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 say 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.

Management practices that will reduce disease in greenhouses and high tunnels are the use of resistant varieties, sanitation, fungicides and cultural practices that keep the humidity below 90%.

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

Anthracnose (Colletotrichum gloeosporioides and C. scovillei)

Anthracnose caused by Colletotrichum gloeosporioides occurs primarily on ripe fruit . Latent infections can occur on immature fruit, but symptoms do not appear until ripening. Fruit develop sunken circular lesions that produce salmon-pink spores. Anthracnose caused by Colletotrichum scovillei (formerly C. acutatum) is relatively new to the pepper industry in the U.S. It is fairly widespread in the southern U.S. and has occurred for consecutive years in several New England states. The symptoms are similar to those caused by C. gloeosporioides, but C. scovillei attacks fruit of all ages and is very aggressive. 

During warm and wet weather conditions, significant losses can occur. Do not plant peppers in the same area following disease for at least 2 years. Remove all diseased plant material from the field. Colletotrichum species can be seedborne and survive in the soil through the production of sclerotia. Plant in well-drained fields. Control solanaceous weeds. Studies indicate that some hot peppers varieties such as ‘Roulette,’ ‘Tabasco,’ and ‘Carolina Reaper’ are resistant; however, resistance has yet to be found in bell peppers. ‘North Star’ and ‘Paladin’ were the least susceptible in one report. Apply fungicides preventively where anthracnose has been a problem.

FRAC Group 3: 

• azoxystrobin plus difenoconazole (Quadris Top): 8.0 to 14.0 fl oz/A; PHI 0d, REI 12h, Groups 11 & 3.
• difenoconazole plus benzovindiflupyr (Aprovia Top): 8.5 to 13.5 fl oz/A; PHI 0d, REI 12h, Groups 3 & 7.
• tetraconazole (Mettle 125ME): 6.0 to 8.0 fl oz/A; PHI 0d, REI 12h. Rotate to a non-Group 3 fungicide after 2 applications.

FRAC Group 7: 

• difenoconazole plus benzovindiflupyr (Aprovia Top): 8.5 to 13.5 fl oz/A; PHI 0d, REI 12h, Groups 3 & 7.
• fluxapyroxad plus pyraclostrobin (Priaxor Xemium): 4.0 to 8.0 fl oz/A; PHI 0d, REI 12, Groups 7 & 11.

FRAC Group 11:

• azoxystrobin (Quadris F): 6.0 to 15.5 fl oz/A; PHI 0d, REI 4h. Do not rotate with other Group 11 fungicides.
• azoxystrobin plus difenoconazole (Quadris Top): 8.0 to 14.0 fl oz/A; PHI 0d, REI 12h, Groups 11 & 3.
• famoxadone plus cymoxanil (Tanos): 8.0 to 10.0 oz/A; PHI 3d, REI 12h, Group 11 & 27. Tank mix with an appropriate contact fungicide.
• fluxapyroxad plus pyraclostrobin (Priaxor Xemium): 4.0 to 8.0 fl oz/A; PHI 0d, REI 12, Groups 7 & 11.
• pyraclostrobin (Cabrio EG): 8.0 to 12.0 oz/A; PHI 0d, REI 12h. Rotate to a non-Group 11 fungicide after 1 application.
• trifloxystrobin (Flint): 3.0 to 4.0 fl oz/A; PHI 3d, REI 12h.

FRAC Group 19:

• polyoxin D zinc salt (OSO 5%SC^OG): 6.5 to 13.0 fl oz/A; PHI 0d, REI 4h, Group 19.

FRAC Group 27: 

• famoxadone plus cymoxanil (Tanos): 8.0 to 10.0 oz/A; PHI 3d, REI 12h, Group 11 & 27. Tank mix with an appropriate contact fungicide.

FRAC Group M01: 

• copper hydroxide (Kocide 3000): 0.75 to 1.25 lb/A; PHI 0d, REI 48h, Group M01. See label for restrictions. 

FRAC Group M03: 

• flutriafol (Rhyme): 7.0 fl oz/A; PHI 0d, REI 12h.
• mancozeb (Dithane F45): 1.2 to 2.4 lb/A; PHI 7d, REI 24h.

