125% v/v (if NIS is less than 75% surface-active agent use 0.25% v/v), or COC at 1.0% v/v.  Rainfast in 30 minutes.  Do not apply to drought-stressed potatoes.  Application to immature potato foliage will not give complete desiccation.

pelargonic acid (Scyth): REI 12 hr. Use 5-10% v/v solution in 75-200 gal/A. Repeat application as required to maintain desirable level of desiccation.

pyraflufen-ethyl (Vida):  PHI 7d, REI 12h.  Apply when the crop is in the early stages of senescence for best results.  Apply up to 5.5 fl oz/A. The product may be tank-mixed or used in sequence with other desiccant products for improved desiccation.  Minimum spray volume is 20 gal/A.  A second application may be made (min 7 day interval). Do not exceed 11 fl oz/A per season. Label suggests that it may not be effective in burning down grassy weeds.

Harvest

Premature harvesting can result in reduced yields and lower specific gravity. On the other hand, if harvesting is delayed too long, frost and diseases can cause serious losses. Proper operation of the harvesting equipment and careful handling can reduce the amount of damage from bruising. Potatoes should not be allowed to fall more than 4-6" and all equipment surfaces should be padded. The ideal temperature during harvest is 60-70ºF. If potatoes are harvested at temperatures below 55ºF, considerable bruising is likely to occur. If tubers are harvested during hot weather (above 80ºF) and they cool off slowly, the likelihood of storage rot is increased. Information on bruise testing is available from the University of Maine Cooperative Extension.

Storage

Healing of cuts and bruises is most rapid at high relative humidity (95%) with a tuber temperature of 50-60ºF and adequate through-the-pile ventilation. This temperature should be provided for 2-3 weeks at the beginning of the storage period. This process is called suberization. Effective suberization will reduce evaporative weight loss and prevent rot organisms from entering damaged tubers. After suberization, the temperature should be lowered gradually to 40ºF for tablestock or seed or maintained at 50ºF for chip stock varieties. When a rot potential such as field frost, late blight or ring rot is present, the curing period should be eliminated, the temperature dropped and the ventilation increased. The crop should be utilized as soon as possible.

An important aspect of potato pest control is to provide a pathogen-free storage environment. All storage and potato handling equipment surfaces should be thoroughly cleaned and disinfected prior to handling and placing the crop into storage. Surfaces should be well moistened by the disinfectant spray. Spray bin walls until there is a slight runoff.  Several disinfectant materials are available: sodium hypochlorite products (Agclor) and peracetic acid products, hydrogen peroxide, and hydrogen dioxide products (GreenClean Liquid 5.0, PeroxySan X15, Sanidate, Storox). Please consult the labels for specific directions.

Temperature control is best achieved with forced air ventilation that is controlled thermostatically by an air proportioning system. Air flows should not exceed 1.0 cu ft/cwt/min. Storage relative humidity should be as high as possible without causing condensation on the storage walls and ceilings. Good insulation properly protected with a vapor barrier reduces danger of condensation.

Pre-storage Fungicide Treatment

Treatment of potatoes (seed and tablestock) with thiabendazole (Mertect 34ºF) as they go into storage has produced excellent control of Fusarium dry rot in storage. However, resistant isolates of Fusarium are now common. Preventing cuts and bruises is the best defense against this disease. Growers may consider, as an alternative, treatment of tubers going into storage with products containing mono-and di-potassium salts of phosphorus acid (Phostrol) to reduce the tuber-to-tuber spread of potato late blight and pink rot as the tubers enter storage. These chemicals should be applied uniformly in a fine mist or fog as tubers pass over a roller table or bin loader. The rolling motion will facilitate even coverage. Do not saturate the tubers.

Disease Control

DISEASE CONTROL NOTE: For the disease control products listed below, a product trade name and formulation are provided for each active ingredient (common name) as an example of rates, preharvest interval (PHI), restricted entry interval (REI), and special instructions. In many cases, there are other products available with the same active ingredient. Please see Table 25 and Fungicides and Bactericides Alphabetical Listing by Trade Name for more information on products with the same active ingredients.

The symbol OG   indicates a product is listed by the Organic Materials Review Institute (OMRI) as approved for use in organic production. See Organic Certification section for more details.

Seed Piece Treatment (Fungi)

Potato seed treatment is one of the more overlooked portions of a whole-season disease control program. Properly suberized and properly treated seed will provide a better, more uniform stand of plants. Proper application of the appropriate material is necessary. Too much chemical may prove phytotoxic. Inadequate coverage may not totally protect the seed-piece. Dust formulations are preferable for cut seed. CAUTION: Dip treatments may spread bacteria to seed pieces which were previously not affected. NOTE: Many of these seed treatments are now formulated with Douglas fir or alder bark as a carrier. Improved healing of the cut surface has been reported with these products. Some seed treatments can be purchased combined with imidacloprid. Do not use treated seed potatoes for feed or food purposes.

azoxystrobin plus mefenoxam (Quadris Ridomil Gold SL): 0.82 fl oz/1000 row feet; PHI 0d, REI 0h, Groups 11 & 4.

Bacillus subtilis strain ENV503 (Companion MaxxOG): 2.0 fl oz/100 lb cut seed pieces; PHI 0d, REI 4h, Group BM02. For seed cuttings dip. See label for additional application methods.

cymoxanil (Curzate 60 DF): 0.25 oz/100 lb cut seed pieces; REI 12h, Group 27. For seedborne late blight. Must be applied in a tank mix with another registered product. Do not use treated seed pieces for food or feed purposes.

fenamidone (Reason 500 SC): 0.15 fl oz/100 lb seed pieces; PHI 14d, REI 12h, Group 11. For seedborne late blight. See label for application restrictions. NOTE: seed pieces may not be used for food, feed or fodder.

fludioxonil (Maxim PSP): 0.5 lb/100 lb seed-pieces; PHI 0d, REI 12h, Group 12. Apply to cover thoroughly. REI may be reduced - see label for details.

fludioxonil plus mancozeb (Maxim MZ): 0.5 lb/100 lb.; PHI 0d, REI 24h, Groups 12 & M03.

fluopyram plus penflufen (Velum Prime): 13.0 fl oz/A; REI 12h, Group 7; Labeled for soil application. Apply only once per year. See label for application methods and restrictions. 

mancozeb (Dithane F45 Rainshield):  1.6 to 2.5 fl oz/100 lb.; REI 24h, Group M03. Do not use treated seed potato for food or seed purposes.

PCNB (Turfcide 4F, aka Blocker 4F or TerraClor 400): 5.2 to 10.4 fl oz/1000 row ft.; PHI 0d, REI 12h, Group 14. For common scab and stem canker/black scurf. See label for other application methods and restrictions.

Trichoderma harzianum Rifai Strain T-22 (RootShield WPOG):  0.02 to 3 oz/100 lb seed; PHI 0d, REI 4h, Group BM02. See label for additional application methods. May be applied with compatible chemical seed dusts - see label.

Trichoderma harzianum Rifai strain T-22 and T. virens Strain G-41 (BW 240 WPOG): 3 lb/100 lb seed; PHI 0d, REI 4h, Group BM02. Labeled for plant root pathogens. Not effective in cool (below 50°F) and wet soils. See label for additional application methods.

Dickeya, Dickeya black leg (Dickeya dianthicola)

Dickeya dianthicola is a bacterial pathogen within the blackleg complex. In general, Dickeya species are transmitted via seed pieces. Infected seed potatoes are usually non-symptomatic or have non-distinctive rot symptoms. Use sound sanitation practices when handling seed pieces to prevent contamination of other potato lots. The first symptom is poor emergence (skips in a production field) due to rotting seed pieces. Plants that emerge from contaminated seed often wilt and usually have blackened stems that extend upwards from the rotting seed piece. Some affected plants may only appear unthrifty. The internal stem tissue may be discolored. Rotations that include corn followed by brassicas should be avoided prior to planting potatoes. Growers should ensure that they purchase certified seed that has been inspected for Dickeya. Fields where Dickeya has been confirmed should be avoided for the following year. No pesticides are effective for managing Dickeya.

Early Blight (Alternaria solani)  

Leafspots are brown with a bulls-eye appearance and crop losses can be heavy if serious defoliation occurs before or soon after flowering. Apply any of the following fungicides when plants are 4" to 6" tall. Begin applications earlier if late blight is found in your area, or if disease forecast systems recommend beginning a protection program. Repeat at 5 to 7 day intervals, depending on amount of moist weather or dew. Use shorter intervals under cool (60º-70ºF) moist conditions. Incorporate diseased vines after harvest and avoid growing pepper, tomato, and potato in a continuous rotation. Allow tubers to mature fully before harvesting, avoid harvesting when the soil is wet, and prevent mechanical injury during harvest and handling. Proper fertilization and mineral balance will reduce susceptibility of plants to early blight. Disease development, based on weather conditions near your farm, can be monitored on-line (www.newa.cornell.edu).

azoxystrobin (Quadris F): 6.0 to 15.5 fl oz/A; PHI 14d, REI 4h, Group 11.  Do not make more than one application of Quadris  before alternating with fungicides with a different mode of action. Labeled for different diseases, including soilborne/seedling diseases. See label for restrictions.

azoxystrobin plus chlorothalonil (Quadris Opti): 1.6 pt/A; PHI 14d, REI 12h, Groups 11 & M05. See label for tank mix precautions. 

azoxystrobin plus difenoconazole (Quadris Top): 8.0 to 14.0 fl oz/A; PHI 14d, REI 12h, Groups 11 & 3.

Bacillus amyloliquefaciens strain D747 (DoubleNickel 55OG): 0.25 to 3.0 lb/A; foliar application; PHI 0d, REI 4h, Group BM02. For disease suppression only. For improved control; mix or rotate with a chemical fungicide. See label for spray volume calculations.

Bacillus mycoides Isolate J (LifeGard WPOG): 4.5 oz/100 gal water; PHI 0d, REI 4h, Group P06. See label for rates required for different spray volumes.

boscalid (Endura): 3.5 to 4.5 oz/A; PHI 10d, REI 12h, Group 7. See label for restrictions.

chlorothalonil (Bravo Weather Stik): 0.75 pt/A before vines close between rows; 1 to 1.5 pt/A after vines close between rows or when disease severity values are reached; PHI 7d, REI 12h, Group M05.

chlorothalonil plus potassium phosphite (Catamaran): 4.0 to 5.5 pt/A; PHI 7d, REI 12h, Groups M05 & P07.

copper hydroxide (Kocide 3000): 0.5 to 1.75 lb/A; PHI 0d, REI 48h, Group M01. Under severe disease, may be tank mixed with other compatible fungicides labeled for potatoes. See label for instructions.

copper oxichloride plus copper hydroxide (Badge X2OG): 1.0 to 4.0 lb/A; PHI 0d, REI 48h, Group M01. Apply higher rate when disease is more severe. Under favorable disease conditions, can tank mix with other compatible fungicide registered for use in potatoes. See label for instructions.

