Disease Control

NOTE: For the disease control products listed below, one product trade name and formulation is 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 detail.

Bottom Rot (Rhizoctonia solani)

Rotate crops with non-hosts. Do not plant into fields having significant undecomposed crop residues. Plant in well-drained sites and avoid over-irrigation. Practice careful cultivar selection as more upright plants are less susceptible.

azoxystrobin (Quadris): 0.40 to 0.80  fl oz/1000 row feet; PHI 0d, REI 4h, Group 11. Apply in-furrow or as a banded application.

Bacillus amyloliquefaciens strain D747 (DoubleNickelOG): 0.12 to 1.0 lb/A as a soil drench; PHI 0d, REI 4 h, Group 44.

boscalid (Endura): 8.0 to 11.0 oz/A; PHI 14d, REI 12h, Group 7. Suppression only.

iprodione (Rovral 4 F): 1.5 to 2.0 pt/A; PHI 14d, REI 24h, Group 2. Lettuce only.  Direct application to soil and plant base.  Do not cultivate after application.

polyoxin D (OSO 5% SC): 3.75 to 13.0 fl oz/A; PHI 0d, REI 4h, Group 19.

Trichoderma asperellum, T. gamsii (Bio-tamOG): See label for in-furrow, drench, and broadcast rates; REI 1h, Group NC.

Gray Mold (Botrytis cinerea)

Avoid close planting and orient rows in the direction of prevailing winds. Do not plant in poorly drained areas. Plant on raised beds. Minimize damage to lettuce by cultural practices or other pathogens and pests. Avoid overhead irrigation. Do not plant where excessive plant residues are present. Transplanting mature plants results in more breakage. Direct seed Romaine lettuce as transplants are especially susceptible.

boscalid (Endura): 8.0 to 11.0 oz/A; PHI 14d, REI 12h, Group 7. Apply at seeding or transplant. A protective fungicide barrier is needed to maximize control.

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

penthiopyrad (Fontelis): 14.0 to 24.0 fl oz/A; PHI 3d, REI 12h, Group 7.

polyoxin D (OSO 5% SC): 3.75 to 13.0 fl oz/A; PHI 0d, REI 4h, Group 19.

Ulocladium oudemansii (BotryStopOG): 2-4 lbs/A; REI 4h, Group not applicable. Begin application when conditions are conducive to disease development.

Downy Mildew (Bremia lactucae)

Downy mildew is favored by cool, rainy weather. Night temperatures of 43°F to 50°F and day temperatures of 55°F to 70°F with 100% humidity are ideal for disease development. As temperatures increase, the disease disappears. Plant resistant cultivars. Use irrigation practices that reduce leaf wetness and humidity. Protect greenhouse grown transplants with fungicides so that the disease is not introduced into the field.

acibenzolar-S-methyl (Actigard 50 WG): 0.75 to 1.0 oz/A; PHI 7d, REI 12h, Group 21. Apply preventively on a 7-10 day schedule. See label for details.

ametoctradin & dimethomorph (Zampro): 14.0 fl oz/A; PHI 0d, REI 12h, Groups 45 & 40.

azoxystrobin (Quadris): 12.0 to 15.5 fl oz/A; PHI 0d, REI 4h, Group 11. Proceed with caution with regard to tank mixes and adjuvants. Do not rotate with other Group 11 fungicides.

copper compound (Badge X2OG): 1.75 to 3.5 lb/A; PHI 0d, REI 48h, Group M1. Rate and REI vary with product.

copper hydroxide (Kocide 3000): 0.75 to 1.5 lb/A; PHI 0d, REI 48h, Group M1. 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.

cyazofamid (Ranman): 2.75 fl oz/A; PHI 0d, REI 12h, Group 21.

cymoxanil (Curzate 60 DF): 3.2 to 5.0 oz/A; PHI 3d (head) and PHI 1d (leafy), REI 12h, Group 27. Must be applied as tank mix with a protectant fungicide.

dimethomorph (Forum):  6 fl oz/A; PHI 0d, REI 12h, Group 40. Must be applied as tank mix with another fungicide with a different mode of action.

famoxadone & cymoxanil (Tanos): 8 to 10 oz/A; PHI 1d, REI 12h, Groups 11 & 27. Tank mix with appropriate contact fungicide with a different mode of action. Do not make more than one application before alternating to a fungicide with a different mode of action.