FRAC Group M05: 

• chlorothalonil (Bravo Weather Stik): 1.5 pt/A; PHI 3d, REI 12h.

Damping-Off and Seed Decay

Do not allow transplant growing medium to remain wet. Maintain ventilation. Do not use unpasteurized growing media. Keep tools and hose nozzles clean and off of the greenhouse floor. 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. Do not make a preplant or at-plant application of products containing mefenoxam.

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 and Phytophthora.

FRAC Group 28:

• propamocarb HCl (Previcur Flex): 1.2 pt/A; PHI 5d, REI 12h. Pythium and Phytophthora damping-off. For greenhouse or high tunnel use, see label: apply in evening to avoid intense sunlight after application. Phytotoxicity may occur if applied directly to dry growing media, especially in intense sunlight.

Phytophthora Crown Rot and Blight (Phytophthora capsici)

Symptoms include total collapse of plants and water-soaked lesions on fruit which produce a white yeasty growth under moist conditions. Avoid planting into soils that are known to be contaminated with Phytophthora capsici. P. capsici can survive in the soil for many years; a 3-year or longer rotation with plants other than pepper, tomato, eggplant, cucurbits, or legumes may help reduce losses. If planting into infested soils, subsoil to improve drainage, use resistant varieties, and plant on dome-shaped raised beds that will shed water. Break beds to allow water to leave field through lowest paths; do not let water pool or stand around plants. Avoid bringing Phytophthora-contaminated soil into clean or fumigated fields on farm equipment by working in clean fields first and cleaning equipment after working in contaminated fields. Avoid planting low, wet areas with susceptible crops. Do not throw rotting host crops purchased off-farm on fields or into compost piles for use on fields. Alternating between two or more soil-applied fungicides, beginning at planting, and continuing throughout the season, has been shown to be more effective than foliar applications. Several products are labeled for drench or trickle applications.

For crown and stem rot:

FRAC Group 4:

• mefenoxam (Ridomil Gold SL): 1.0 pt/A; PHI 7d, REI 48h. Apply as banded spray after transplant. May cause yellowing of pepper leaves, especially if soil applications are made when the soil is dry. See label for plant back restrictions and precautions. Does not control foliar/fruit phase. Resistance is a frequent problem.

FRAC Group 21:

• cyazofamid (Ranman): 2.75 oz/A; PHI 0d, REI 12h. Labeled for foliar, soil drench or overhead irrigation application.

FRAC Group 22:

• ethaboxam (Elumin): 8.0 fl oz/A; PHI 2d, REI 12h. For best results, begin applications at planting/transplanting. Do not make more than 2 applications per year.

FRAC Group 40:

• ametoctradin plus dimethomorph (Zampro): 14.0 fl oz/A; PHI 4d, REI 12h, Groups 45 & 40. Labeled for foliar, soil, and drip applications. Do not use in greenhouse or high tunnel crops.
• dimethomorph (Forum): 6.0 oz/A; PHI 0d, REI 12h. Suppression only. Must be applied as a tank mix with another fungicide from a different FRAC Group. Do not make more than 2 consecutive applications before alternating to a non-Group 40 fungicide. Do not use in greenhouse or high tunnel crops.

FRAC Group 43:

• fluopicolide (Presidio 4SC): 3.0 to 4.0 fl oz/A; PHI 2d, REI 12h. Must be applied in a tank mix with another fungicide from a different FRAC Group. Labeled for foliar, soil, and drip applications. Do not use in greenhouse or high tunnel crops.

FRAC Group 45:

• ametoctradin plus dimethomorph (Zampro): 14.0 fl oz/A; PHI 4d, REI 12h, Groups 45 & 40. Labeled for foliar, soil, and drip applications. Do not use in greenhouse or high tunnel crops.

FRAC Group 49:

• oxathiapiprolin (Orondis Gold 200): 2.4 to 19.2 fl oz/A; PHI 0d, REI 4h. Apply at planting in furrow, in transplant water, or by drip irrigation.