Cymoxanil plus chlorothalonil (ECHO 459/Cymo Zanil, AKA Ariston): 2.0 pt/A; PHI 14d, REI 12h, Group 27 & M05. See label for restrictions. Note longer pre harvest interval.

famoxadone plus cymoxanil (Tanos): 6.0 oz/A; PHI 14d, REI 12h, Groups 11 & 27. Must be tank mixed with an appropriate contact fungicide with a different mode of action. Do not alternate or tank mix with other Group 11 fungicides.

fenamidone (Reason 500 SC): 5.5 to 8.2 fl oz/A; PHI 14d, REI 12h, Group 11. Do not rotate with other Group 11 fungicides.

fluopyram plus penflufen (Velum prime): 13.0 fl oz/A;  REI 12h, Group 7. Labeled for soil tratment. Apply only once per year. See label for application methods and restrictions. 

fluopyram plus prothioconazole (Luna PRO): 10.0 fl oz/A; PHI 14d, REI 12h, Groups 7 & 3. Do not make more than 2 applications per year.

fluopyram plus pyrimethanil (Luna Tranquility): 8.0 to 11.2 fl oz/A; PHI 7d, REI 12h, Group 7 & 9.

fluxapyroxad plus pyraclostrobin (Priaxor Xemium): 4.0 to 8.0 fl oz/A; PHI 7d, REI 12h, Groups 7 & 11. The use of additives or adjuvantes may improve fungicide performance in potatoes. See label for restrictions.

iprodione (Rovral 4F): 1. to 2.0 pt/A; PHI 14d, REI 24h, Group 2. See label for crop rotation restrictions.

mancozeb (Dithane F45 Rainshield): 0.4 to 1.6 qt/A; PHI 3d, REI 24h, Group M03. See label for application instructions and restrictions. Use of Latron surfactant is recommended.

mancozeb plus copper hydroxide (ManKocide): 1.5 to 5.0 lb/A; PHI 3d, REI 48h, Groups M03 & M01.

mancozeb plus zoxamide (Gavel 75DF): 1.5 to 2.0 lb/A; PHI 3d, REI 48h, Groups M03 & 22. Addition of a spreading/penetrating type of adjuvant is recommended. Make no more than 2 consecutive applications before alternating with another fungicide with a different mode of action. 2-3 gallons of spray are generally optimum.

mandipropamid plus difenoconazole (Revus Top): 5.5 to 7 fl oz/A; PHI 14d, REI 12h, Group 40 & 3.

metconazole (Quash SC): 2.5 to 4 fl oz/A; PHI 1d, REI 12h, Group 3.

metiram (Polyram 80 DF): 1.5 to 2.0 lb/A/100 gal water; PHI 3d, REI 24 h, Group M03. See label for application methods, precautions, tank-mixing restrictions.

polyoxin D zinc salt (VeggieTurbo 5S, AKA OSO 5% SC): 6.5 to 13.0 fl oz/A; foliar or chemigation; PHI 0d, REI 4h, Group 19. See label for application instructions.

propamocarb  hydrochloride (Previcur Flex): 0.7 to 1.2 pt/A; PHI 14d, REI 12h, Group 28. Must be tank mixed with a contact fungicide. See label for rates and timing.  

pyraclostrobin (Headline SC): 6.0 to 9.0 fl oz/A; PHI 3d, REI 12h, Group 11. Do not alternate with other Group 11 fungicides.

pyraclostrobin plus metiram (Cabrio Plus): 2.0 to 2.9 lb/A; PHI 3d, REI 24h, Group 11 & M03.

pyraclostrobin plus dimethomorph (Cabrio Team): 26.0 oz/A, PHI4d, REI 12h, Groups 11 & 40.

pyrimethanil (Scala SC): 7.0 fl oz/A; PHI 7d, REI 12h, Group 9.

trifloxystrobin (GEM 500 SC): 3.0 to 3.8 fl oz/A; PHI 7d, REI 12h, Group 11.

trifenyltin hydroxide (Super Tin 80 WP): 2.5 to 3.75 fl oz/A; PHI 7d, REI 48h, Group 30. Restricted use pesticide. Not registered for use in VT, NY, and CT. See label for details.

Late Blight (Phytophthora infestans)

Late blight can occur from infected seed potatoes or infected tubers overwintered in the field. New strains of P. infestans introduced into the region are resistant to metalaxyl. Do not leave cull piles of potatoes in the field. The fungicides used for early blight have some protective ability against Phytophthora but cannot be relied on to provide significant control. If late blight is reported within 0.5 mile, begin applications of an appropriate fungicide. Disease progression throughout the US can also be monitored (www.usablight.org). Plants with significant disease should be plowed under. Check with your local extension specialist for the availability of special exemption fungicides. Disease development, based on weather conditions near your farm, can be monitored on-line (www.newa.cornell.edu).

ametoctradin plus dimethomorph (Zampro): 11 to 14.0 fl oz/A; PHI 4d, REI 12h, Groups 45 & 40. Do not make more than 2 applications before alternating to a labeled fungicide with a different mode of action.

azoxystrobin plus chlorothalonil (Quadris Opti): 1.6 pt/A; PHI 14d, REI  12h, Groups 11 & M05. See label for tank mix precautions. 

Bacillus amyloliquefaciens strain D747 (CX 9030, AKA DoubleNickel 55OG): 0.25 to 3.0 lb/A; above ground application; PHI 0d, REI 4h, Group BM02. Disease suppression only. For improved control, mix or rotate with a chemical fungicide. See label for other application methods and rates.

Bacillus mycoides Isolate J (LifeGard LCOG): 1.0 gal/100.0 gal water; PHI 0d, REI 4h, Group P06. See label to determine concentration for different spray volumes. Apply in an alternating or tank mix program with labeled fungicides. See label for additional information.

chlorothalonil (Bravo Weather Stik): 0.75 pt/A before vines close between rows; 1.0 to 1.5 pt/A after vines close between rows or when disease severity values are reached; PHI 7d, REI 12h, Group M05.

chlorothalonil plus potassium phosphite (Catamaran): 4.0 to 5.5 pt/A; PHI 7d, REI 12h, Groups M05 & P07. Do not apply in a solution having a pH of less than 6.5. See label for tank mix restrictions.

copper hydroxide (Kocide 3000OG): 0.5 to 1.75 lb/A; PHI 0d, REI 48h, Group M01.  Do not apply in a spray solution having a pH less than 6.5 or tank mix with Aliette. See label for tank mix restrictions.

copper oxychloride plus copper hydroxide (Badge SC): 1.0 to 4.0 lb/A; PHI 0d, REI 48h, Group M01. Apply up to 4lb/A when disease is more severe. Under favorable disease conditions, can tank mix with other compatible fungicide registered for use in potatoes.

cyazofamid (Ranman 400SC): 1.4 to 2.75 fl oz/A; PHI 7d, REI 12h, Group 21. Do not make more than 1 application before alternating with a fungicide with a different mode of action. Addition of an organosilicon surfactant may be desirable. See label for restrictions.

cymoxanil (Curzate 60 DF): 3.2 oz/A; PHI 14d, REI 12h, Group 27. Use only in combination with a labeled rate of a protectant such as manzate, chlorothalonil or triphenyltin hydroxide.

cymoxanil plus chlorothalonil (ECHO 459/Cymoxanil 61, AKA Ariston): 2.0 pt/A; PHI 14d, REI 12h, Groups 27 & M05. Must be applied in a tank mix with a fungicide with a different mode of action. Do not make more than 2 sequential applications before alternating to a non-Group M5.

dimethomorph (Forum): 4.0 to 6.0 fl oz/A; PHI 4d, REI 12h, Group 40. Must be applied in a tank mix with a fungicide with a different mode of action. Do not make more than 2 sequential applications before alternating to a different mode of action when using lower labeled rate. See label.

famoxadone plus cymoxanil (Tanos): 6.0 to 8.0 oz/A; PHI 14d, REI 12h, Groups 11 & 27. Must be tank mixed with an appropriate contact fungicide with a different mode of action. Do not alternate or tank mix with other Group 11 fungicides.

fenamidone (Reason 500 SC): 5.5 to 8.2 fl oz/A; PHI 14d, REI 12h, Group 11. Do not make more than one application of Reason before alternating to a fungicide with a different mode of action.

fluazinam (Omega 500F): 5.5 fl oz/A; PHI 14d, REI 12h, Group 29. Must be applied in a tank mix with a fungicide with a different mode of action. Do not make more than 2 sequential applications before alternating to a non-group 40.

mancozeb (Dithane F45 Rainshield): 0.4 to 1.6 qt/A; PHI 3d, REI 24h, Group M03.

mancozeb plus copper hydroxide (ManKocide): 1.5 to 5.0 lb/A; PHI 3d, REI 48h, Groups M03 & M01. 

mancozeb plus zoxamide (Gavel 75DF): 1.5 to 2.0 lb/A; PHI 3d, REI 48h, Group M03 & 22. Increase the use rate according to vine development.

mandipropamid plus difenconazole (Revus Top): 5.5 to 7.0 fl oz/A; PHI 14d, REI 12h, Groups 40 & 3. Addition of a spreading/penetrating type of adjuvant is recommended.  Make no more than 2 consecutive applications before alternating with another fungicide with a different mode of action.

mefenoxam plus chlorothalonil (Ridomil Gold Bravo SC): 2.5 pt/A; PHI 14d, REI 48h, Groups 4 & M05. See labels for details and restrictions.

mefenoxam plus copper hydroxide (Ridomil Gold Copper): 2.0 lb/A; PHI 14d, REI 48h, Groups 4 & M01. Do not plant any crop which is not registered for use with Ridomil Gold active ingredient in treated soil for a period of 12 months.

mefenoxam plus manzate (Ridomil Gold MZ): 2.5 lb/A; PHI 3d, REI 48h, Groups 4 & M03. Do not plant any crop which is not registered for use with Ridomil Gold active ingredient in treated soil for a period of 12 months.

oxathiapiprolin plus chlorothalonil (Orondis Opti): 1.75 to 2.5 pt/A; PHI 7d, REI 12h, Groups 49 & M05. See label for product use restrictions.

oxathiapiprolin plus mandipropamid (Orondis Ultra): 5.5 to 8.0 fl oz/A; PHI 14d, REI 4h, Groups 49 & 40. See label for product use restrictions.

phosphorus acid (Fosphite): 1.0 to 5.0 qt/10 to 20 gal water; PHI 0d, REI 4h, Group P07. Do not apply to heat or moisture stressed plants. See label for application rate details and additional precautions.               

propamocarb hydrochloride (Previcur Flex): 0.7 to 1.2 pt/A; PHI 14d, REI 12h, Group 28. Must be tank mixed with a contact fungicide. See label for rates and timing.

pyraclostrobin (Headline SC): 6.0 to 12.0 fl oz/A; PHI 3d, REI 12h, Group 11.  Do not rotate with other Group 11 fungicides.

pyraclostrobin plus metiram (Cabrio Plus): 2.9 lb/A; PHI 3d, REI 24h, Groups 11 & M03.

pyraclostrobin plus dimethomorph (Cabrio Team): 26.0 oz/A; PHI 4d, REI 12h, Groups 11 & 40. DO NOT make moe than one application of Cabrio Team before alternating to a labeled fungicide with a nonQol (Group 11) mode of action for at least one application.

trifloxystrobin (GEM 500 SC): 3.8 fl oz/A; PHI 7d, REI 12 h, Group 11. Must be tank mixed with a protectant.

triphenyltin hydroxide (Super Tin 80 WP): 2.5 to 3.75 oz/A; PHI 7d, REI 48h, Group 30. Restricted use pesticide. Not registered for use in VT, NY, and CT. See label for details. Lower rate may be used in combination with another registered fungicide.

zoxamide plus chlorothalonil (Zing!): 30.0 to 34.0 fl oz/A; PHI 7d, REI 12h, Groups 22 & M05.

