Disease Control : New England Vegetable Management Guide : UMass Amherst

NOTES: 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 Alphabetical Listing by Trade Name for more information on products with the same active ingredients.

The symbol ^OGindicates 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. 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%.

Bacterial Canker (Clavibacter michiganensis pv. michiganensis)

Initial symptoms are often a wilting and/or scorching of half of a leaf or one side of a plant. Necrotic leaf lesions up to 1/4" in diameter may appear on the upper leaf surface of mature leaves. Slightly raised white spots called “birds-eye spots” about 1/16" in diameter can appear on the fruit, usually when the green fruit in ½ to 2" in diameter. When these symptoms occur, remove the entire plant, including roots from the greenhouse. Wash hands with soap and water before handling healthy plants. There are few effective bactericides to control this disease. If extensive bacterial canker occurs in the greenhouse, steaming of the soil is advised. Pruning, harvesting and handling, especially when plants are wet, spreads the bacterium down the row. See discussion of bacterial canker on Tomato (Outdoor).

Bacillus subtilis strain QST 713 (Serenade ASO^OG): 2.0 to 4.0 qt/A; PHI 0d, REI 4h, Group BM02. See label for tank mix rates and restrictions for greenhouse use.

Gray Mold /Botrytis Blight (Botrytis cinerea)

White ring spots or “ghost spots” may appear on green fruit due to an earlier infection. Management of the environment is very important in controlling this disease. Keep humidity below 80% by heating and ventilating, especially at night. Avoid wetting the foliage during times when drying is slow. Practice strict sanitation, removing senescent tissues (drying) and infected crop debris. Pruning of lower leaves to clean-cut stubs aids in disease prevention by improving air circulation through the crop. Fungicide rotations and combinations are important because strains resistant to benlates, dichloran, captan, and iprodione have been reported.

Bacillus subtilis strain QST 713 (Cease^OG): 3.0 to 6.0 qt/100 gal/A; PHI 0d, 4 hr, Group BM02.
copper sulfate basic (Cuprofix Ultra 40 Disperss^OG): rates vary with products; REI 48h, Group M01. See label for specific rates and application methods
cyprodinil plus fludioxonil (Switch 62.5 WG): 11.0 to 14.0 oz/A; PHI 0d, REI 12h, Groups 9 & 12.
fenhexamid (Decree 50 WDG, AKA Elevate 50 WDG): 1.0 to 1.5 lb/A; PHI 0d, REI 12h, Group 17. Treated greenhouse tomatoes cannot be used for processing. See label for additional restrictions.
fludioxonil (Emblem, AKA Spirato GHN): 5.5 to 7.0 oz/A; PHI 0d, REI 12h, Group 12. Alternate with a different mode of action (FRAC group) after 2 applications.
fluopyram plus pyrimethanil (Luna Tranquility): 11.2 fl oz/A; PHI 1d, REI 12h, Groups 7 & 9. See label for specific instructions for greenhouse use.
penthiopyrad (Fontelis): 26.0 to 24.0 fl oz/A; PHI 0d, REI 12, Group 7.
polyoxin D (Affirm WDG): 6.2 oz/A; PHI 0d, REI 4h, Group 19.
potassium bicarbonate (MilStop^OG, AKA PB 133^OG): 1.25 to 5.0 lb/100 gal water; PHI 0d, REI 1h, Group NC. Use solution within 12 hours of preparation. See label for small volume application rates.
pyrimethanil (Scala SC): 7.0 fl oz/A; PHI 1d, REI 12h, Group 9. Use only in a tank mix with another effective fungicide recommended for Botrytis. Apply Scala SC only in well ventilated plastic tunnel houses or glass houses. Ventilate for at least 2 hours after application.

Late Blight (Phytophthora infestans)

Protectant fungicides are a key tool for management; however, many strains of P. infestans have become resistant to mefenoxam. When resistant strains are present, early blight fungicides will give as much protection against late blight as mefenoxam combinations. Avoid the use of overhead irrigation. Promptly incorporate old tomato crops after harvest in high tunnels; in the greenhouse remove all debris and clean greenhouse thoroughly after harvest. Eliminate cull piles and volunteer plants of both tomato and potato. Some resistant cultivars are available.

