Disease Control : New England Vegetable Management Guide : UMass Amherst

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 26 and Fungicides and Bactericides Alphabetically Listed 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.

PESTICIDE USE IN GREENHOUSES AND HIGH TUNNELS:

Pesticides can be used on high tunnel and greenhouse crops if 1) the crop and pest/disease is on the label, AND the products specifically says it can be used in the greenhouse OR 2) the crop and pest/disease is on the label, AND the product is ‘silent’ about use in the greenhouse in the greenhouse. Products that specifically prohibit greenhouse use cannot be used in greenhouses or high tunnels regardless of the crops or pests/diseases listed on the label.

Cladosporium Leaf Spot (Cladosporium variabile)

Cladosporium leaf spot, caused by Cladosporium variabile, was previously considered to be of minor importance in spinach crops but can be severe in spinach seed production and has become a common problem in winter high tunnel production. Symptoms begin on the foliage as pale/tan lesions that develop olive-green spores. The most conducive environment for disease development is cool and moist with temperatures between 59-68ºF and relative humidity above 80%. However, the fungus can grow under a wide range of temperatures, ranging from 41-86ºF. The epidemiology of this disease is not well-known. Spinach seeds carry the fungus, but it has not been determined whether the disease is transmitted via contaminated seed to soil or seedlings. It is also not known how long the fungus can survive on spinach residues in soil or in weed hosts. C. variabile has been recovered from dried leaves and seed stocks up to 8 years old. Cultural controls rely mainly on sanitation—the removal of infected plants, spinach debris, spinach volunteers, and unused seed. Start with certified, disease-free seed or treat seed with hot water or bleach to reduce seedborne inoculum. Avoid covering wet plants with row covers. Cultivar susceptibility varies but is rarely reported by seed producers or distributors.

Bacillus mycoides isolate J (LifeGard WG^OG): 1.0 to 4.5 oz/A; PHI 0d, REI 4h, Group P06. Apply at first true leaf stage or after thinning. Refer to label for other appropriate rates and application volumes.

Downy Mildew (Peronospora farinosa)

Spinach downy mildew (SDM) is considered the most important disease of spinach and is favored by cool, moist conditions. The pathogen is host-specific to spinach and will not survive without a living host. Incidence of the disease appears to be increasing due to the increased use of high tunnels for winter spinach production. The potential overlap of field spinach and high tunnel spinach can create a “green bridge” for the disease, allowing the pathogen to transfer between fields and high tunnels. SDM begins as irregular yellow patches on upper leaf surfaces with purplish-gray sporulation on the undersides of leaves. Lesions may eventually dry out and turn brown. There are currently 19 numbered races of SDM, along with numerous "novel" races, and new races can emerge every year. SDM management relies on resistant cultivars, as well as managing relative humidity and leaf wetness. Select cultivars with resistance to races 1-19, if possible, and grow multiple cultivars that do not share the same gaps in resistance. Once infected, there is little that can be done to manage SDM. The pathogen can produce long-lived resting spores, called oospores, that can potentially survive in the soil without a living host. However, the role of oospores in season-to-season survival in New England is currently unknown. Rotate out of spinach for at least 2 years.