Common Scab (Streptomyces spp.)

Scab is caused by the soilborne bacterium Streptomyces scabies. The disease tends to be prevalent when soil is dry during tuber initiation, soil pH is above 5.2, and non-decomposed manure is used as fertilizer. Continuous cropping of potato will also increase the disease. When planting susceptible varieties, avoid fields with a history of scab. When scab is present, rotate out of potatoes for at least 2 years. Beets, carrots, radish and some weeds can also be hosts. Maintain soil pH at 5 to 5.2. Irrigation scheduling may have a direct affect on the incidence of common scab during tuberization. Maintaining soil at moisture levels near field capacity during the 2 to 6 weeks following tuber initiation will inhibit infection. However maintaining high soil moisture may be difficult in some soils, and it is possible that other disease problems may be aggravated by excessive irrigation.

Varieties with some resistance to scab include Nooksack, Russet Burbank, Dark Red, Norchip, Norland, Pike, Salem, and Superior. Allegany, Andover, Atlantic, Chieftain, Elba, Genesee, Monoma, Reba, and Redsen are moderately resistant. Several of the fingerling types also have some resistance. Katahdin, Kennebec, and Snowden are moderately susceptible. Chippewa, Kanona, Norwis, Shepody, Russet Norkotah, Defender, and Yukon Gold are some of the more susceptible lines.

Pythium Leak or shell rot (Pythium spp.)

Leak can be a problem in stored potatoes, especially bruised, immature potatoes harvested in hot weather. Symptoms include spongy, wet internal rot of tubers with diseased flesh separated from healthy tissue by a dark boundary line. In advanced infections, hollow cavities form and all that remains of some infected tubers are tuber shells with thin papery skins.

mefenoxam (Ridomil Gold SL): 0.42 oz/1,000 linear ft (in furrow); PHI 0d, REI 48h, Group 4. Apply as a 6-8 inch band at planting in a minimum of 3 gal of water. See label for pre-plant incorporated application rates and restrictions. Can be supplemented with a phosphorous acid product. See label for details. Do not plant any crop which is not registered for use with Ridomil Gold active ingredient in treated soil for a period of 12 months. 

mefenoxam plus chlorothalonil (Ridomil Gold Bravo SC): 2.5 pt/A; PHI 14d, REI 48h, Groups 4 & M05. See label for application methods and restrictions.

mefenoxam plus copper hydroxide (Ridomil Gold Copper): 2.0 lb/A; foliar applied. PHI 14d, REI 48h, Groups 4 & M01. See label for application methods and restrictions.

mefenoxam plus manzate (Ridomil Gold MZ WG): 2.5 lb/A; PHI 3d, REI 48h, Groups 4 & M03. See label for application methods and restrictions.

phosphorus acid (Phostrol): 3.75 to 10.0 pt/A (in furrow) or 2.5 to 10.0 pt/A foliar applied; PHI 0d, REI 4h, Group P07. For suppression of leak, combine the in-furrow treatment of phosphorous acid with a mefenoxam fungicide (Group 4). Additional in-season foliar applications of a phosphorous acid containing fungicide tank mixed with a mefenoxam containing fungicide may be necessary to achieve adequate control. See labels for specific rates.

Verticillium and Fusarium Wilt

Verticillium and Fusarium are soil-borne fungi that cause vascular wilts of potato. They can be introduced into fields by contaminated seed or soil. Continual potato production tends to result in an increase in wilt disease. A combination of lesion nematodes and Verticillium results in early death. Rotation with non-susceptible crops such as grasses will reduce disease. Destruction of infected potato vines by tillage encourages rapid decomposition and lessens the build-up of soil inoculum. At this time, there are no varieties resistant to Fusarium wilt. Avoid highly susceptible cultivars and start with certified, disease-free seed pieces.

azoxystrobin plus benzovindiflupyr (Elatus): 0.5 fl oz/1000 linear row ft; REI 12h, Groups 11 &7. For suppression only; in furrow use only. Do not make foliar applications. See label for restrictions.

Bacillus subtilis strain QST 713 (MinuetOG): 12.0 to 24.0 oz/A (soil); PHI 0d, REI 4h, Group BM02.

ethaboxam (Elumin): 8 fl oz/A; REI 12h. Group 22. Make in-furrow or sidedress applications. Do not make more than 2 applications per year. See label for restrictions. 

Trichoderma asperellum, T. gamsii (Bio-tam 2.0OG): See label for rates; REI 4h, Group NC.

Potato Leaf Roll Virus (PLRV)

Purchase certified seed to limit viruses. Consult seed producers to determine what the certification covers. Destroy cull piles and volunteer plants. Potato leafroll virus is the most serious virus disease of potatoes in New England and can result in significant yield reductions. The virus is transmitted by aphids in a persistent manner (aphids remain viruliferous for exteded periods). The virus can overwinter in unharvested tubers which may develop into virus-infected volunteer plants. Plant virus-free, certified seed. Remove volunteer plants. Rogue plants with virus symptoms. When populations of aphids reach economic thresholds, treatment is warranted. Do not use any of last year's potato harvest for seed.

Potato Virus S (PVS), Potato Virus A (PVA), Potato Virus X (PVX)

Purchase certified seed to limit viruses. Consult seed producers to determine what the certification covers. Destroy cull piles and volunteer plants. Do not keep potatoes for seed. These viruses may occur singly or in combination. PVY, PVS and PVA are spread by aphids in a nonpersistent manner. PVX is not known to be spread by aphids but is easily spread by plant-to-plant contact, farm machinery or cultural practices. Plant certified virus-free seed. Plant early, use resistant varieties, and control aphid populations.

Potato Virus Y

Potato Virus Y (PVY) has a worldwide distribution and is one of the most important viruses affecting potato. Three main strains have been described that differ in distribution and symptomatology. Symptoms vary widely with cultivars and virus strain combinations, ranging from mild mosaic to severe foliar necrosis. One strain can cause a symptomless current season infection that leads to next-generation infection. Primary symptoms of PVY include mottling, yellowing, leaf drop, and premature plant death. Potato with secondary infection exhibit stunting, mottling, stem necrosis, and crinkled leaves. Symptoms may be suppressed by low or high temperatures. Tuber symptoms generally correspond to leaf effects. PVY is the type member of the plant virus family Potyviridae, the largest and most significant virus group, and has caused significant losses in agricultural, forage, and horticultural crops. Hosts include Solanaceous, Leguminous, and Chenopodiaceae (i.e. spinach, chard, beets) families.

Infection is transmitted in a non-persistent manner (characterized by very short acquisition and inoculation times of seconds to minutes) by more than 25 species of aphids and may also occur mechanically by foliar or tuber contact. Long distance transport is by winged aphids Use certified, disease-free seed tubers to reduce primary inoculum. Insecticides may slow the spread of disease within a crop, but may actually increase insect probing and be counterproductive because only a few seconds of insect feeding is sufficient for virus transmission. Minimize contact disease spread by minimizing mechanical damage during cultivation, spraying, and harvest. Sanitize seed cutting equipment between seed lots. Remove virus-infected plants. 

Plant resistant varieties: Villeta Rose, Eva, Rio, Grande Russet, and Premier Russet.

Insect Control

NOTES:  For the insecticides listed below, one product trade name and formulation is provided for each active ingredient (AI) as an example of rates, preharvest interval (PHI), restricted entry interval (REI), and special instructions. In many cases, there are other products available with the same AI. Please see Table 26 and Insecticides Alphabetical Listing by Trade Name for more information on these insecticides.

The designation (Bee: L, M, or H) indicates a bee toxicity rating of low, moderate, or high. See the Protecting Honeybees and Native Pollinators section for more details.

The symbol * indicates a product is a restricted use pesticide. See Pesticide Safety and Use for more details.

The symbol OG   indicates a product is listed by the Organic Materials Review Institute (OMRI) as approved for use in organic production. See Organic Certification section for more details.

Aphids, Potato (Macrosiphum euphorbiae), Green Peach (Myzus persicae) and others 

Green peach aphids (GPA) and potato aphids (PA) are the most common colonizing aphids in potato, while buckthorn (Aphis nasturtii) and melon aphid (Aphis gossypii) and foxglove aphid (Aulacorthum solani) are occasional or localized pests. There are other species of aphids that do not colonize potatoes but may transmit virus as they probe potatoes in search of a host plant. 

Aphids vector Potato leafroll virus (PLRV) in a persistent manner and Potato Virus Y (PVY) in a non-persistent manner. PLRV and some strains of PVY are capable of causing internal discoloration of tubers, and some strains of PVY can cause both internal and external defects on tubers of some varieties.  Viruses reduce yield and quality in both seed and tablestock potatoes, and tolerance for virus is especially low in seed potato.  GPA is the primary vector of PLRV and an efficient vector of PVY.  Potato, buckthorn and many non-colonizing aphids are also vectors of PVY.  Buckthorn aphids are the smallest of potato-infesting aphids and are more common in northern Maine, where high populations can occur quite early in the season. See green peach aphid in the insect control section of Pepper and melon aphid in the insect control section of Cucumber for more information on these pests.

Potato aphid (PA) is the largest of the colonizing aphids, 3 to 4 mm long, elongated in shape, and may be pink or green. Its antennae are as long as the body, its cornicles are long with dark tips, and on the head between the antennae the tubercles turn outward.  When disturbed, PA may drop off the plant.  There are both winged and wingless forms of adult females who produce live nymphs without mating, about 50 nymphs per 2 weeks. Nymphs are yellowish green or yellowish pink and become reproductive in 2 weeks.  PA overwinters as eggs on plants in the rose family, feeds for several generations after hatching in spring, and colonizes a wide range of weeds, field crops, flowers, and vegetables from June through September. Vegetable crops most affected are potato, field and greenhouse tomato, lettuce, and spinach. PA feeds and builds up on young and growing plants, moving to new hosts as food quality declines. In fall they return to rose, male and female forms mate and eggs are laid. As far north as Virginia, overwintering occurs on crops such as kale and spinach, without an egg stage; in New England, winter greens in tunnels may provide a suitable habitat bridge for PA from one season to the next.

Potato aphids feed first in young growing tips, spreading downward as they multiply.  (By contrast, GPA feeds in lower leaves). Leaves become distorted, with the leaf edges curling downward, and dieback occurs from the tip downward.  Potato plants may be killed at high numbers. Tomatoes show similar leaf symptoms, but blossoms are preferred, and PA colonies cause blossom drop and fruit deformities. See aphids in the insect control section of Greenhouse Tomato for more on biocontrol of PA.

Use disease-free certified seed to reduce the incidence of virus. Plant varieties that are less susceptible to viruses (See Varieties). As with other aphids, naturally occurring predators and parasitoids suppress aphid populations in the field. Use selective or systemic insecticides for Colorado potato beetle to conserve natural enemies of aphids. Spread of PLRV can be prevented when effective foliar sprays are used at threshold. However, insecticides (both systemic and foliar) offer little or no protection against PVY.  Oil sprays have been shown to provide some protection from the virus transmission of non-persistent viruses, but must be reapplied regularly.

