Disease Control

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. 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.

See also: Table 20: Fungicides and Bactericides Labeled for Vegetable Transplants.

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 widespread 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. 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 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.

FRAC Group P06:

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

Downy Mildew (Peronospora effusa formerly, P. farinosa f. sp. spinacea)

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, which 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. Manage weeds.

FRAC Group 4:

• mefenoxam (Ridomil Gold SL): 0.25 pt/A; PHI 21d, REI 48h. Do not apply to greenhouse or high tunnel crops . See label for application instructions and precautions.

FRAC Group 7:

• 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.

FRAC Group 11:

• azoxystrobin (Quadris F): 12.0 to 15.5 fl oz/A; PHI 0d, REI 4h. Rotate with a non-Group 11 fungicide. Phytotoxicity may occur. Proceed with caution when using tank mixes. See label for restrictions. Do not apply to greenhouse or high tunnel crops.
• 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. Do not apply to greenhouse or high tunnel crops. Do not make more than one application before alternating with a fungicide from a different resistance management group.
• 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.
• pyraclostrobin (Cabrio EG): 12.0 to 16.0 oz/A; PHI 0d, REI 12h. May cause leaf injury. Do not apply with anything other than water. Do not apply to greenhouse or high tunnel crops. See label for application restrictions. 

FRAC Group 21:

• cyazofamid (Ranman 400SC): 2.75 fl oz/A; PHI 0d, REI 12h. Do not plant other crops not registered for this product within 30 days of the last application. 

FRAC Group 27:

• cymoxanil (Curzate 60DF): 5.0 oz/A; PHI 1d, REI 12h. Use only in combination with a protectant fungicide. See label for crop rotation restrictions.
• 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.

FRAC Group 40:

• 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.
• mandipropamid (Revus): 5.5 to 8.0 fl oz/A; PHI 1d, REI 4h. Addition of adjuvant is recommended. 

FRAC Group 43:

• fluopicolide (Presidio 4SC): 3.0 to 4.0 fl oz/A; PHI 2d, REI 12h. 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.

FRAC Group 45:

• 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.

FRAC Group 49:

• oxathiapiprolin (Orondis Gold 200): 1.2 to 2.4 fl oz/A (foliar), 4.8 to 9.6 fl oz/A (soil application); PHI 0d, REI 4h. Apply at planting. Do not apply to greenhouse or high tunnel crops. 
• oxathiapiprolin plus mandipropamid (Orondis Ultra): 5.5 to 8.0 fl oz/A (foliar); PHI 1d, REI 4h, Groups 49 & 40. Apply with an adjuvant. Do not apply to greenhouse or high tunnel crops. See label for application restrictions.

FRAC Group BM02:

• Bacillus amyloliquefaciens strain D747 (Double Nickel LC^OG): 1.0 to 3.0 qt/A; PHI 0d, REI 4h. Suppression only. See label for other application methods and rates.

FRAC Group M01:

• copper hydroxide (Kocide 3000): 0.75 to 1.25 lb/A; PHI 0d, REI 48h. Flecking may occur.
• copper oxychloride plus copper hydroxide (Badge X2^OG): 0.75 to 1.25 lb/A; PHI 0d, REI 24h (greenhouse), 48h (field). Flecking may occur. See label for precautions.

FRAC Group P01:

• acibenzolar-S-methyl (Actigard 50WG): 0.5 to 0.75 oz/A; PHI 7d, REI 12h. 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.

FRAC Group P07:

• fosetyl aluminum (Aliette WDG): 2.0 to 5.0 lb/A; PHI 3d, REI 24h. 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.
• phosphorous acid (Fosphite): 1.0 to 3.0 qt/20 gal foliar; PHI 0d, REI 4h. Do not apply to plants that are heat- or moisture-stressed or recently treated with copper products.

Seed Decay

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

• azoxystrobin(Dynasty): 0.10 to 3.75 fl oz/100 lb seed; REI 14h, Group 11. 
• 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 fl oz/100 lb seed; REI 24h, Group M03.
• Streptomyces sp. strain K61 (MycoStop^OG): 0.04 to 4.0 oz/lb seed; REI 4h, Group BM02. See label for application methods. 

Stemphylium Leaf Spot (Stemphylium botryosum)

This relatively new disease of spinach was first detected in California in 2001 and has since become a problem in high tunnel production. 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. The pathogen is known to be seedborne. 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.

FRAC Group 7:

• fludioxonil plus pydiflumetofen (Miravis Prime): 9.2 to 13.4 fl oz/A; PHI 0d, REI 12h, Groups 12 & 7.

FRAC Group 12:

• fludioxonil plus pydiflumetofen (Miravis Prime): 9.2 to 13.4 fl oz/A; PHI 0d, REI 12h, Groups 12 & 7.

FRAC Group P06:

• Bacillus mycoides isolate J (LifeGard WG^OG): 1.0 to 4.5 oz/100 gal water/A; PHI 0d, REI 4h.

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. Symptoms begin as yellow spots on the upper leaf surface, while small, white pustules form on the undersides of leaves. The pathogen is not a true fungus but rather an Oomycete like the downy mildews. It produces oospores which can persist in soil and on contaminated seed for several years. Plant resistant cultivars and practice a 3-year crop rotation. Manage weeds. Apply preplant and foliar fungicides.

FRAC Group 4:

• mefenoxam (Ridomil Gold SL): 0.25 pt/A; PHI 21d, REI 48h.  Do not apply to greenhouse or high tunnel crops. Shank application 21 days after planting or after the first cutting for control of white rust. See label for application methods and precautions.

FRAC Group 11:

• azoxystrobin (Quadris F): 6.0 to 15.5 fl oz/A; PHI 0d, REI 4h. Quadris may be phytotoxic to spinach. See label for precautions. Do not apply to greenhouse or high tunnel crops.
• amoxadone 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. Do not apply to greenhouse or high tunnel crops.
• pyraclostrobin (Cabrio EG): 8.0 to 12.0 oz/A. PHI 0d, REI 12h. Do not apply to greenhouse or high tunnel crops. May cause crop injury under certain conditions. Do not apply as tank mix with anything other than water. See label for application restrictions. 

FRAC Group 21:

• cyazofamid (Ranman 400SC): 2.75 fl oz/A; PHI 0d, REI 12h.

FRAC Group 27:

• 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.

FRAC Group 43:

• fluopicolide (Presidio 4SC): 3.0 to 4.0 fl oz/A; PHI 2d, REI 12h. Must be used in a tank mix with a fungicide from a different FRAC Group. Do not apply to greenhouse or high tunnel crops.

FRAC Group M01:

• copper hydroxide (Kocide 3000): 0.75 to 1.25 lb/A; PHI 0d, REI 48h. 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. Flecking may occur. See label for precautions.

FRAC Group P01:

• acibenzolar-S-methyl (Actigard 50WG): 0.5 to 0.75 oz/A; PHI 7d, REI 12. 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.

FRAC Group P04:

• laminarin (Vacciplant): 14.0 to 22.0 fl oz/A; PHI 0d, REI 4h.

Cucumber Mosaic Virus (CMV)

CMV is found worldwide and infects over eight hundred crops 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. Grow resistant varieties such as Winter Bloomsdale and Renegade.