Bacillus subtilis Strain QST 713 (Cease^OG): 3.0 to 6.0 qt/A; PHI 0d, REI 4h, Group BM02.
copper hydroxide (Kocide 3000): 0.5 to 1.5 Tbsp/1000 sq ft (1lb/A); PHI 0d, REI 24h, Group M01. Do not apply in a spray solution having a pH less than 6.5.
copper soap (Camelot O^OG): 0.5 to 2.0 gal/30 to 100 gal water; PHI 1d, REI 4h, Group M01.
cyazofamid (Ranman 400SC): 2.1 to 2.75 fl oz/A; PHI 0d, REI 12, Group 21. See label for surfactant recommendations. Alternate applications with fungicides that have a different mode of action.
hydrogen dioxide plus peroxyacetic acid (Oxidate 2.0): See label for specific dilution rates; PHI 0d, REI 0h, Group NC.
mancozeb (Dithane M45): 1.5 to 2.0 lb/A; PHI 5d, REI 24h, Group M03.
mancozeb plus zoxamide (Gavel 75DF): 1.5 to 2.0 lb/A; PHI 5d, REI 48, Groups M03 & 22.
mandipropamid (Micora): 5.5 to 8.0 fl oz/A; PHI 1d, REI 4h, Group 40. For tomato late blight only. Do not make more than 2 consecutive applications. See label for surfactant recommendation. Not for use in Maine.
mandipropamid plus difenoconazole (Revus Top): 5.5 to 7.0 fl oz/A; PHI 1d, REI 12, Groups 3 & 40.
oxathiapipprolin plus mandipropamid (Orondis Ultra): 5.5 to 8.0 fl oz/A; PHI 1d, REI 4h, Groups 49 & 40. See label for application methods and restrictions. Not for use in greenhouse on any other crop.
phosphorous acid (K-Phite 7LP): See label for rates; PHI 0d, REI 4h, Group P07. See label for application instructions and rates (ground and aerial).

Leaf Mold (Passalora fulva)

This disease occurs in both soil or hydroponic production and is most important in poorly ventilated plastic greenhouses. The pathogen produces large numbers of conidia on infected tissue; the disease can spread rapidly throughout a greenhouse by air currents, water, insects, and workers. Start with certified disease free seed. Use resistant cultivars. Improve air circulation by adequate row/plant spacings and removal of lower leaves. Avoid the formation of water droplets on leaves by watering in the morning. Reduce relative humidity by a combination of heating and venting, especially at night. Avoid excessive nitrogen fertilization. Remove diseased leaves and destroy. At the end of crop cycle, remove and destroy all plant residue.

copper hydroxide (Kocide 3000): 0.5 to 1.5 Tbsp/1000 sq ft (1 lb/A); PHI 0d, REI 24h, Group M01. Do not apply in a spray solution having a pH less than 6.5 or tank mix with Aliette.
famoxadone plus cymoxanil (Tanos): 8.0 oz/A; PHI 3d, REI 12h, Groups 11 & 27.
mancozeb (Dithane M45): 1.5 to 2.0 lb/A; PHI 5d, REI 24h, Group M03.
mancozeb plus zoxamide (Gavel 75DF): 1.5 to 2.0 lb/A; PHI 5d, REI 48h, Groups M03 & 22.
mandipropamid plus difenoconazole (Revus Top): 5.5 to 7.0 fl oz/A; PHI 1d, REI 12h, Groups 3 & 40.
polyoxin D (OSO 5%^OG): 6.5 to 13.0 fl oz/A; PHI 0d, REI 4h, Group 19.

**Pith Necrosis (Pseudomanas corrugata)**

This disease typically occurs in early planted tomatoes growing when night temperatures are cool, humidity levels are high, and when plants are growing vigorously because of excessive levels of nitrogen. The disease is associated with prolonged periods of cloudy, cool weather. Symptoms consist of yellowing and wilting of young leaves. Serious infections result in yellowing or wilting of upper portions of plants with brown to black lesions on infected stems and petioles. When stems are cut longitudinally, the center of the stem (pith) may be extensively discolored, hollow, and/or degraded. Stems may be swollen, numerous adventitious roots can form, and infected stems may shrink, crack, and collapse. Preventive measures to minimize the occurrence of this disease in high tunnels include adequate ventilation to avoid high humidity levels, avoiding excessive nitrogen levels to prevent vigorous plant growth, incorporation of crop debris to speed decomposition of residue and associated bacteria, and crop rotation.

Powdery Mildew (Oidium neolycopersici)

Powdery mildew of tomato is emerging as an important disease of greenhouse crops. This pathogen is favored by low light and cool temperatures. In contrast to other fungal plant pathogens, it does not require free water to germinate and cause disease. DeRuiter's Seeds has recently released the cultivar Grace which has resistance to powdery mildew.