Fields should be scouted for aphids starting at 50% plant emergence in seed-producing areas, and starting in June where only fresh market or processing crops are grown. To scout, count all aphids on 25 to 50 fully expanded compound leaves (e.g., 5 per site, 10 sites across the field).  The threshold for insecticide application depends on growth stage and the target market. Thresholds in fresh market and processing potato: before tuber initiation, average 2 aphids/leaf; tuber initiation to 2 weeks before vine kill, average 4 aphids per leaf; and within two weeks of vine kill, average 10 aphids per leaf. Because of the importance of seed production in Maine, the economic threshold for all types of potatoes is lower: when aphids are found on 50% of the plants or 1 winged green peach aphid is found within the field. Because aphids tend to infest the underside of leaves, good spray coverage is needed for foliar sprays.

acetamiprid (Assail 30SG): 2.5 to 4 oz/A; PHI 7d, REI 12h, Bee: M, Group 4A.

alpha-cypermethrin (Fastac* EC): 3.2 to 3.8 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

azadirachtin (Azatin OOG): 4 to 16 oz/A foliar or drench, 4 to 16 oz/100 gal in greenhouses; PHI 0d, REI 4h, Bee: L, Group UN. When using lower rates, combine with adjuvant for improved spray coverage and translaminar uptake.

chlorantraniliprole & lambda-cyhalothrin (Besiege*): 6 to 9 oz/A; PHI 14d, REI 24h, Bee: H, Groups 28 & 3A.

Chromobacterium subtsugae strain PRAA4-1 (GrandevoOG): 2 to 3 lb/A; PHI 0d, REI 4h, Bee: M, Group UN.

clothianidin (Belay): 2 to 3 oz/A for foliar application, 9 to 12 oz/A for soil application, 0.4 to 0.6 oz/100 lbs seed for seed-piece application; PHI 14d, REI 12h, Bee: H, Group 4A. Do not apply treatment between 50% row closure and petal fall. Soil application may be at planting or as a sidedress at ground-crack during hilling (cover with at least 3" of soil).

cyantraniliprole (Verimark): 13.5 oz/A; PHI 0d, REI 4h, Bee: H, Group 28. For soil applications at planting. For suppression of green peach aphid only.

dimethoate (Dimethoate 4EC): 0.5 to 1 pt/A; PHI 0d, REI 48h, Bee: H, Group 1B.

dinotefuran (Venom): 0.3 lb/A foliar or 1.4 to 1.65 lbs/A soil; PHI 7d foliar, REI 12h, Bee: H, Group 4A. Soil application may be applied as a narrow band before planting, in-furrow at planting, or as a sidedress at ground-crack during hilling and immediately covered with soil. For green peach and potato aphid suppression only.

esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A; PHI 7d, REI 12h, Bee: H, Group 3A. For buckthorn and potato aphids.

flonicamid (Beleaf 50SG): 2 to 2.8 oz/A; PHI 7d, REI 12h, Bee: L, Group 9C.

flupyradifurone (Sivanto): 10.5 to 14 oz/A for green peach aphid, 7 to 14 oz/A for other aphids; PHI 7d, REI 4h, Bee:L, Group 4D.

gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 7d, REI 24h, Bee: H, Group 3A.

imidacloprid (Admire Pro): 1.3 oz/A for foliar application, 5.7 to 8.7 oz/A for soil application; PHI 7d foliar, 125d soil, REI 12h, Bee: H, Group 4A.

imidacloprid + mancozeb (TOPS-MZ-Gaucho): 0.75 lb/100 lb seed-pieces; REI 48h, Bee: H, Group 4A. Seed-piece treatment only. Do not make subsequent application of another neonicotinoid (Group 4A) insecticide following a seed-piece treatment. Aids in control of aphids. Not registered in CT or VT.

insecticidal soap (M-PedeOG): 1.25 to 2.5 oz/gal water; PHI 0d, REI 12h, Bee: L. Spray to wet all infested plant surfaces. May need to make repeated applications. For enhanced and residual control, apply with companion labeled aphicide.

lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 7d, REI 24h, Bee: H, Group 3A.

malathion (Malathion 57EC): 1 to 1.5 pt/A; PHI 0d, REI 12h, Bee: H, Group 1B.

methomyl (Lannate* LV): 1.5 to 3 pt/A; PHI 6d, REI 48h, Bee: H, Group 1A.

oxamyl (Vydate* C-LV): 17 to 34 oz/A; PHI 7d, REI 48h, Bee: H, Group 1A. At-planting treatments of systemic aphicides followed by mid-season Vydate application, before previous treatment starts to break down, has provided best season-long control. Note: Vydate L is NOT labeled for potatoes.

petroleum oil (Suffoil XOG): 1 to 2 gal/100 gal water; PHI 0d, REI 4h, Bee: L. Apply as needed.

phorate (Thimet* 20G): 8.5 to 11.3 oz/1000 row ft for light or sandy soils at planting or post-emergence, 13 to 17.3 oz/1000 row ft in heavy or clay soils at planting; PHI 90d, REI 48h, Bee: H, Group 1B. May be applied at planting in sandy or clay soils. Distribute granules evenly in-furrow or band on each side of the row and incorporate. Granules must be incorporated into the soil. May be applied post-emergence on sandy soils only. Place granules on each side of hill at seed-piece level before hilling, 4 to 6 weeks after planting.

pymetrozine (Fulfill): 2.75 to 5.5 oz/A; PHI 14d, REI 12h, Bee: L, Group 9A. Selective control of aphids including potato, melon and green peach. Translaminar. Apply at threshold, before populations build up. The "sticker" in some fungicides may inhibit leaf uptake. Consult label for mixing partners.

pyrethrin (PyGanic EC5.0OG): 4.5 to 17 oz/A; 0.25 to 0.50 oz/gal, 3 gal/1000 sq ft in greenhouse for backpack sprayers; PHI 0d, REI 12h, Bee: M, Group 3A.

sodium tetraborohydrate decahydrate (Prev-AM): 100 oz/100 gal; REI 12h, Bee: L, Group 25. Do not apply in midday sun or mix with copper, sulfur or oils.

spirotetramat (Movento): 4 to 5 oz/A; PHI 7d, REI 24h, Bee: M, Group 23. Must be tank-mixed with a spray adjuvant with spreading and penetrating properties to maximize leaf uptake and sytemicity. Don't use sticker adjuvants. Controls immature stages, may also reduce adult fertility.

sulfoxaflor (Transform WG): 0.75 to 1.5 oz/A; PHI 7d, REI 24h, Bees: H, Group 4C. Do not apply between 3 days prior to bloom and until after petal fall. 

thiamethoxam (Actara): 3 oz/A; PHI 14d, REI 12h, Bee: H, Group 4A.

thiamethoxam (Cruiser 5FS): 0.11 to 0.16 oz/100 lb of seed; REI 12h, Bee: H, Group 4A. Systemic seed treatment. Use only approved equipment for applying liquid seed treatment products to potatoes. See rates based on row spacing on label. For early-season protection.

thiamethoxam (Platinum): 5 to 8 oz/A; REI 12h, Bee: H, Group 4A. Systemic insecticide applied to seed pieces in-furrow during planting, impregnated on dry granular fertilizer before or during planting, or as directed spray at plant emergence or during last hilling operation. Must incorporate into root zone with sufficient irrigation within 24 hours. DO NOT apply as a foliar spray.

Colorado Potato Beetle (Leptinotarsa decemlineata)

Colorado potato beetles (CPB) are 1/2" long by 3/8" wide, oval with a rounded back, and each forewing is yellow with five black stripes. CPB overwinters in the adult stage, primarily in soil (up to 12" deep) in the woods and brushy borders next to host crops, though some burrow into soil in the field. In spring, the beetles search for food plants by walking from the field edges. Heavy feeding may occur on edges on non-rotated fields. If beetles do not find host plants via walking they will fly in search of food.

In the Northeast, CPB survives on solanaceous crops and weeds, including horsenettle, nightshade, eggplant, potato and tomato (primarily seedlings). Once host plants are found adults feed, mate and lay clumps of 30 to 35 bright yellow eggs on the undersides of leaves. Eggs hatch in 7 to 10 days, depending on temperature. The larva is hump-backed, rusty-red with 2 rows of black dots along each side of its body. Feeding damage and larvae are easily seen on leaves. Larvae grow through 4 stages and reach 5/8" long before they drop to the soil and pupate. Because the last stage does 85% of the feeding damage it is critical to control larvae while they are small. Adults emerge from pupae after 10 to 14 days. In southern New England, there is a second generation of eggs, larvae and adults, while in northern New England there is one generation.

Cultural controls. The single most important tactic for CPB management is to rotate potatoes, eggplant and tomato to a field that is at least 200 yards from the previous year's fields. Barriers such as roads, rivers, woodlands, and fields with other crops are helpful. This single practice delays colonization and reduces population densities.

Mechanical barriers such as trench traps, trap crops and straw mulch also delay and reduce infestation. Install plastic-lined trench traps next to overwintering sites at least 1 week before adults emerge. Trenches should be 1' to 2' deep and 6" to 24" wide at the top. They can be U- or V-shaped with side walls sloping at angles between 65° and 90°. Beetles walking from field borders fall into the trench and cannot fly out. Perimeter trap crops may be potatoes planted earlier than the main crop to attract beetles before the main crop emerges, or planted between overwintering sites and this season's crop. Flame, vacuum or spray border crop before beetles move into the main crop. Another approach is to plant 3 to 5 rows of potatoes treated with a systemic insecticide in a perimeter around the field; this treated border will kill up to 80% of the colonizing beetles. Straw mulch around the host crop has been shown to reduce beetle numbers. Late planting may cause beetles to leave the field before potatoes emerge, resulting in lower beetle numbers.

Natural enemies that attack CPB eggs or larvae include twelve-spotted ladybeetle, spined soldier bug, a carabid beetle, Lebia grandis and a parasitic tachinid fly. Beauvaria bassiana has been shown to suppress beetle populations though it does not provide immediate control.

Colorado potato beetles rapidly develop resistance to insecticides. This can happen in as short a time as 1 year and is likely whenever a single class of insecticide is used multiple times against the same population in the same and succeeding years. The population on a single farm may develop resistance in response to management practices on that farm. Resistance to pyrethroids and neonicotinoids exists in parts of New England.

Wherever possible, growers should rotate classes of insecticides and avoid using the same chemistry more than once per year, or better, once every other year. Do not use the same chemical class on successive generations in the same year. There are enough different classes to allow this, if you plan carefully. Note the resistance group number of each insecticide and avoid using chemistries from the same group. Use newer chemistries first.

Do not try to kill every beetle in the field. Potato crops can withstand 15% defoliation without affecting yields. Avoid spraying the beetle in late season, as food reserves in the foliage 2 weeks prior to senescence add little to final tuber bulking.

Scout to determine whether or not a damaging population is present. When using products that control only larvae, scout for eggs, note egg hatch and apply controls before larvae reach third instar. For materials that control all stages, you may wait and scout for adults and larvae to determine the need to apply insecticides.