FRAC Group BM02:

• Bacillus subtilis strain QST 713 (Serenade Soil ^OG): 2.0 to 4.0 qt/A; PHI 0d, REI 4h. Apply as an in-furrow spray in 5-15 gallons of water at planting.
• Streptomyces lydicus strain WYEC 108 (Actinovate AG^OG): 3.0 to 12.0 oz/A (soil applied); PHI 0d, REI 3h. See label for application restrictions.

FRAC Group P07:

• potassium phosphite (ProPhyt): 4.0 pt/100 gal to transplants prior to transplanting, or 5 fl oz/1000 row ft as in-furrow drench at planting; PHI 0d, REI 4h. 

For foliar and fruit rot:

FRAC Group 4:

• mefenoxam plus copper hydroxide (Ridomil Gold/Copper): 1.0 pt/A; PHI 7d, REI 48h, Groups 4 & M01. Recommended to be used in conjunction with Ridomil Gold SL. See label for rates and restrictions. Do not use in greenhouse or high tunnel crops.

FRAC Group 11:

• famoxadone plus cymoxanil (Tanos): 8.0 to 10.0 oz/A; PHI 3d, REI 12h, Groups 11 & 27. Disease suppression of foliar and fruit phase only. Rotate with an appropriate fungicide from a different FRAC Group. Must be tank-mixed with a contact fungicide.

FRAC Group 27: 

• famoxadone plus cymoxanil (Tanos): 8.0 to 10.0 oz/A; PHI 3d, REI 12h, Groups 11 & 27. Disease suppression of foliar and fruit phase only. Rotate with an appropriate fungicide from a different FRAC Group. Must be tank-mixed with a contact fungicide.

FRAC Group 40: 

• oxathiapiprolin plus mandipropamid (Orondis Ultra): 5.5 to 8.0 fl oz/A; PHI 1d, REI 4h, Groups 49 & 40. Begin prior to disease development.

FRAC Group 49:

• oxathiapiprolin plus mandipropamid (Orondis Ultra): 5.5 to 8.0 fl oz/A; PHI 1d, REI 4h, Groups 49 & 40. Begin prior to disease development.

FRAC Group M01: 

• mefenoxam plus copper hydroxide (Ridomil Gold/Copper): 1.0 pt/A; PHI 7d, REI 48h, Groups 4 & M01. Recommended to be used in conjunction with Ridomil Gold SL. See label for rates and restrictions. Do not use in greenhouse or high tunnel crops.

FRAC Group BM02: 

• Gliocladium virens strain GL-21 (SoilGard^OG):0.5 to 2.0 lb/100 gal; 2.0 to 10 lb/A; PHI 0d, REI 4h. See label for specific rates (before, at, and after transplanting).

FRAC Group P07:

• potassium phosphite (ProPhyt): 6.0 pt/A; PHI 0d, REI 4.

Bacterial Canker (Clavibacter michiganensis pv. michiganensis)

Bacterial canker (Cmm) is primarily a disease of tomatoes but can also infect pepper. This disease is seedborne. Damage appears as irregular-shaped brown leaf spots, black cankers, wilting, defoliation, and occasionally as tiny, round, brown fruit spots with a white center. Management is similar to methods listed below for bacterial spot.

Bacterial Leaf Spot (Xanthomonas spp.)

Bacterial leaf spot is one of the most destructive diseases of peppers in New England. There are several identified races. Symptoms include brown leaf lesions which often have yellow haloes. Severe infection may lead to defoliation. Small round spots may be seen on fruit. The disease is most active in wet conditions and temperatures of 75-86°F. The pathogen can be seed-borne.  Chemical controls are often ineffective. Effective management requires rotating to fields where solanaceous crops and weeds have not existed for at least 2 years and growing resistant varieties. Success using resistant varieties requires growing a variety with resistance to the race(s) present in your crop. X10R™ varieties provide intermediate resistance to all strains. Maintain proper nutrient levels and avoid using dolomitic (high magnesium) lime before planting peppers. Hot water treat pepper seeds at 122°F for 25 minutes to eliminate seedborne inoculum. Grow your own transplants or contract to have them grown locally. Disinfect used flats, cell-packs, bench tops, machinery, etc. with a 1:9 mix of bleach and water; rinse well with fresh water. Use proper spacing to facilitate rapid drying of foliage after irrigation or rain. Scout fields weekly for plants with small brown leaf spots. Work infected fields last. Do not use high pressure, air-blast sprayers, which cause increased leaf infection in rows adjacent to spray alleys and spread bacterial diseases across rows. Destroy crop residue after harvest to encourage rapid decomposition.