acibenzolar-S-methyl (Actigard 50WG): 0.5 to 0.75 oz/A; PHI 7d, REI 12h, Group P01. Do not apply to plants that are stressed or when extended cold or/and cloudy conditions are expected. May cause crop injury to young seedlings. See label for other restrictions.
ametoctradin plus dimethomorph (Zampro): 14.0 fl oz/A; PHI 0d, REI 12h, Groups 45 & 40. Do not apply to greenhouse or high tunnel crops.
azoxystrobin (Quadris F): 12.0 to 15.5 fl oz/A; PHI 0d, REI 4h, Group 11. Rotate with a non-Group 11 fungicide. Phytotoxicity may occur. Proceed when using tank mixes. See label for restrictions. Do not apply to greenhouse or high tunnel crops.
Bacillus amyloliquefaciens strain D747 (Double Nickel LC^OG): 1.0 to 6.0 qt/A; PHI 0d, REI 4h, Group BM02. Suppression only. See label for other application methods and rates.
copper hydroxide (Kocide 3000): 0.75 to 1.25 lb/A; PHI 0d, REI 48h, Group M01. Flecking may occur.
copper oxychloride plus copper hydroxide (Badge X2^OG): 0.75 to 1.25 lb/A; PHI 0d, REI 48h, Group M01. Flecking may occur. See label for precautions.
cyazofamid (Ranman 400SC): 2.75 fl oz/A; PHI 0d, REI 12h, Group 21.
cymoxanil (Curzate 60 DF): 5.0 oz/A; PHI 1d, REI 12h, Group 27. Use only in combination with a protectant fungicide.
famoxadone plus cymoxanil (Tanos): 8.0 to 10.0 oz/A; PHI 1d, REI 12h, Groups 11 & 27. Must be tank mixed with an appropriate contact fungicide from a different FRAC Group. Do not alternate or tank mix with other Group 11 fungicides.
fenamidone (Reason 500 SC): 5.5 to 8.2 fl oz/A; PHI 2d, REI 12h, Group 11. Do not apply to greenhouse or high tunnel crops.
fluopicolide (Presidio 4SC): 3.0 to 4.0 fl oz/A; PHI 2d, REI 12h, Group 43. Must be used in a tank mix with a fungicide with a different mode of action. Do not apply to greenhouse or high tunnel crops.
fluxapyroxad plus pyraclostrobin (Merivon Xemium): 6.0 to 11.0 fl oz/A; PHI 1d, REI 12h, Groups 7 & 11. Suppression only. Do not apply as tank mix with other pesticides or anything other than water. Do not apply to greenhouse or high tunnel crops.
fosetyl aluminum (Aliette WDG): 2.0 to 5.0 lb/A; PHI 3d, REI 24h, Group P07. Lower rate of 2-3lb/A may be used when tank mixed with another fungicide labeled for downy mildew (do not mix with copper). See label for instructions.
mandipropamid (Revus): 8.0 fl oz/A; PHI 1d, REI 4h, Group 40. Addition of adjuvant is recommended.
mefenoxam (Ridomil Gold SL): 0.25 pt/A; PHI 21d, REI 48h, Group 4. Must be applied pre- and post-plant for effective control of downy mildew. Incorporate into soil mechanically or with irrigation. See label for instructions and precautions. Do not apply to greenhouse or high tunnel crops.
oxathiapiprolin (Orondis Gold 200): 1.2 to 2.4 fl oz/A (foliar); PHI 0d, REI 4h, Groups 49. Do not apply to greenhouse or high tunnel crops.
oxathiapiprolin plus mandipropamid (Orondis Ultra): 5.5 to 8.0 fl oz/A; PHI 1d, REI 4h, Groups 49 & 40. Apply with an adjuvant.
phosphorous acid (Fosphite): 1.0 to 3.0 qt/20 gal foliar; PHI 0d, REI 4h, Group P07. Do not apply to plants that are heat- or moisture-stressed or recently treated with copper products.
pyraclostrobin (Cabrio EG): 12.0 to 16.0 oz/A; PHI 0d, REI 12h, Group 11. May cause leaf injury. Do not apply with anything other than water. See label for precautions. Do not apply to greenhouse or high tunnel crops.

Seed Decay

Buy treated seed. Do not use treated seed for food, feed, or oil purposes.

azoxystrobin(Dynasty): 0.10 to 0.38 fl oz/100 lb seed; REI 12h, Group 11. Not labeled for use in Maine.
fludioxonil (Maxim 4FS): 0.08 to 0.16 oz/100 lb seed; REI 12h, Group 12. For protection against seedborne and soilborne fungi. Does not control Pythium or Phytophthora.
mefenoxam (Apron XL): 0.085 to 0.64 fl oz/100 lb seed; REI 48h, Group 4. For Pythium damping-off protection. Do not use in greenhouse or enclosed environments. See label for restrictions.
thiram (Thiram 42-S): 8.0 lb/100 lb seed; REI 12h, Group M03.
Streptomyces sp. strain K61 (MycoStop^OG): 0.04 to 4.0 oz/lb seed; REI 4h, Group BM02. Other methods of application listed on label.