To use the threshold table below, walk the field in a V-shaped pattern and select 50 potato stalks at intervals, e.g., every 10 to 20 paces, depending on field size. Count adults, large larvae (greater than half-grown) and small larvae (less than half-grown) separately. If the number of CPB is high, an insecticide should be applied; if the number is low, no insecticide is required for that week. If the number of CPB is between high and low, no insecticide should be applied, but the field should be checked in 3 to 5 days. Otherwise, the field should be checked weekly. These thresholds are for mid-season. Late in the season, potato plants can tolerate more defoliation without affecting yields.

Action Thresholds

Life Stage No. of CPB per 50 stalks
  Low High
Adults 15 or fewer 25 or more
Small Larvae 75 or fewer 200 or more
Large larvae 30 or fewer 75 or more

abamectin (Agri-Mek* SC): 1.75 to 3.5 oz/A; PHI 14d, REI 12h, Bee: H, Group 6. Must be mixed with a non-ionic wetting, spreading and/or penetrating spray adjuvant. Do not use binder or sticker type adjuvant. Make first application at 50% egg hatch. If two applications are needed, limit to single application per CPB generation.

acetamiprid (Assail 30SG): 1.5 to 4 oz/A; PHI 7d, REI 12h, Bee: M, Group 4A.

alpha-cypermethrin (Fastac* EC): 3.2 to 3.8 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

azadirachtin (Azatin OOG): 4 to 16 oz/A foliar or drench, 4 to 16 oz/100 gal in greenhouses; PHI 0d, REI 4h, Bee: L, Group UN. For use on young larvae. When using lower rates, combine with adjuvant for improved spray coverage and translaminar uptake.

Beauveria bassiana (Mycotrol ESOOG): 0.5 to 1 qt/A; PHI 0d, REI 4h, Bee: L, Group UN. Treat when populations are low and thoroughly cover foliage. Takes 7 to 10 days after the first spray to see control. Repeat applications may be needed.

beta-cyfluthrin (Baythroid* XL): 1.6 to 2.8 oz/A; PHI 0d, REI 12h, Bee: H, Group 3A.

chlorantraniliprole (Coragen): 3.5 to 7.5 oz/A; PHI 14d, REI 4h, Bee: L, Group 28. Apply as a foliar spray. Do not apply more than twice to one generation or within a 30 day period. 

chlorantraniliprole & lambda-cyhalothrin (Besiege*): 6 to 9 oz/A; PHI 14d, REI 24h, Bee: H, Groups 28 & 3A.

clothianidin (Belay): 2 to 3 oz/A for foliar application, 9 to 12 oz/A for soil application, 0.4 to 0.6 oz/100 lbs seed for seed-piece application; PHI 14d, REI 12h, Bee: H, Group 4A. Do not apply treatment between 50% row closure and petal fall. Soil application may be at planting or as a sidedress at ground-crack during hilling (cover with at least 3" of soil). Will not control CPB in regions where insensitivity to neonicotinoid insecticides has been reported. 

cyantraniliprole (Verimark): 6.75 to 13.5 oz/A for soil applications, 0.46 to 0.75 oz/100lb of seed-pieces; PHI 0d, REI 4h, Bee: H, Group 28. For soil applications at planting and potato seed-piece treatment.

cyromazine (Trigard): 2.66 to 5.32 oz/A; PHI 17d, REI 12h, Bee: M, Group, 17. Insect growth regulator most effective on 1stor 2nd instar larvae. Does not control adult beetles.

deltamethrin (Delta Gold*): 1.5 to 2.4 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.

dinotefuran (Venom): 0.3 lb/A foliar or 1.4 to 1.65 lbs/A soil; PHI 7d foliar, REI 12h, Bee: H, Group 4A. Soil application may be applied as a narrow band before planting, in-furrow at planting, or as a sidedress at ground-crack during hilling and immediately covered with soil.

esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A; PHI 7d, REI 12h, Bee: H, Group 3A.

flupyradifurone (Sivanto): 10.5 to 14 oz/A; PHI 7d, REI 4h, Bee: L, Group 4D.

gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 7d, REI 24h, Bee: H, Group 3A.

imidacloprid + mancozeb (TOPS-MZ-Gaucho): 0.75 lb/100 lb seed-pieces; REI 24h, Bee: H, Group 4A. Seed-piece treatment only. Do not make subsequent application of another neonicotinoid (Group 4A) insecticide following a seed-piece treatment. Aids in control of aphids. Not registered in CT or VT.

indoxacarb (Avaunt): 3.5 to 6 oz/A; PHI 7d, REI 12h, Bee: H, Group 22. Efficacy may be improved by the addition of piperonyl butoxide (PBO).

lambda-cyhalothrin (Warrior* II): 1.28 to 1.92 oz/A; PHI 7d, REI 24h, Bee: H, Group 3A.

ledprona (Calantha*): 12 to 16 oz/A; PHI 0d, REI 4h, Bee: L, Group 35. Most effective on young larvae. 

novaluron (Rimon 0.83EC): 6 to 12 oz/A; PHI 14d, REI 12h, Bee: L, Group 16B. Do not apply to successive generations. Most effective on 1st and 2nd instars. No activity against adult CPB or beneficials.

oxamyl (Vydate* C-LV): 8.5 to 34 oz/A; PHI 7d, REI 48h, Bee: H, Group 1A. NOTE: Vydate L is NOT labeled for potatoes.

permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A; PHI 14d, REI 12h, Bee: H, Group 3A.

phorate (Thimet* 20G): 13 to 17.3 oz/1000 row ft for heavy or clay soils in early season at-planting applications; 8.5 to 11.3 oz/1000 row ft for light or sandy soils in early season post-emergence applications; PHI 90d, REI 48h, Bee: H, Group 1B. Apply at planting in heavy soil. Distribute granules in-furrow or band on each side of the row and incorporate. Granules must be incorporated into the soil. Apply post-emergence on sandy soil. Place granules on each side of hill at seed-piece level before hilling, 4 to 6 weeks after planting.

pyrethrin (PyGanic EC5.0OG): 4.5 to 17 oz/A; 0.25 to 0.50 oz/gal, 3 gal/1000 sq ft in greenhouse for backpack sprayers; PHI 0d, REI 12h, Bee: M, Group 3A.

spinetoram (Radiant SC): 4.5 to 8 oz/A; PHI 7d, REI 4h, Bee: M, Group 5.

spinosad (Entrust SCOG): 3 to 10 oz/A; PHI 7d, REI 4h, Bee: M, Group 5. Controls adults and larvae.

thiamethoxam (Actara): 1.5 to 3 oz/A; PHI 14d, REI 12h, Bee: H, Group 4A.

thiamethoxam (Cruiser 5FS): 0.11 to 0.16 fl. oz/100 lb of seed; REI 12h, Bee: H, Group 4A. See label for rates based on row spacing. Systemic seed treatment. Use only approved equipment for applying liquid seed treatment products to potatoes. For early-season protection.

thiamethoxam (Platinum): 5 to 8 oz/A; REI 12h, Bee: H, Group 4A. Systemic insecticide applied to seed pieces in-furrow during planting, impregnated on dry granular fertilizer before or during planting, or as directed spray at plant emergence or during last hilling operation. Must incorporate into root zone with sufficient irrigation within 24 hours. DO NOT apply as a foliar spray.

zeta-cypermethrin (Mustang*): 3.2 to 4 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.  

Cutworms

Caterpillars hide under the soil surface adjacent to the plant stem during the day and feed after dark. Larvae may feed on leaves, cut stems or even occasionally feed on tubers. For best results, make application between midnight and dawn while cutworms are feeding aboveground. Synthetic pyrethroids (Group 3A) may work best during cool spring weather. See cutworms in the Pepper and Tomato (Outdoor) sections for more information on the black and variegated cutworms.

alpha-cypermethrin (Fastac* EC): 1.3 to 3.8 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

Bacillus thuringiensis aizawai (XenTariOG): 0.5 to 1.5 lb/A; PHI 0d, REI 4h, Bee: L, Group 11. Must be ingested. Apply in evening before larvae are actively feeding. Adherence and weather-fastness will improve with use of an approved spreader-sticker. Use high rate at cool temperatures.

Bacillus thuringiensis kurstaki (Dipel DFOG): 0.5 to 2 lb/A; PHI 0d, REI 4h, Bee: L, Group 11. Must be ingested. Apply in evening before larvae are actively feeding. Adherence and weather-fastness will improve with use of an approved spreader-sticker. Use high rate at cool temperatures.

beta-cyfluthrin (Baythroid* XL): 0.8 to 1.6 oz/A; PHI 0d, REI 12h, Bee: H, Group 3A.

carbaryl (10% Sevin Granules): 20 lb/A; PHI 7d, REI 12h, Bee: H, Group 1A. Apply evenly over soil surface.

chlorantraniliprole & lambda-cyhalothrin (Besiege*): 5 to 8 oz/A; PHI 14d, REI 24h, Bee: H, Groups 28 & 3A.

deltamethrin (Delta Gold*): 1 to 2.4 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.

esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A; PHI 7d, REI 12h, Bee: H, Group 3A.

gamma-cyhalothrin (Declare*): 0.77 to 1.28 oz/A; PHI 7d, REI 24h, Bee: H, Group 3A.

lambda-cyhalothrin (Warrior* II): 0.96 to 1.6 oz/A; PHI 7d, REI 24h, Bee: H, Group 3A.

methomyl (Lannate* LV): 1.5 pt/A; PHI 6d, REI 48h, Bee: H, Group 1A. Variegated cutworm only.

permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A; PHI 14d, REI 12h, Bee: H, Group 3A.

spinosad (SeduceOG): 20 to 44 lb/A or 0.5 to1 lb/1000 sq ft.; PHI 7d, REI 4h, Bee: M, Group 5. Spread bait on soil around plants.

zeta-cypermethrin (Mustang*): 1.28 to 4 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.  

European Corn Borer (Ostrinia nubilalis)

Larvae infest potato stems but rarely cause yield reductions; however, larval infestations can exacerbate drought stress. Higher levels of stem infestations have been associated with a higher incidence of blackleg. For more information on ECB, see the Sweet Corn section. 

acetamiprid (Assail 30SG): 2.5 to 4 oz/A; PHI 7d, REI 12h, Bee: M, Group 4A. For use as an ovicide only.

alpha-cypermethrin (Fastac* EC): 1.8 to 3.8 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

beta-cyfluthrin (Baythroid* XL): 1.6 to 2.8 oz/A; PHI 0d, REI 12h, Bee: H, Group 3A.

Burkholderia spp. strain A396 (Venerate XCOG): 1 to 4 qt/A; PHI 0d, REI 4h, Bee: M. Group UN.

chlorantraniliprole (Coragen): 3.5 to 7.5 oz/A; PHI 14d, REI 4h, Bee: L, Group 28. Apply as a foliar spray.

chlorantraniliprole & lambda-cyhalothrin (Besiege*): 6 to 9 oz/A; PHI 14d, REI 24h, Bee: H, Groups 28 & 3A.