FRAC Group 25:

• streptomycin sulfate (Agri-Mycin 17): 200 ppm (1 lb/100 gal); REI 12h. Only for greenhouse use on transplants; do not use in the field grown crops. Apply when the first true leaves appear and continue every 4-5 days until field transplanting.

FRAC Group BM02:

• Bacillus amyloliquefaciens strain D747 (Double Nickel LC^OG ): 1.0 to 3.0 qt/A; PHI 0d, REI 4 h. Suppression only. For improved control, mix or rotate with a chemical fungicide.

FRAC Group M01: 

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

FRAC Group P01:

• acibenzolar-S-methyl (Actigard 50 WG): 0.33 to 0.75 oz/A; PHI 14d, REI 12h.  Actigard is a plant activator and should be applied preventatively before disease symptoms are observed.

FRAC Group P04:

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

FRAC Group P06:

• Bacillus mycoides Isolate J (LifeGard LC^OG ): 1 gal/100 gal water; PHI 0d, REI 4.

FRAC Group NC:

• Bacillus thurigiensis subsp. kurstaki strain ABTS-351 plus methyl salicylate (Leap ES): 0.5 to 2.0 qt/A; PHI 0d, REI 12h.  Suppression only. See label for tank mix restrictions.

Cucumber Mosaic Virus (CMV)

Many different strains of CMV occur and the host range includes plants in more than thirty-one different families. In pepper, the symptoms can be confused with tomato spotted wilt virus as well as other virus diseases and include mosaic, mottling, ring spots, stunting, and distortion. The disease is spread by several species of aphids in a nonpersistent manner, meaning that the virus does not remain in the aphids for a prolonged period of time and insecticides are therefore not useful for CMV control. Reduce weeds, especially chickweed, pokeweed, and milkweeds as much as practical. Isolate pepper fields from cucurbits and Prunus spp. (e.g., cherry trees) which are the overwintering host of the green peach aphid, especially where there has been a history of CMV.

Potato Virus Y (PVY)

PVY has a worldwide distribution. 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. Early infections can cause stunting and a decrease in fruit set. PVY is a 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 plants, legumes, and plants in the Chenopodiaceae family (e.g., spinach, chard, beets). PVY is transmitted in a non-persistent manner by more than twenty-five species of aphids and may also be transmitted mechanically by foliar contact. Long-distance transport is by winged aphids and on infected potato seed tubers. 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 are required for virus transmission. Minimize contact disease spread by minimizing mechanical damage during cultivation, spraying, and harvest. Remove virus-infected plants. Resistant cultivars are available.

Tobacco and Tomato Mosaic Virus (TMV, TomMV)

Several strains of TMV exist, including the closely related tomato (TomMV) strain. Symptoms on pepper can include yellow, chlorotic spotting, but can vary considerably as will the severity of disease and the effect on yield. Both strains can be seedborne or transferred from previously infected plant debris, weeds, transplants, other crops, or workers using tobacco products. Unlike other viruses, TMV and TomMV are easily spread from plant to plant by contact with hands and tools. Insects are not considered to be important vectors. Grow resistant varieties. Control weeds as much as practical. Do not plant susceptible peppers or tomatoes for at least two years on land that previously had TMV-infected crops. Handle plants as little as possible. Do not allow workers to use tobacco products while working with plants.

Tomato Spotted Wilt Virus (TSWV)

The host range for TSWV is one of the largest of any virus. Hundreds of plant species are susceptible including many commercial floriculture crops. Symptoms include chlorosis of leaves and blotching on green tissue. Do not raise tomato, pepper, eggplant, or cauliflower transplants in the same greenhouse as ornamentals. Monitor thrips in the greenhouse and control, as necessary. Control greenhouse weeds, as many are hosts to TSWV.