Disease Control

Aster Yellows (Candidatus Phytoplasma asteris)

Aster yellows affect a wide range of crops, ornamentals, and weeds. The disease is caused by phytoplasma, a wall-less bacterium that is incapable of living outside of its host plant or its vector, the aster leaf hopper. Symptoms of aster yellows in lettuce and related crops include stunting, yellowing, and twisted or deformed leaves. Do not plant lettuce or other sensitive crops in fields  with a history of this disease. Remove infected plants and destroy crop residues immediately after harvest. Manage weeds, especially those in the Asteraceae family, and control leafhoppers (see the Insect Control section https://nevegetable.org/crops/lettuce-endive-and-escarole/insect-control)

Bottom Rot (Rhizoctonia solani)

Bottom rot begins as brown spots on the outer leaves where they are in contact with the soil. As the disease progresses, entire leaves may turn brown and slimy. Web-like mycelium and brown sclerotia may be observed. Disease development is favored by moist soil and temperatures 75-81°F. The pathogen survives as mycelium and sclerotia in the soil. Rotate crops with unrelated non-host plants. .  Remove infected plant material or plow deeply after harvest to hasten decomposition of crop residues. Plant in well-drained sites and avoid overhead irrigation. Manage weeds. Cultivars with upright growth habits are less susceptible.

FRAC Group 2:

• iprodione (Rovral 4 F): 1.5 to 2.0 pt/A; PHI 14d, REI 24h. Lettuce only. Direct application to soil and plant base. See label for restrictions. Do not cultivate after application.

FRAC Group 7: 

• boscalid (Endura): 8.0 to 11.0 oz/A; PHI 14d, REI 12h. For disease suppression. Lettuce only.

FRAC Group 11:

• azoxystrobin (Abound F, Quadris F): 0.40 to 0.80 fl oz/1000 row feet; PHI 0d, REI 4h. See label for tank mixing restrictions.

FRAC Group 19:

• polyoxin D zinc salt (OSO 5% SC^OG): 6.5 to 13.0 fl oz/A; PHI 0d, REI 4h.

FRAC Group BM02:

• Bacillus amyloliquefaciens strain D747 (Double Nickel 55^OG): 0.125 to 1.0 lb/A as a soil drench; PHI 0d, REI 4h..

Downy Mildew (Bremia lactucae)

Downy mildew causes angular yellow spots on the upper surfaces of leaves. These spots eventually turn brown. Under humid conditions, white sporulation may be visible on the undersides of leaves. Older leaves are often the first to show symptoms. Lettuce downy mildew is favored by cool, rainy weather. Night temperatures of 43°F to 50°F and day temperatures of 55-70°F with 100% humidity are ideal for disease development. As temperatures increase, the disease disappears. 

Plant resistant cultivars. Ventilate greenhouses and use irrigation practices that reduce leaf wetness and humidity. Protect greenhouse grown transplants with fungicides to prevent the disease from being introduced to the field.

FRAC Group 7:

• fluxapyroxad plus pyraclostrobin (Merivon Xemium): 8.0 to 11.0 fl oz/A. PHI 1d, REI 12h, Groups 7 & 11.

FRAC Group 11:

• azoxystrobin (Quadris F): 12.0 to 15.5 fl oz/A; PHI 0d, REI 4h. Proceed with caution with regard to tank mixes and adjuvants. Do not rotate with other Group 11 fungicides.
• famoxadone plus cymoxanil (Tanos): 8.0 to 10.0 oz/A; PHI 1d, REI 12h, Groups 11 & 27. Tank mix with appropriate contact fungicide from a different FRAC Group. Do not make more than 1 application before alternating to a fungicide from a different FRAC Group.
• fenamidone (Reason 500 SC): 5.5 to 8.2 fl oz/A; PHI 2d, REI 12h. Do not make more than one application before alternating to a fungicide from a different FRAC Group. Do not alternate with Quadris.
• fluxapyroxad plus pyraclostrobin (Merivon Xemium): 8.0 to 11.0 fl oz/A. PHI 1d, REI 12h, Groups 7 & 11.
• pyraclostrobin (Cabrio EG): 16.0 oz/A; PHI 0d, REI 12h. See label for crop sensitivity warnings.