Chromobacterium subtsugae strain PRAA4-1 (GrandevoOG): 1 to 3 lb/A; PHI 0d, REI 4h, Bee: M. Group UN.

cyantraniliprole (Verimark): 10 to 13.5 oz/A for soil applications, 0.46 to 0.75 oz/100 lb of seed-pieces; PHI 0d, REI 4h, Bee: H, Group 28. For soil applications at planting and potato seed-piece treatment.

deltamethrin (Delta Gold*): 1.5 to 2.4 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.

esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A; PHI 7d, REI 12h, Bee: H, Group 3A.

gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 7d, REI 24h, Bee: H, Group 3A.

indoxacarb (Avaunt): 3.5 to 6 oz/A; PHI 7d, REI 12h, Bee: H, Group 22.

lambda-cyhalothrin (Warrior* II): 1.28 to 1.92  oz/A; PHI 7d, REI 24h, Bee: H, Group 3A.

novaluron (Rimon 0.83EC): 6 to 12 oz/A; PHI 14d, REI 12h, Bee: L, Group 16B. Most effective on 1st and 2nd instars.

permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A; PHI 14d, REI 12h, Bee: H, Group 3A.

pyrethrin (PyGanic EC5.0OG): 4.5 to 17 oz/A; 0.25 to 0.50 oz/gal, 3 gal/1000 sq ft in greenhouse for backpack sprayers; PHI 0d, REI 12h, Bee: M, Group 3A.

spinetoram (Radiant SC): 6 to 8 oz/A; PHI 7d, REI 4h, Bee: M, Group 5.

spinosad (Entrust SCOG): 3 to 10 oz/A; PHI 7d, REI 4h, Bee: M, Group 5.

zeta-cypermethrin (Mustang*): 1.76 to 4 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

Flea Beetles, Potato (Epitrix cucumeris) and Eggplant (E. fuscula)

Shiny black beetles less than 1/8" long. Adults spend the winter under plant residue along tree lines or in the field. In the early spring, they feed on solanaceous weeds until they move to potato or other solanaceous crops. Numerous tiny feeding shot holes can injure leaves and stunt young plants. Management practices include clean cultivation, crop rotation, delayed plantings, removing or avoiding spring weed hosts, use of row covers, and applying spot treatments targeting young potato plants along the field edges. Full-size plants rarely require treatment for flea beetles. Most insecticides registered to control CPB, including spinosad, will control FB. Sweep young plants 25 times and spot treat potatoes along field edges if 50 beetles are found in the sweep net.

acetamiprid (Assail 30SG): 1.5 to 2.5 oz/A; PHI 7d, REI 12h, Bee: M, Group 4A.

alpha-cypermethrin (Fastac* EC): 1.8 to 3.8 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

beta-cyfluthrin (Baythroid* XL): 1.6 to 2.8 oz/A; PHI 0d, REI 12h, Bee: H, Group 3A.

bifenthrin (Brigade* 2EC): 3.2 to 9.6 oz/A at cultivation or lay-by, 2.1 to 6.4 oz/A foliar; PHI 21d, REI 12h, Bee: H, Group 3A. Sweet potato and black flea beetles only. Apply as foliar spray to control adults only.

carbaryl (Sevin XLR Plus): 0.5 to 1 qt/A; PHI 7d, REI 12h, Bee: H, Group 1A.

chlorantraniliprole & lambda-cyhalothrin (Besiege*): 6 to 9 oz/A; PHI 14d, REI 24h, Bee: H, Groups 28 & 3A.

clothianidin (Belay): 2 to 3 oz/A for foliar application, 9 to 12 oz/A for soil application, 0.4 to 0.6 oz/100 lbs seed for seed-piece application; PHI 14d, REI 12h, Bee: H, Group 4A. Do not apply treatment between 50% row closure and petal fall. Soil application may be at planting or as a sidedress at ground-crack during hilling (cover with at least 3" of soil).

cyantraniliprole (Verimark): 10 to 13.5 oz/A for soil applications at planting, 0.46 to 0.75 oz/100 lb seed-pieces; PHI 0d, REI 4h, Bee: H, Group 28. For soil applications at planting and potato seed-piece treatment. Suppression of potato flea beetle only. 

deltamethrin (Delta Gold*): 1.5 to 2.4 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.

dinotefuran (Venom): 0.3 lb/A foliar or 1.4 to 1.65 lbs/A soil; PHI 7d foliar, REI 12h, Bee: H, Group 4A. Soil application may be applied as a narrow band before planting, in-furrow at planting, or as a sidedress at ground-crack during hilling and immediately covered with soil.

esfenvalerate (Asana* XL): 5.8 to 9.6 oz/A; PHI 7d, REI 12h, Bee: H, Group 3A. Apply when temperature is less than 80°F and when foliage is free from dew or other moisture.

gamma-cyhalothrin (Declare*): 1.02 to 1.54 oz/A; PHI 7d, REI 24h, Bee: H, Group 3A. Adults only. 

imidacloprid (Admire Pro): 1.3 oz/A for foliar application, 5.7 to 8.7 oz/A for soil application; PHI 7d foliar, 125d soil, REI 12h, Bee: H, Group 4A.

imidacloprid + mancozeb (TOPS-MZ-Gaucho): 0.75 lb/100 lb seed-pieces; REI 24h, Bee: H, Group 4A. Seed-piece treatment only. Do not make subsequent application of another neonicotinoid (Group 4A) insecticide following a seed-piece treatment. Aids in control of aphids. Not registered in CT or VT.

kaolin (Surround WPOG): 25 to 50 lb/A or 0.25 to 0.5 lb/gal; PHI 0d, REI 4h, Bee: L. Suppression/repellence only. Generally compatible as a tank mix with other insecticides.

lambda-cyhalothrin (Warrior* II): 1.28 to 1.92  oz/A; PHI 7d, REI 24h, Bee: H, Group 3A. Adults only. 

methomyl (Lannate* LV): 1.5 pt/A; PHI 6d, REI 48h, Bee: H, Group 1A.

oxamyl (Vydate* C-LV): 17 to 34 oz/A; PHI 7d, REI 48h, Bee: H, Group 1A. NOTE: Vydate L is NOT labeled for potatoes.

permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A; PHI 14d, REI 12h, Bee: H, Group 3A.

phorate (Thimet* 20G): 8.5 to 11.3 oz/1000 row ft for light or sandy soils, 13 to 17.3 oz/1000 row ft in heavy or clay soils; PHI 90d, REI 48h, Bee: H, Group 1B. May only be applied at planting in sandy or clay soils. Distribute granules in-furrow or band on each side of the row and incorporate. Granules must be incorporated into soil. For control of larvae and reduction of adults.

pyrethrin (PyGanic EC5.0OG): 4.5 to 17 oz/A; 0.25 to 0.50 oz/gal, 3 gal/1000 sq ft in greenhouse for backpack sprayers; PHI 0d, REI 12h, Bee: M, Group 3A.

thiamethoxam (Actara): 1.5 to 3 oz/A; PHI 14d, REI 12h, Bee: H, Group 4.

thiamethoxam (Cruiser 5FS): 0.11 to 0.16 fl. oz/100 lb of seed; REI 12h, Bee: H, Group 4A. See rates based on row spacing on label. Systemic seed treatment. Use only approved equipment for applying liquid seed treatment products to potatoes. See label for rates based on row spacing. For early-season protection.

thiamethoxam (Platinum): 5 to 8 oz/A; REI 12h, Bee: H, Group 4. Systemic insecticide applied to seed pieces in-furrow during planting, impregnated on dry granular fertilizer, or as directed spray at plant emergence or during last hilling operation. Must incorporate into root zone with sufficient irrigation within 24 hours. DO NOT apply as a foliar spray.

zeta-cypermethrin (Mustang*): 1.76 to 4 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.  

Potato Leafhopper (Empoasca fabae)

Potato leafhoppers overwinter in Louisiana and vicinity and move north on storm fronts into the central states and then into New England on winds from the west. Low levels of leafhopper feeding can severely damage plants and cause symptoms known as hopper burn. Leaves yellow, turn brown and die. Adults are light green, 1/8" long, and wedge-shaped, while nymphs are bright green, flatter and fatter than adults, and move sideways in a crab-like fashion. Sample with sweep net, or shake plants to see if adults fly up, and treat if more than 1 adult per sweep is found. Nymphs can be monitored by visually inspecting lower leaf surfaces on lower leaves. Treat if more than 15 nymphs are found per 50 leaves.

acetamiprid (Assail 30SG): 1.5 to 4 oz/A; PHI 7d, REI 12h, Bee: M, Group 4A.

alpha-cypermethrin (Fastac* EC): 1.8 to 3.8 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

azadirachtin (Azatin OOG): 4 to 16 oz/A foliar or drench, 4 to 16 oz/100 gal in greenhouses; PHI 0d, REI 4h, Bee: L, Group UN. When using lower rates, combine with adjuvant for improved spray coverage and translaminar uptake. For suppression of nymphs only.

beta-cyfluthrin (Baythroid* XL): 0.8 to 1.6 oz/A; PHI 0d, REI 12h, Bee: H, Group 3A.

carbaryl (Sevin XLR Plus): 0.5 to 1 qt/A; PHI 7d, REI 12h, Bee: H, Group 1A.

chlorantraniliprole & lambda-cyhalothrin (Besiege*): 5 to 8 oz/A; PHI 14d, REI 24h, Bee: H, Groups 28 & 3A.

Chromobacterium subtsugae strain PRAA4-1 (GrandevoOG): 2 to 3 lb/A; PHI 0d, REI 4h, Bee: M, Group UN.

clothianidin (Belay): 2 to 3 oz/A for foliar application, 9 to 12 oz/A for soil application, 0.4 to 0.6 oz/100 lb seed for seed-piece application; PHI 14d, REI 12h, Bee: H, Group 4A. Do not apply treatment between 50% row closure and petal fall. Soil application may be at planting or as a sidedress at ground-crack during hilling (cover with at least 3" of soil).

deltamethrin (Delta Gold*): 1.5 to 2.4 oz/A; PHI 3d, REI 12h, Bee: H, Group 3A.

dimethoate (Dimethoate 4EC): 0.5 to 1 pt/A; PHI 0d, REI 48h, Bee: H, Group 1B.

dinotefuran (Venom): 0.3 lb/A foliar or 1.4 to 1.65 lbs/A soil; PHI 7d foliar, REI 12h, Bee: H, Group 4A. Soil application may be applied as a narrow band before planting, in-furrow at planting, or as a sidedress at ground-crack during hilling and immediately covered with soil.

esfenvalerate (Asana * XL): 5.8 to 9.6 oz/A; PHI 7d, REI 12h, Bee: H, Group 3A.

fenpyroximate (Portal XLO): 2 pt/A; PHI 7d, REI 12h, Bee: L, Group 21A.

flupyradifurone (Sivanto): 7 to 14 oz/A; PHI 7d, REI 4h, Bee: L, Group 4D.

gamma-cyhalothrin (Declare*): 0.77 to 1.28 oz/A; PHI 7d, REI 24h, Bee: H, Group 3A.

imidacloprid (Admire Pro): 1.3 oz/A for foliar application, 5.7 to 8.7 oz/A for soil application; PHI 7d foliar, 125d soil, REI 12h, Bee: H, Group 4A.

imidacloprid + mancozeb (TOPS-MZ-Gaucho): 0.75 lb/100 lb seed-pieces; REI 24h, Bee: H, Group 4A. Seed-piece treatment only. Do not make subsequent application of another neonicotinoid (Group 4A) insecticide following a seed-piece treatment. Aids in control of aphids. Not registered in CT or VT.