Bacillus pumilus strain QST2808 (Sonata ASO^OG): 2.0 to 4.0 qt/100 gal of spray mix; PHI 0d, REI 3h, Group BM02. For disease suppression only (in greenhouse use).
Bacillus subtilis strain QST 713 (Cease^OG): 3.0 to 6.0 qt/A; PHI 0d, REI 4 hr, Group BM02.
cyprodinil plus fludioxonil (Switch 6.25 WG): 11.0 to 14.0 oz/A; PHI 0d, REI 12h, Groups 9 & 12. Do not apply to small tomatoes such as cherry or grape in the greenhouse.
fludioxonil (Emblem, AKA Spirato GHN): 5.5 to 7.0 oz/A. PHI 0d, REI 12h, Group 12. Alternate with a different mode of action (FRAC group) after 2 applications of Emblem.
fluopyram plus pyrimethanil (Luna Tranquility): 11.2 fl oz/A; PHI 0d, REI 12h, Groups 7 & 9. See label for specific instructions for greenhouse use.
paraffinic oil (JMS Stylet-Oil): 3.0 to 6.0 qt/100 gal water; PHI 0d, REI 4h, Group NC. Spray for thorough coverage of upper leaf surface.
penthiopyrad (Fontelis): 16.0 to 24.0 fl oz/A; PHI 0d, REI 12, Group 7.
phosphorous acid (K-Phite 7LP): See label for rates; PHI 0d, REI 4h, Group P07.
polyoxin D (Affirm WDG): 6.2 fl oz/A; PHI 0d, REI 4h, Group 19. See label for restrictions.
potassium bicarbonate (MilStop^OG, AKA PB 133): 1.25 to 5.0 lb/100 gal water; PHI 0d, REI 1h, Group NC. Use solution within 12 hours of preparation. See label for specific rates and restrictions.
potassium salts of fatty acids (M-Pede^OG): See label for rates; PHI 0d, REI 12h, Group NC. See label for precautions.
mandipropamid + difenoconazole (Revus Top): 5.5 to 7.0 fl oz/A; PHI 1d, REI 12, Groups 3 & 40.
sulphur (Microthiol Disperss^OG): 5.0 to 20 lb/A; PHI 0d, REI 24h, Group M02. Do not use within 2 weeks of an oil spray treatment. Crops grown in greenhouses may be much more sensitive to sulfur injury. Do not use if temperature will exceed 90ºF within 3 days following spraying.
triflumizole (Trionic 4 SC): 2.0 to 4.0 fl oz/100 gal.; PHI 1d, REI 12h, Group 3. Apply only as foliar spray. See label for surfactant recommendation.

Soilborne Diseases

Several fungi including Rhizoctonia, Pythium, Phytophthora, Colletotrichum, Verticillium, Sclerotinia, and Fusarium, in addition to the bacterium that causes tomato canker, and root knot nematodes may become established in greenhouse soils or survive in tomato roots left from a previous crop. White rot (Sclerotinia) on stems occurs erratically during moist, cool periods in the spring. Distribution of diseased plants in a greenhouse is random but is often associated with low spots. Plants of all ages are susceptible. The pathogen produces hardened black fungal survival structures called sclerotia that can survive several years in the soil. Cut the plant off at the base and remove from the greenhouse. Depending on which pathogen is present, rotation or the use of resistant varieties in addition to the use of grafted plants with vigorous rootstocks may be viable alternatives. Otherwise, steam or chemical treatment of the soil is necessary. It should be considered, however, that treatment of soil may not entirely eliminate the pathogens and, in the case of Pythium, Rhizoctonia, and Fusarium, the pathogens may rapidly recolonize the soil. There is no effective chemical treatment for the wilt and decline diseases caused by Verticillium and Fusarium. The most effective management techniques are resistant cultivars and sanitation, including soil pasteurization. (NOTE: the current Bayer label for Coniothyrium minitans (Contans) does not include tomato).