FRAC Group 21:

• cyazofamid (Ranman 400SC): 2.75 fl oz/A; PHI 0d, REI 12h. Should be tank mixed with a surfactant. See label for restrictions.

FRAC Group 27: 

• cymoxanil (Curzate 60 DF): 3.2 to 5.0 oz/A; PHI 3d (head), 1d (leafy), REI 12h. Lettuce only. Must be applied as tank-mix with a protectant fungicide.
• famoxadone plus cymoxanil (Tanos): 8.0 to 10.0 oz/A; PHI 1d, REI 12h, Groups 11 & 27. Tank mix with appropriate contact fungicide from a different FRAC Group. Do not make more than 1 application before alternating to a fungicide from a different FRAC Group.

FRAC Group 28:

• propamocarb hydrochloride (Previcur Flex): 1.33 to 2.0 pt/A; PHI 2d, REI 12h. See label for tank mix restrictions.

FRAC Group 40:

• ametoctradin plus dimethomorph (Zampro): 14.0 fl oz/A; PHI 0d, REI 12h, Groups 45 & 40. Do not make more than 3 applications per year. 
• dimethomorph (Forum): 6.0 fl oz/A; PHI 0d, REI 12h. Must be applied as tank mix with another fungicide from a different FRAC Group.
• mandipropamid (Revus): 5.5 to 8.0 fl oz/A; PHI 1d, REI 4h. Addition of a spreading/penetrating adjuvant is recommended.

FRAC Group 43:

• fluopicolide (Presidio 4SC): 3.0 to 4.0 fl oz/A; PHI 2d, REI 12h. Must be tank mixed with a fungicide from a different FRAC Group.

FRAC Group 45:

• ametoctradin plus dimethomorph (Zampro): 14.0 fl oz/A; PHI 0d, REI 12h, Groups 45 & 40. Do not make more than 3 applications per year. 

FRAC Group 49: 

• oxathiapiprolin (Orondis): 1.0 to 19.2 fl oz/A (see label); PHI 0d, REI 4h. See label for application methods and restrictions. 

FRAC Group BM02:

• Streptomyces lydicus strain WYEC 108 (Actinovate AG^OG): 3.0 to 12.0 oz/A (foliar); PHI 0d, REI 4h. See label for application restrictions. 

FRAC Group M01: 

• copper oxychloride plus copper hydroxide (Badge X2^OG): 0.75 to 1.5 lb/A; PHI 0d, REI 48h field, 24h greenhouse. May cause slight crop injury. See label for application restrictions.
• copper hydroxide (Kocide 3000): 0.75 to 1.5 lb/A; PHI 0d, REI 48h. Do not apply in a spray solution having a pH less than 6.5 or tank mix with Aliette. Injury may occur to sensitive lettuce cultivars.
• mancozeb plus copper hydroxide (ManKocide): 1.0 to 2.0 lb/A; PHI 10d, REI 48h and 24h (greenhouse), Groups M03 & M01. May cause injury to some varieties of lettuce. See label for restrictions.

FRAC Group M03: 

• mancozeb (Dithane F45): 1.2 to 1.6 qt/A; PHI 10d (head), 14d (leaf), REI 24h. Lettuce only. See label for application restrictions. 
• mancozeb plus copper hydroxide (ManKocide): 1.0 to 2.0 lb/A; PHI 10d, REI 48h/24h (field and greenhouse), Groups M03 & M01. May cause injury to some varieties of lettuce. See label for restrictions.

FRAC Group P01:

• acibenzolar-S-methyl (Actigard 50 WG): 0.75 to 1.0 oz/A; PHI 7d, REI 12h. See label for crop injury warning and application restrictions.

Gray Mold (Botrytis cinerea)

Botrytis causes crown and leaf rot of lettuce under cool, humid conditions. Fuzzy, gray sporulation is typically visible. Black sclerotia may be observed.

Avoid close planting and orient rows in the direction of prevailing winds. Plant in well-drained soil. Utilize raised beds when available. Minimize damage to lettuce incurred through cultural practices (e.g., scouting, weeding, etc.) or by other pathogens and pests. Avoid overhead irrigation. Do not plant where excessive plant residues are present. Romaine lettuce types are especially susceptible.