insecticidal soap (M-PedeOG): 1.25 to 2.5 oz/gal water; PHI 0d, REI 12h, Bee: L. Spray to wet all infested plant surfaces. May need to make repeated applications. For enhanced and residual control, apply with companion labeled insecticide.

kaolin (Surround WPOG): 25 to 50 lb/A or 0.25 to 0.5 lb/gal; PHI 0d, REI 4h, Bee: L. Suppression/repellence only. Generally compatible as a tank mix with other insecticides.

lambda-cyhalothrin (Warrior* II): 0.96 to 1.6 oz/A; PHI 7d, REI 24h, Bee: H, Group 3A.

malathion (Malathion 57EC): 1 to 1.5 pt/A; PHI 0d, REI 12h, Bee: H, Group 1B.

methomyl (Lannate* LV): 1.5 to 3 pt/A; PHI 6d, REI 48h, Bee: H, Group 1A.

oxamyl (Vydate* C-LV): 17 to 34 oz/A; PHI 7d, REI 48h, Bee: H, Group 1A. NOTE: Vydate L is NOT labeled for potatoes.

paraffinic oil (Organic JMS Stylet-OilOG): 3 to 6 qt/100 gal water; PHI 0d, REI 4h, Bee: L.

permethrin (Pounce* 25WP): 6.4 to 12.8 oz/A; PHI 14d, REI 12h, Bee: H, Group 3A.

phorate (Thimet* 20G): 8.5 to 11.3 oz/1000 row ft for light or sandy soils, 13 to 17.3 oz/1000 row ft in heavy or clay soils; PHI 90d, REI 48h, Bee: H, Group 1B. May be applied at planting in sandy or clay soils. Distribute granules in-furrow or band on each side of the row and incorporate. Granules must be incorporated into soil. May be applied post-emergence on sandy soils only. Place granules on each side of hill at seed-piece level before hilling, 4 to 6 weeks after planting.

pyrethrin (PyGanic EC5.0OG): 4.5 to 17 oz/A; 0.25 to 0.50 oz/gal, 3 gal/1000 sq ft in greenhouse for backpack sprayers; PHI 0d, REI 12h, Bee: M, Group 3A.

sodium tetraborohydrate decahydrate (Prev-AM): 100 oz/100 gal; REI 12h, Bee: L, Group 25. Do not apply in midday sun or mix with copper, sulfur or oils.

sulfoxaflor (Transform WG): 1.5 to 2.25 oz/A; PHI 7d, REI 24h, Bees: H, Group 4C. Do not apply between 3 days prior to bloom and until after petal fall. 

thiamethoxam (Actara): 1.5 to 3 oz/A; PHI 14d, REI 12h, Bee: H, Group 4.

thiamethoxam (Cruiser 5FS): 0.11 to 0.16 fl. oz/100 lb of seed; REI 12h, Bee: H, Group 4A. See rates based on row spacing on label. Systemic seed treatment. Use only approved equipment for applying liquid seed treatment products to potatoes. See label for rates based on row spacing. For early-season protection.

thiamethoxam (Platinum): 5 to 8 oz/A; PHI 30d, REI 12h, Bee: H, Group 4. Systemic insecticide applied to seed pieces in-furrow during planting, impregnated on dry granular fertilizer, or as directed spray at plant emergence or during last hilling operation. Must incorporate into root zone with sufficient irrigation within 24 hours. DO NOT apply as a foliar spray.

zeta-cypermethrin (Mustang*): 3.2 to 4 oz/A; PHI 1d, REI 12h, Bee: H, Group 3A.

Wireworms, including corn wireworm (Melanotus communis)

Corn wireworm is reported to be the most common wireworm species in the Northeast, but others may also be present including the tobacco wireworm, (Conodoerus verspertinus). Corn wireworm causes damage to vegetable crops including cabbage, corn, lettuce, pepper, potato and sweet potato as well as field crops including field corn, sorghum, soybean, tobacco, and wheat. Wireworms are attracted to germinating seeds and can be a seed pest in large-seeded crops such as beans, peas and corn.

Wireworms are the underground larval stage of click beetles, which are elongated, brown beetles that snap their bodies to make a clicking sound. Adults emerge from the soil in May and June and tend to hide during the day and fly mostly at night.  Egg-laying females prefer grassy or weedy fields. Eggs are deposited in the soil, often in batches. Larvae are slender, yellow-brown, hard-shelled, and shiny, with 3 pairs of legs. Wireworms spend multiple years in the soil, and completing their development from egg to adult may take 2 to 5 years depending on conditions. They feed on other insects, roots, seeds, tubers, and other plant tissue. Wireworms prefer wet soils and moderate temperatures (at least 70º F); they migrate up to reach warmer soils, but down to avoid excessive cold, heat, or drought. In agricultural fields, where other plants are eliminated, the crop itself is the primary available food source. Wireworms may injure potatoes by feeding on the seed piece resulting in weak stands, but the majority of their damage is caused by tunneling into tubers which reduces yield quality. Wireworm tunnels also provide entry to tuber pathogens, increasing tuber rots.

Tuber damage may be worse under drought conditions, where the crop provides the only source of moisture in a dry field. Wireworms are more pronounced in soils that are wet, heavy or high in organic matter. They may be worse in low areas of the field; however, they will move away from saturated soils that lack oxygen. Wireworm problems occur most often in fields that were recently in hay, pasture or sod (within the past 3 years), had grassy weeds in previous years, or were in sorghum-sudangrass or grass cover crops, or cereal grains.  Forest soils may also harbor wireworms, thus recently cleared land can be infested. The most important method of wireworm control is to avoid planting potatoes or other susceptible crops in these fields.

Baits using corn or wheat or rolled oats placed 6" to 8" deep can be used to determine if wireworms are present, but these sampling methods are labor intensive, and potatoes are often planted in cold soils before such samples could be completed.  A review of many insecticide trials over 2 decades indicated that organophosphate insecticides applied as a preplant broadcast or in-furrow gave better control than carbamates, and that fipronil and bifrenthrin were as effective as the organophosphates, but with less environmental impact and potential human safety concerns.

bifenthrin (Brigade* 2EC): 9.6 to 19.2 oz/A at planting for corn and tobacco wireworm only, 3.2 to 9.6 oz/A at cultivation or lay-by, 2.1 to 6.4 oz/A foliar for southern potato wireworm only; PHI 21d, REI 12h, Bee: H, Group 3A. May be applied as soil-incorporated broadcast, bed, or t-band spray into planting furrow or soil-directed and incorporated spray at cultivation or lay-by for wireworms. May be applied as foliar spray for click beetle (adult wireworm).

Burkholderia spp. strain A396 (MajesteneOG): 4 to 16 qt/A at planting OR 1 to 16 fl oz/100 lb seed-pieces for seed treatment; PHI 0d, REI 4h, Bee: M, Group UN. Suppression only. 

ethoprop (Mocap* 15G): 1.4 lb/1000 row feet banded, 27 to 40 lb/A broadcast; REI 48h, Bee: H, Group 1B. Apply before potato emergence only. Direct contact with seed-pieces may contribute to delayed emergence. Extremely toxic to birds. Do not leave granules on soil surface. Apply only once during the growing season.

fipronil* (Regent 4SC): 3.2 oz/A; PHI 90d, REI 0d, Bee: H, Group 2. Make one in-furrow treatment at planting. Must be thoroughly incorporated and covered with soil immediately after application. DO NOT use as T-band over the top of closed furrow.

imidacloprid + mancozeb (TOPS-MZ-Gaucho): 0.75 lb/100 lb seed-pieces; REI 24h, Bee: H, Group 4A. Seed-piece treatment only. Do not make subsequent application of another neonicotinoid (Group 4A) insecticide following a seed-piece treatment. Aids in control of aphids. Not registered in CT or VT. Suppression only.

Isaria fumosorosea Apopka Strain 97 (PFR-97 20% WDGOG): 1 to 2 lb/A soil drench; PHI 0d, REI 4h, Bee: M, Group UN.

phorate (Thimet* 20G): 8.5 to 11.3 oz/1000 row ft for light or sandy soils, 13 to 17.3 oz/1000 row ft in heavy or clay soils; PHI 90d, REI 48h, Bee: H, Group 1B. May be applied at planting in sandy or clay soils. Distribute granules in-furrow or band on each side of the row and incorporate. Granules must be incorporated into soil. May be applied post-emergence for suppression only of wireworms on sandy soils only. Place granules on each side of hill at seed-piece level before hilling, 4 to 6 weeks after planting.

thiamethoxam (Cruiser 5FS): 0.11 to 0.16 fl. oz/100 lb of seed; REI 12h, Bee: H, Group 4A. See label for rates based on row spacing. Systemic seed treatment. Use only approved equipment for applying liquid seed treatment products to potatoes. For protection of seed-pieces from wireworm.

thiamethoxam (Platinum): 5 to 8 oz/A; REI 12h, Bee: H, Group 4. Systemic insecticide applied to seed pieces in-furrow during planting, impregnated on dry granular fertilizer before or at planting, or as directed spray at plant emergence or during last hilling operation. Must incorporate into root zone with sufficient irrigation within 24 hours. DO NOT apply as a foliar spray. For seed-piece protection only.

Weed Control

NOTE:  For the herbicides listed below, one product trade name and formulation is provided for each active ingredient along with preharvest interval (PHI), restricted entry interval (REI), resistance management group number, and example of rates and special instructions. In many cases, there are other products available with the same active ingredient. However, not all products with the same active ingredient are registered for use in a crop. Always check the product label to be sure that the crop is listed before using. 

A common strategy of potato growers is to combine one of the "grass" herbicides listed (EPTC, metolachlor or pendimethalin) with one of the broadleaf herbicides listed below (linuron or metribuzin). In more northern areas of New England, grasses are much less of a problem due to cooler soil temperatures, and there are many cases where only a broadleaf herbicide is necessary. If only a broadleaf herbicide is used, sethoxydim (Poast), described below, could be used during the growing season to provide emergency or spot treatment of any emerged annual or perennial grasses that were not anticipated.

Yellow Nutsedge: The herbicides that will provide the best control of yellow nutsedge, include a soil-incorporated treatment of EPTC (Eptam), a preemergence application of metolachlor (Dual) or a postemergence application of Metribuzin. The best strategy is to map the problem spots in a field and make an application of either Eptam or Dual before the nutsedge emerges. A postemergence application of Metribuzin can be used to clean any areas that escape the Eptam or Dual treatment. The best time to apply a postemergence treatment of Metribuzin is when the yellow nutsedge is 4-6" tall. Remember that nutsedge is not a grass and will not be controlled by grass herbicides like Poast and Select Max.

Quackgrass: The best strategy for quackgrass control is an application of glyphosate (Roundup) to actively growing quackgrass in the fall prior to planting. An application of Roundup in the spring at least 3 days prior to soil preparation will suppress quackgrass but will not kill it. EPTC (Eptam) and sethoxydim (Poast) can also be used to suppress quackgrass during the growing season. Both of these herbicides will provide greater activity if the quackgrass rhizomes (underground storage roots) are cut thoroughly with a disc prior to planting the potatoes. Also, Poast will provide better suppression of quackgrass if the lower rate is used and repeated when the quackgrass regrows (about 2 weeks after the first application). Be sure to observe the preharvest interval for both Eptam and Poast.

Stale Seedbed

See Stale Seedbed Technique for information on the use of these herbicides or flaming.