Bacillus subtilis strain QST 713 (Serenade ASO^OG): 0.1 to 3.0 fl oz/100 lb seed; PHI 0d, REI 4h, Group BM02. See label for tank mix rates and restrictions for greenhouse use.
Coniothyrium minitans (Contans WG^OG): See label for rates; PHI 0d, REI 4h, Group BM02. Spray on the soil surface and incorporate into the top 2" of the soil. See label for additional application instructions and restrictions.
cyazofamid (Ranman 400 SC): Pythium ONLY. 3.0 fl oz/100 gal water; PHI 0d, REI 12h, Group 21. Use as a soil drench. For tomato transplants only.
Gliocladium catenulatum, aka Clonostachys rosea, strain J1446 (P-Vent^OG): See label for rates and application instructions; PHI 0d, REI 4h, Group BM02.
phosphorous acid (K-Phite 7LP): see label for rates and application methods; PHI 0d, REI 4h, Group P07.
propamocarb HCl (Previcur Flex): Pythium and Phytophthora species ONLY. See label for rates; PHI 2d, REI 12h, Group 28. Prevent intense sunlight after application by applying Previcur Flex in the evening. Do not apply to dry rockwool or other dry growing media without first pre-wetting with water.
Streptomyces sp. strain K61 (MycoStop^OG): See label for specific uses and rates; PHI 0d, REI 4h, Group BM02.
Streptomyces lydicus WYEC 108 (Actinovate AG^OG): 3.0 to 12.0 oz/A (soil drench); PHI 0d, REI 4h, Group BM02.
Trichoderma asperellumI (ICC 012) and T. gamsii (ICC 080) (Bio-Tam 2.0^OG, AKA Bioten WP): See label for use and rates; REI 4h, Group BM02.

Tomato Gray Leaf Spot (Stemphylium lycopersici, S. solani, and S. botryosum)

See the Disease Control section in Tomato, Outdoor for more information about this disease.

azoxystrobin plus difenoconazole (Quadris Top): 8.0 fl oz/A; PHI 0d, REI 12h, Group 11&3. See label for restrictions.
chlorothalonil (Echo 720):1.38 to 2.0 pt/A; PHI 0d, REI 12h, Group M05. Apply in sufficient water to obtain adequate coverage. Begin applications when dew or rain occur, and disease threatens.
chlorothalonil plus mefenoxam (Ridomil Gold Bravo SC): 2.5pt/A; PHI 7d, REI 48h, Group M05&4. Begin preventive applications early when conditions are favorable for disease. See label for additional restrictions.
chlorothalonil plus oxathiapiprolin (Orondis Opti (Premix): 1.75 to 2.5 pt/A; PHI 0d, REI 12h, Group M05&49. See label for warnings and restrictions.
chlorothalonil plus zoxamide (Zing!): 36 fl oz/A; PHI 5d, REI 12h, Group M05&22. See label for warnings and restrictions.
copper hydroxide (Nu-Cop 50WPOG): 1.0 lb/A; PHI 1d, REI 48h, Group M01. May be used in greenhouse. See label for warnings and restrictions.
difenoconazole plus benzovindiflupyr (Aprovia Top): 10.5 to 13.5 fl oz/A; PHI 0d, REI 12h, Group 3&7. See label for warnings and restrictions.
difenoconazole plus cyprodinil (Inspire Super): 16.0 to 20.0 fl oz/A; PHI 0d, REI 12h, Group 3&9. Do not make more than 2 consecutive applications before alternating to a non- Group 7 fungicide. Use of a spreading adjuvant is recommended.
difenoconazole plus fluopyram (Luna Flex): 10.0 to 13.6 fl oz/A; PHI 0d, REI 12h, Group 3&7. See label for warnings and restrictions.
fluopyram plus pyrimethanil (Luna Tranquility): 11.2 fl oz/A; PHI 1d, REI 12h, Group 7&19. May be used in greenhouse. See label for application restrictions.
mancozeb (Dithane F-45 Rainshield): 1.2 to 2.4 qt/A; PHI 5d, REI 24h, Group M03. Start applications when seedlings emerge, or transplants are set. See label for additional restrictions.
mancozeb plus copper (ManKocide): 1.75 to 3.0 lb/A; PHI 5d, REI 24 or 48h, Group M03&M01. May be used in greenhouse. See label for application warnings and restrictions.
mancozeb plus zoxamide (Gavel 75DF): 1.5 to 2.0 lb/A; PHI 5d, REI 48h, Group M03&22. See label for restrictions.
mandipropamid plus difenoconazole (Revus Top): 5.5 to 7.0 fl oz/A; PHI 1d, REI 12h, Group 3&40. Begin applications prior to disease development. Do not make more than 2 sequential applications before alternating to a different mode of action. See label for additional restrictions.
tetraconazole (Mettle 125ME): 6.0 to 8.0 fl oz/A; PHI 0d, REI 12h, Group 3. See label for restrictions.
trifloxystrobin (Flint): 4.0 oz/A; PHI 0d, REI 12h, Group 11. Begin applications preventively. See label for application restrictions.

Viruses

See Tomato (Outdoor) for a discussion on viruses.

Disease Control