FRAC Group 7: 

• boscalid (Endura): 8.0 to 11.0 oz/A; PHI 14d, REI 12h. Apply at seeding or transplant. A protective fungicide barrier is needed to maximize control.
• penthiopyrad (Fontelis): 14.0 to 24.0 fl oz/A; PHI 3d, REI 12h.

FRAC Group 9: 

• cyprodinil plus fludioxonil (Switch 62.5 WG): 11.0 to 14.0 oz/A; PHI 0d, REI 12h, Groups 9 & 12. 

FRAC Group 12: 

• cyprodinil plus fludioxonil (Switch 62.5 WG): 11.0 to 14.0 oz/A; PHI 0d, REI 12h, Groups 9 & 12. 

FRAC Group 19:

• polyoxin D zinc salt (OSO 5% SC^OG): 6.5 to 13.0 fl oz/A; PHI 0d, REI 4h. See label for restrictions. 

FRAC Group BM02:

• Ulocladium oudemansii U3 strain (BotryStop WP^OG): 2.0 to 4.0 lb/A; REI 4h. Use preventively. 

FRAC Group P04:

• laminarin (Vacciplant): 14.0 to 22.0 fl oz/A; PHI 0d, REI 4h. For preventive use. Not labeled for escarole. 

Lettuce Drop, White Mold (Sclerotinia minor and S. sclerotiorum)

The disease begins with wilting and rotting outer leaves. Heads may eventually collapse. Under humid conditions, white mycelium and black sclerotia are observed in infected tissues. 

Do not plant seed contaminated with sclerotia (small black hardened fungal survival structures). Avoid planting into severely infested fields. Rotate with non-host crops  such as corn or small grains. Avoid excessive nitrogen fertilization and irrigate in the morning or with sub-surface drip irrigation to provide dry soil. Deep plow after harvest to bury sclerotia. Soil sterilization with chemicals, steam, or heat (solarization) treatments can significantly reduce inoculum levels. Biofumigation with a brassica crop may provide a suppressive effect.

FRAC Group 2:

• iprodione (Rovral 4F): 1.5 to 2 pts/A; PHI 14d, REI 24h. Lettuce only. Direct application to lower stems and branches and adjacent soil surface. See label for restrictions; do not cultivate after application.

FRAC Group 7: 

• boscalid (Endura): 8.0 to 11.0 oz/A; PHI 14d, REI 12h. Apply at seeding or transplant. A protective fungicide barrier is needed to maximize control.
• fluxapyroxad plus pyraclostrobin (Merivon Xemium): 8.0 to 11.0 fl oz/A. PHI 1d, REI 12h, Groups 7 & 11.
• penthiopyrad (Fontelis): 16.0 to 24.0 fl oz/A; PHI 3d, REI 12h.

FRAC Group 9: 

• cyprodinil plus fludioxonil (Switch 62.5 WG): 11.0 to 14.0 oz/A; PHI 0d, REI 12h, Groups 9 & 12. Apply once at thinning and again 2 weeks later.

FRAC Group 11:

• fluxapyroxad plus pyraclostrobin (Merivon Xemium): 8.0 to 11.0 fl oz/A. PHI 1d, REI 12h, Groups 7 & 11.

FRAC Group 12: 

• fludioxonil (Cannonball WG): 5.5 to 7.0 oz/A; PHI 0d, REI 12h. See label application restrictions. 

FRAC Group 19: 

• polyoxin D zinc salt (OSO 5% SC^OG): 6.5 to 13.0 fl oz/A; PHI 0d, REI 4h. See label for application instructions.