  • carfentrazone (Aim EC): PHI 0d, REI 12h, Group 14.
  • glyphosate (Roundup Power Max): PHI 14d, REI 4h, Group 9.
  • paraquat (Gramoxone SL 2.0*): restricted use. REI 12h or 24h, Group 22.
  • pelargonic acid (Scythe): PHI 1d, REI 12h, Group 0.

Preemergent Herbicides (before weeds germinate)

dimethenamid (Outlook)PHI 40d, REI 12h, Group 15. Apply 12-21 oz/A per application, only 1 application per year. Can be applied after planting or after drag-off.  Rate based on soil texture and organic matter content. Use the lower rate on sandy soils and the higher rate on silt and clay soils. In cold and wet growing conditions, Outlook application may result in delayed emergence or early season stunting.

EPTC (Eptam 7E)PHI 30d, REI 12h, Group 15. Apply and 3.5-9 pt/A per application, multiple applications allowed per year. Do not exceed 14 pt/A per season. Can be applied to the soil surface before planting and immediately incorporated 2-3” into the soil, or as a band where beds will be formed and then covered with 3-4” of soil. Can also be applied after planting but before potatoes emerge, immediately after drag-off, at laby-by, or after a clean cultivation. Incorporate immediately on a wet soil surface or within 36 hours on a dry soil surface. Care should be taken not to fold in the band treatment. Rate based on soil texture, application timing, and weed composition. ‘Superior’ potatoes are sensitive to Eptam and, early season stunting may occur under stress conditions.

ethalfluralin (Sonalan HFP)REI 24h, Group 3. Apply 1.33-2.67 pts/A per application. Do not exceed 2.67 pts/A per year. Apply broadcast, immediately after planting but prior to crop emergence. Rate based on soil texture. Must be incorporated for maximum effectiveness. Incorporate 0.5-1” into the soil with water through irrigation or rainfall within 2 days of application. Or mechanically incorporate 2-3” into the soil. Ensure incorporation equipment does not damage seed pieces or unemereged shoots, or expose untreated soil.

fomesafen (Reflex)PHI 70d, REI 24h, Group 14. Apply 1 pt/A per application, only 1 application every other year. Can be applied as a broadcast application after planting but before potato emergence. Take care not to expose untreated soil. Has not been tested on all varieties, crop tolerance should be verified before treating the entire field. Do not apply to emerged potato plants or severe crop injury will occur.

linuron (Lorox DF)REI 24h or 8d, Group 5. Apply 1.5-3 lbs/A per application, only 1 application per year. Rate is based on soil texture and weed composition. Apply after planting but prior to crop emergence. If beds are to be dragged and/or hilled, apply after the final dragging or hilling operation.  Do not spray over top of emerged potatoes. Plant seeds at least 2" deep. Apply before grasses are 2” tall and before broadleaf weeds are 6” tall, preferably just before or when weed seedlings emerge. If emerged weeds are present, add 1 pt surfactant for each 25 gal of spray mixture.  Application should be made to moist soil, followed by 1-2” of water through irrigation or rainfall within 2 weeks of application.

sulfentrazone (Aquesta 4F): REI 12h, Group 14. Apply 3-8 oz/A per application, only 1 application allowed per year. Rate based on soil texture, organic matter and soil pH. Apply after planting and dragoff but before potatoes emerge, with a minimum of 10 gal/A of spray. Incorporate into the soil with water through irrigation or rainfall. If dry conditions persist within 7 days of application, incorporate no more than 2” into the soil to activate. Undesirable crop injury can result from irrigation with alkaline water of 7.5 pH or greater. You can increase the amount of available sulfentrazone in the soil by irrigating with highly alkaline water. Young or stressed crops and some varieties including Sangre, Shepody, and Snowden planted on coarse soil are susceptible to adverse effects. Has not been tested on all varieties, crop tolerance should be verified before treating the entire field. Do not use on soils that contain less than 1% organic matter. Do not apply to emerged potatoes.

Pre- and Postemergent Herbicides

metribuzin (Metribuzin 75)PHI 60d, REI 12h, Group 5. Apply 0.3-0.6 lb/A per application, up to 2 applications allowed per year. This product may be applied once before and once after crop emergence. Do not exceed 1.3 lb/A per season. Can be applied after planting or immediately after drag-off but before crop emerges. Do not incorporate into the soil. Can also apply over the tops of potato plants, but not prior to rainfall or irrigation, on recently cultivated potatoes, or within 3 days after periods of cool wet weather. Apply with 20 gal/A of spray.

Only make postemergence applications on russet or white skinned potatoes that are not early maturing, Early maturing smooth-skinned white and all red skinned varieties may be injured with applications after crop emergence. The varieties Atlantic, Bellchip, Centennial, Chipbelle and Shepody are sensitive to Metribuzin. Applications before crop emergence on these varieties may cause crop injury under adverse weather conditions, on coarse soils, under high soil pH, with high application rates, or with mechanical incorporation. May cause some chlorosis or minor necrosis. Crop tolerance should be verified before treating the entire field.

pendimethalin (Prowl H2O)REI 24h, Group 3. Apply 1.5-3 pt/A per application, only 1 application per year. Rate based on soil texture and weed composition. Apply as a broadcast spray after planting or drag-off but before potatoes emerge. Do not apply to the variety White Rose. If rainfall does not occur within 7 days after application, incorporate 1-2" into the soil with shallow cultivation. Be careful not to damage seed pieces when incorporating. Can also be applied from crop emergence to the 6” growth stage. Do not apply after emergence if potatoes are under stress from cold/wet or hot/dry conditions or crop injury may occur.

s-metolachlor (Dual Magnum)PHI 60d for applications at planting to drag-off, 40d for applications at lay-by, REI 12h, Group 15. Apply 1.0-2.0 pt/A per application. This product may be applied once before and once after crop emergence. Do not exceed 3.6 pt/A per year. Can be applied before planting or after plating but before potatoes have emerged. If applying before planting, mechanically incorporate 3” into the soil. If applying after planting, you can incorporate 2” into the soil but take care not to damage seed pieces. Can also be applied after potatoes have emerged after hilling/lay-by at 1.67 pt/A.

trifluralin (Treflan HFP)REI 12h, Group 3. Apply 1-2 pt/A per application, only 1 application per year. Can be applied after planting either before potatoes emerge, immediately following dragoff, or after potato plants have fully emerged. Rate based on soil texture and variety.  Set incorporation equipment so that the bed and furrow will be uniformly covered with a layer of treated soil. If the layer of treated soil is not uniform and the herbicide is concentrated over the bed, potato emergence may be delayed and stem brittleness can occur. When applying and incorporating Treflan HFP after potato plants have fully emerged, do not completely cover the foliage with treated soil.

rimsulfuron (Matrix SG)PHI 60d or 30d*, REI 4 hr, Group 2. Apply 1-1.5 oz/A per application, up to 2 application allowed per year, a minimum of 14 days apart. Do not exceed 2.5 oz/A per year. Can be applied after hilling, drag-off, or reservoir tillage, to a clean, newly prepared seedbed. Activate and incorporate 2-3” into the soil with 0.33-1" of water through irrigation or rainfall within 5 days of application. Can also be applied after crop emergence, when weeds are less than 1" tall or 1” in diameter. Activate with 0.33-1" of water through irrigation or rainfall no sooner than 4 hours, but not more than 5 days after application. Weed control may be less consistent in cold, dry conditions. *Some rimsulfuron products have a 60d PHI while others have a 30d PHI. Read label carefully and use correct interval for the product you are using.

Postemergent Herbicides (after weeds germinate)

carfentrazone (Aim EC)PHI 7d, REI 12h, Group 14. Apply 0.5-2 oz/A per application, multiple applications allowed per year. Do not exceed 11.6 oz/A per season. Can be applied as a preplant burndown no later than 1 days after planting by seed. Can also be applied to row middles of emerged crops with hooded sprayers to control emerged weeds. Prevent any spray from contacting the crop, or injury will occur.  For best results, make application to actively growing weeds up to 4” tall and rosettes less than 3” across. Can use up to 5.8 fl oz/A as a harvest aid. Adequate desiccation is achieved within 14 days after application.

clethodim (Select Max)PHI 30d, 24hr REI, Group 1. Apply 6-32 oz/A per application, up to 2 applications per year, a minimum of 14 days apart. Do not exceed 64 oz/A per year.  Apply to actively growing grasses. Add 0.25% v:v nonionic surfactant (1 qt/100 gal of spray).  Can also be applied as a spot-spray by mixing 0.33-0.66% (0.44-0.85 oz/gal) Select Max and 0.25% v:v nonionic surfactant (0.33 oz/gal).  Spray to wet, but do not allow runoff of spray solution.

diquat (Reglone): PHI 7d, REI 24h, Group 22. Apply 1-2 pt/A per application, up to 2 applications allowed per year, a minimum of 5 days apart. Do not exceed 4 pt/A per year. For use as a preharvest desiccant. Do not apply to drought-stressed potatoes. Apply in a minimum of 20 gal/A of spray.

glyphosate (Roundup PowerMax): PHI 14d, REI 4h, Group 9. Apply 10 oz to 3.1 qts/A per application, multiple applications allowed per year. Do not exceed 5 qts/A per year. Rate based on target weed species. Can be applied during fallow intervals, prior to planting or transplanting, at planting, or before crop has emerged. Could cause injury when applied prior to transplanting or direct-seeding into plastic mulch. Remove residual product from plastic mulch with a 0.5” of water through irrigation or rainfall prior to planting.

paraquat (Gramoxone SL 3.0): REI 12h or 24h (application type), Group 22. Apply 0.7-1.3 pts/A per application. Up to 3 applications allowed per year, a minimum of 7 days apart. Do not exceed 4 pts/A per year. Can be applied before, during, or after planting, but before emergence (up until ground cracking) as a banded or broadcast application in a minimum of 10 gal/A of spray. May be fatal if swallowed or inhaled. Applicators must complete an EPA-approved paraquat training listed on the following website https://www.epa.gov/pesticide-worker-safety/paraquat-dichloride-training...(link is external). The training must be completed a minimum of every three years.

pelargonic acid (Scythe): PHI 1d, REI 12h, Group 0. Apply a 3-10% solution (3-10 gallons per 100 gallons of spray). Rate based on target weed species. Apply in 75-200 gal/A of spray or with a spot sprayer until foliage is wet but not to the point of runoff. Repeat applications as necessary. Can apply for vegetative burndown during site preparation, prior to crop emergence from soil, as a directed and shielded spray during crop growth taking care to avoid contact with foliage and green tissue of crops, or after harvest. For beets, can also apply as a harvest aid to remove crop leaves.

sethoxydim (Poast)PHI 30d, REI 12h, Group 1. Apply up to 2.5 pt/A per application, multiple applications are allowed, a minimum of 14 days between applications. Do not exceed 5 pts/A per year. Apply to actively growing grasses. Use with crop oil concentrate (2 pt/A) or methylated seed oil (1.5 pt/A). Note that crop oil can cause injury under hot and humid conditions. Can also be applied as a spot-spray by mixing 1-1.5% (1.3-1.9 oz/gal) Poast and 1% v:v crop oil concentrate (1.3 oz/gal). Spray to wet, but do not allow runoff of spray solution.