Stemphylium Leaf Spot (Stemphylium botryosum)

This relatively new disease of spinach was first detected in California in 2001. It affects both production spinach and spinach seed crops and has become a problem in high tunnel production. Details on the pathogen's life cycle are lacking, although the pathogen is known to be seedborne. In the field, the disease spreads slowly and damage is limited. Symptoms include light gray/tan leaf spots 1/16-1/2" in diameter, with larger spots being more irregular. As spots age they dry up and become papery in texture. Cultural controls rely mainly on sanitation—the removal of infected plants, spinach debris, spinach volunteers, and unused seed. Do not cover wet plants with row covers. Start with certified, disease-free seed or treat seed with hot water or bleach to reduce seedborne inoculum.

Bacillus mycoides isolate J (LifeGard WG^OG): 1.0 to 4.5 oz/100 gal water/A; PHI 0d, REI 4h, Group P06.
fludioxonil plus pydiflumetofen (Miravis Prime): 9.2 to 13.4 fl oz/A; PHI 0d, REI 12h, Groups 12 & 7.

White Rust (Albugo occidentalis)

White rust is a very damaging disease of spinach that is found only east of the Rocky Mountains in the U.S. Plant resistant cultivars and practice crop rotation. Apply preplant and foliar fungicides.

acibenzolar-S-methyl (Actigard 50WG): 0.5 to 0.75 oz/A; PHI 7d, REI 12, Group P01. Do not apply to plants that are stressed or when extended cold or/and cloudy conditions are expected. May cause crop injury to young seedlings. See label for other restrictions.
azoxystrobin (Quadris F): 6.0 to 15.5 fl oz/A; PHI 0d, REI 4h, Group 11. Quadris may be phytotoxic to spinach. See label for precautions. Do not apply to greenhouse or high tunnel crops.
copper hydroxide (Kocide 3000): 0.75 to 1.25 lb/A; PHI 0d, REI 48h, Group M01. Flecking may occur on spinach leaves.
copper oxychloride plus copper hydroxide (Badge X2^OG): 0.75 to 1.25 lb/A; PHI 0d, REI 48h, Group M01. Flecking may occur. See label for precautions.
cyazofamid (Ranman 400 SC): 2.75 fl oz/A; PHI 0d, REI 12h, Group 21.
famoxadone plus cymoxanil (Tanos): 8.0 to 10.0 oz/A; PHI 1d, REI 12h, Groups 11 & 27. Must be tank mixed with an appropriate contact fungicide from a different FRAC Group. Do not alternate or tank mix with other Group 11 fungicides.
fenamidone (Reason 500SC): 5.5 to 8.2 fl oz/A; PHI 2d, REI 12h, Group 11. Do not apply to greenhouse or high tunnel crops.
fluopicolide (Presidio 4SC): 3.0 to 4.0 fl oz/A; PHI 2d, REI 12h, Group 43. Must be used in a tank mix with a fungicide from a different FRAC Group. Do not apply to greenhouse or high tunnel crops.
laminarin (Vacciplant): 14.0 to 22.0 fl oz/A; PHI 0d, REI 4h, Group P04.
mefenoxam (Ridomil Gold SL): 0.25 pt/A; PHI 21d, REI 48h, Group 4. Must be applied pre- and post-plant for effective control of white rust. Incorporate into soil mechanically or with irrigation. See label for instructions and precautions. Do not apply to greenhouse or high tunnel crops.
pyraclostrobin (Cabrio EG): 8.0 to 12.0 oz/A. PHI 0d, REI 12h, Group 11. May cause crop injury under certain conditions. Do not apply as tank mix with anything other than water. See label for precautions. Do not apply to greenhouse or high tunnel crops.

Cucumber Mosaic Virus (CMV)

CMV is found worldwide and infects over 800 crop and weed hosts. Symptoms include mosaic, mottling, stunting, and leaf distortion. This disease is transmitted by aphids in a nonpersistent manner; insecticides are of no value in controlling this disease. Start with virus-free seed. Eliminate weeds such as chickweed, pokeweed, and milkweed. Grow resistant varieties such as Winter Bloomsdale and Renegade.

Disease Control