FRAC Group BM02:

• Bacillus subtilis strain QST 713 (Minuet^OG): 12.0 to 24.0 oz/A; PHI 0d, REI 4h. 
• Coniothyrium minitans strain CON/M/91-08 (LALStop Contans^OG WG, Contans^OG WG): 1.0 to 4.0 lb/A; PHI 0d, REI 4h, Group BM02. Spray on the soil surface and incorporate into the top 2" of soil. Fall application is best 3-4 months before planting to allow for the biocontrol agent to infect the sclerotia of Sclerotinia. See label for application restrictions.
• Streptomyces lydicus strain WYEC 108 (Actinovate AG^OG): 3.0 to 12.0 oz/A (soil); PHI 0d, REI 4h. See label for application instructions. 
• Ulocladium oudemansii U3 strain (BotryStop WP^OG): 2.0 to 4.0 lb/A; REI 4h. Begin application when conditions are conducive to disease development.

Lettuce Mosaic Virus and Cucumber Mosaic Virus

LMV and CMV cause mottled and/or misshapen leaves. Brown lesions may also be seen. Both viruses are transmitted by aphids in a non-persistent manner. Use certified LMV- and CMV-free seed. Do not plant certified disease-free seed  in old lettuce fields. Manage weeds.

Powdery Mildew (Golovinomyces (Erysiphe) cichoracearum)

Lettuce powdery mildew is favored by warm weather and dry to mildly humid conditions. Unlike many other pathogens, growth of powdery mildew is inhibited by water on leaf surfaces. The fungus presents as powdery white growth on both upper and lower surfaces of leaves. Older leaves are affected first. Affected leaves eventually turn yellow  and die. Plants affected before maturity are often not marketable. Plant resistant varieties when available. Manage weeds, especially those in the Asteraceae. Rotate among fungicide groups to minimize risk of resistance. 

FRAC Group 3: 

• azoxystrobin plus flutriafol (TopGuard EQ): 6.0 to 8.0 oz/A; PHI 7d, REI 12h, Groups 3 & 11. See label for tank mixing restrictions and phytotoxicity warnings. Not for greenhouse use.
• flutriafol (Rhyme): 5.0 to 7.0 fl oz/A; PHI 7d, REI 12h. Apply as preventatively. Not for greenhouse use.
• myclobutanil (Rally 40WSP): 5.0 oz/A; PHI 3d, REI 24h. Lettuce only.
• triflumizole (Procure 480 SC): 6.0 to 8.0 fl oz/A; PHI 0d, REI 12h. Do not make more than 2 applications per crop year. Not labeled for use in Maine.

FRAC Group 7: 

• fluopyram (Velum Prime): 6.84 fl oz/A; PHI 0d (field) 3d (greenhouse), REI 12h. For suppression only. Do not make more than 2 sequential applications before rotating to different FRAC Group.
• fluxapyroxad plus pyraclostrobin (Merivon Xemium): 4.0 to 11.0 fl oz/A; PHI 1d, REI 12h, Groups 7 & 11. Make no more than 2 sequential applications before alternating with fungicides from a different FRAC Group. Not for greenhouse use.
• penthiopyrad (Fontelis): 14.0 to 24.0 fl oz/A; PHI 3d, REI 12h.
•  pydiflumetofen plus fludioxonil (Miravis Prime): 6.8 to 13.4 fl oz/A, PHI 0d, REI 12h, Groups 12 & 7. Begin application preventively. 

FRAC Group 9: 

• cyprodinil plus fludioxonil (Switch 62.5 WG): 11.0 to 14.0 oz/A; PHI 0d, REI 12h, Groups 9 & 12. For suppression only. 

FRAC Group 11:

• azoxystrobin (Quadris F): 12.0 to 15.5 fl oz/A; PHI 0d, REI 4h. Not labeled for escarole. See label for tank mix precautions. Do not use for transplant production in greenhouse.
• azoxystrobin plus flutriafol (TopGuard EQ): 6.0 to 8.0 oz/A; PHI 7d, REI 12h, Groups 3 & 11. See label for tank mixing restrictions and phytotoxicity warnings. Not for greenhouse use.
• fluxapyroxad plus pyraclostrobin (Merivon Xemium): 4.0 to 11.0 fl oz/A; PHI 1d, REI 12h, Groups 7 & 11. Make no more than 2 sequential applications before alternating with fungicides from a different FRAC Group. Not for greenhouse use.
• pyraclostrobin (Cabrio EG): 12.0 to 16.0 oz/A; PHI 0d, REI 12h. Do not rotate with other Group 11 fungicides. See label for crop injury warnings. Not for greenhouse use.