fenamidone (Reason 500 SC): 5.5 to 8.2 fl oz/A; PHI 2d, REI 12h, Group 11. Do not make more than one application before alternating to a fungicide with a different mode of action. Do not alternate with Quadris.

fluopicolide (Presidio): 3.0 to 4.0 fl oz/A; PHI 2d, REI 12h, Group 43. Must be tank mixed with a fungicide with a different mode of action.

fluxapyroxad & pyraclostrobin (Merivon): 8.0 to 11.0 fl oz/A. PHI 21d, REI 12h, Groups 7 & 11.

fosetyl-Al (Aliette WDG): 2 to 5 lb/A; PHI 3d, REI 12h, Group 33. Do not tank mix with copper compounds or apply in a spray solution with a pH less than 6.0.

mancozeb (Dithane F45): 1.2 to 1.6 qt/A; PHI 10d (head) or PHI 14d (leaf), REI 24h, Group M3.

mancozeb plus copper hydroxide (ManKocide): 1.0 to 2.0 lb/A; PHI 10d, REI 48 h, Groups M3 & M1. 

mandipropamid (Revus): 8 fl oz/A; PHI 1d, REI 4h, Group 40. Addition of a spreading/penetrating adjuvant is recommended.

oxathiapiprolin (Orondis Ultra A): 2.0-4.8 fl.oz/A; PHI 0d, REI 4h, Group 49. Begin foliar application prior to disease development.

propamocarb HCl (Previcur Flex): 2 pt/A; PHI 2d, REI 12h, Group 28.

pyraclostrobin (Cabrio EG): 16.0 oz/A; PHI 0d, REI 12h, Group 11.

Drop, White Mold (Sclerotinia minor)

Do not plant seed contaminated with sclerotia (small black hardened fungal survival structures). Avoid planting into severely infested fields. Rotate with non-host crops like grasses. 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. Incorporation of crop residues from brassica crops may provide a suppressive effect.

boscalid (Endura): 8.0 to 11.0 oz/A; PHI 14d, REI 12h, Group 7. Apply at seeding or transplant. A protective fungicide barrier is needed to maximize control.

Coniothyrium minitans (Contans WGOG): Apply 1 to 4 lb/A in 20 to 50 gal water; REI 4h, Group NC. Spray on the soil surface and incorporate into the top 2" of soil. Fall application is best or 3 to 4 months before planting to allow for the biocontrol agent to infect the sclerotia of Sclerotinia.

cyprodinil plus fludioxonil (Switch 62.5 WG): 11.0 to 14.0 oz/A; PHI 0d, REI 12h, Groups 9 & 1.

fludioxonil (Cannonball WG): 7.0 oz/A; PHI 0d, REI 12h, Group 12.

fluxapyroxad & pyraclostrobin (Merivon): 8.0 to 11.0 fl oz/A. PHI 21d, REI 12h, Groups 7 & 11.  

iprodione (Rovral 4F): 1.5 to 2 pt/A; PHI 14d, REI 24h, Group 2. Lettuce only. Direct application to lower stems and branches and adjacent soil surface.  Do not cultivate after application.

penthiopyrad (Fontelis): 16.0 to 24.0 fl oz/A; PHI 3d, REI 12h, Group 7.

polyoxin D (OSO 5% SC): 3.75 to 13.0 fl oz/A; PHI 0d, REI 4h, Group 19.

Trichoderma asperellum, T. gamsii (Bio-tamOG): See label for in-furrow, drench, and broadcast rates; REI 4h, Group NC.

Ulocladium oudemansii (BotryStopOG): 2-4 lbs/A; REI 4h, Group not applicable. Begin application when conditions are conducive to disease development.

Seed Decay

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

mefenoxam (Apron XL): 0.085 to 0.64 fl oz/100 lb seed; REI 48h, Group 4. For Pythium damping-off protection.

fludioxonil (Maxim 4FS): 0.08 to 0.16 oz/100 lb seed; REI 12h, Group 12. For protection against seed-borne and soil-borne fungi. Does not control Pythium or Phytophthora.

thiram (Thiram SC): 8.0 fl oz/100 lb seed; REI 24h, Group M3.

Mosaic (Lettuce and Cucumber Mosaic Viruses)

Plant mosaic-indexed seed away from old lettuce fields.

Yellows

Do not plant lettuce or other sensitive crops in fields or areas having a history of this disease. Control alternate weed hosts. Control leafhoppers, which carry the disease-causing organism (phytoplasma).