FRAC Group 12: 

• cyprodinil plus fludioxonil (Switch 62.5 WG): 11.0 to 14.0 oz/A; PHI 0d, REI 12h, Groups 9 & 12. For suppression only. 
• pydiflumetofen plus fludioxonil (Miravis Prime): 6.8 to 13.4 fl oz/A, PHI 0d, REI 12h, Groups 12 & 7. Begin application preventively. 

FRAC Group 13:

• quinoxyfen (Quintec): 4.0 to 6.0 fl oz/A; PHI 1d, REI 12h. Lettuce only. See label for application precautions. Not for greenhouse use.

FRAC Group 19:

• polyoxin D zinc salt (OSO 5%SC^OG): 6.5 to 13.0 fl oz/A; PHI 0d, REI 4h. Apply as foliar spray in sufficient water to achieve thorough coverage. See label for restrictions.

FRAC Group P06:

• Bacillus mycoides Isolate J (LifeGard WG^OG): 4.5 oz/100 gal/A; PHI 0d, REI 4h. See label for additional volumes and rates.

FRAC Group BM01:

• Swinglea glutinosa extract (EcoSwing^OG): 1.5 to 2.0 pts/A; PHI 0d, REI 4h. See label for application restrictions. Lettuce only. 

FRAC Group BM02:

• Bacillus subtilis strain QST 713 (Serenade ASO^OG): 2.0 to 4.0 qt/A; PHI 0d, REI 4h. See label for precautions.
• Pseudomonas chlororaphis strain AFS009 (Howler EVO^OG): 2.5 to 7.5 lb/A; PHI 0d, REI 4h. See label for application method and directions.
• Streptomyces lydicus strain WYEC 108 (Actinovate AG^OG): 3.0 to 12.0 oz/A; PHI 0d, REI 4h. Apply to foliage with spreader-sticker for best results.

FRAC Group M01:

• copper oxychloride plus copper hydroxide (Badge X2^OG): 0.75 to 1.5 lb/A; PHI 0d, REI 48h field, 24h greenhouse. May cause slight crop injury. See label for application restrictions.

FRAC Group M02: 

• sulfur (Microthiol Disperss^OG): 4.0 to 10.0 lb/A; PHI 0d, REI 24h. Thorough coverage is required. Start with lowest rate for greenhouse crops to avoid plant injury. See label for applications restrictions.

FRAC Group NC:

• hydrogen peroxide plus peroxyacetic acid (ZeroTol 2.0^OG): See label for application rates; PHI 0d, REI 1h. Use as a preventive or curative. See label for application instructions and specific dilution rates.
• paraffinic oil (JMS Stylet-Oil): 3.0 to 6.0 qt/100 gal water; PHI 0d, REI 4h. Lettuce only. Spray for thorough coverage of upper leaf surface. An organic formulation is available. Not labeled for use in New Hampshire.
• potassium bicarbonate (MilStop SP^OG): 1.25 to 5.0 lb/100 gal water/A; PHI 0d, REI 1h. Thorough crop coverage is required. May be used in greenhouses. See label for application restrictions.
• potassium salts of fatty acids (M-Pede^OG): See label for application rates; PHI 0d, REI 12h. See label for precautions and application methods. 

FRAC Group P05: 

• Reynoutria sachalinensis extract (Regalia^OG): 0.5 to 1.0 qt/A; PHI 0d, REI 4h. Ensure thorough coverage. See label for specific rates and application restrictions.

Seed Decay

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

FRAC Group 4: 

• mefenoxam (Apron XL): 0.085 to 0.64 fl oz/100 lb seed; REI 48h. For Pythium damping-off protection. Not labeled for use in Maine.

FRAC Group 12: 

• fludioxonil (Maxim 4FS): 0.08 to 0.16 oz/100 lb seed; REI 12h. For protection against seedborne and soilborne fungi. Does not control Pythium or Phytophthora.

FRAC Group M03: 

• thiram (Thiram SC): 8.0 fl oz/100 lb seed; REI 24h. See label for seed treatment instructions.