Disease Control

NOTES: 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 26 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 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 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.

Anthracnose (Colletotrichum), Alternaria Leaf Spot, and Black Rot (Didymella)

Anthracnose symptoms appear on cucurbits as circular, water-soaked leaf spots. These eventually turn yellow/tan and can become brown and necrotic. Alternaria symtooms first appear on older leaves near the crown. Lesions are small, yellow-brown, and have a characteristic yellow halo around the infected spots. Black rot symptoms usually appear after harvest as small dark watery lesions on the fruit surface. Black fruiting bodies from the fungus can typically be seen on the fruit and appear as black specks. Plant only certified disease-free seed. Rotate out of cucurbits for at least 2 years. Control all weeds, especially volunteer cucurbits. Collect and burn or plow down deeply all infected crop debris after harvest. Grow cultivars with resistance if available. Avoid wounding fruit during harvesting. Immerse fruit in clean and fresh water containing a post-harvest sanitizer. Chemical control can be obtained through a regular spray program of targeted and protective fungicides. Coverage of leaf undersides and fruit is crucial to success.

azoxystrobin (Quadris): 11.0 to 15.5 fl oz/A; PHI 1d, REI 4h, Group 11. Do not rotate with other Group 11 fungicides.

azoxystrobin plus chlorothalonil (Quadris Opti): 3.2 pt/A; PHI 1d, REI 12h, Groups 11 & M05.  See label for tank mix precautions.  

azoxystrobin plus difenoconazole (Quadris Top): 10.0 to 14.0 fl oz/A; PHI 1d, REI 12h, Groups 11 & 3.

boscalid (Endura): 6.5 oz/A; PHI 0d, REI 12h, Group 7. Not labeled for anthracnose.

chlorothalonil (Bravo Weather Stik): 1.5 to 3.0 pt/A; PHI 0d, REI 12h, Group M05. Bravo WS can cause injury to watermelon fruit; see label.

copper hydroxide (Kocide 3000OG): 0.5 to 1.25 lb/A; PHI 0d, REI 48h, Group M01. Do not apply in a spray solution having a pH of less than 6.5 or tank mix with Aliette.

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

difenoconazole plus cyprodinil (Inspire Super): 16.0 to 20.0 fl oz/A; PHI 7d, REI 12h, Group 3 & 9. Apply in sufficient volume to achieve thorough coverage.

famoxadone plus cymoxanil (Tanos): 8.0 oz/A; PHI 3d, REI 12h, Groups 11 & 27. Tank mix with an appropriate contact fungicide with a different mode of action. Not labeled for black rot.

fenamidone (Reason 500 SC): 5.5 fl oz/A; PHI 14d, REI 12h, Group 11. Do not rotate with other Group 11 fungicides. For Alternaria only.

fluopyram plus tebuconazole (Luna Experience): 6.0 to 17.0 fl oz/A; PHI 7d, REI 12h, Groups 7 & 3. Watermelon only.

mancozeb (Dithane F45): 1.6 to 2.4 qt/A; PHI 5d, REI 24h, Group M03. Some cantaloupe varieties are sensitive.

mancozeb plus copper hydroxide (ManKocide): 2.0 to 3.0 lb/A; PHI 5d, REI 48h, Groups M03 & M01. 

penthiopyrad (Fontelis): 12.0 to 16.0 fl oz/A; PHI 1d, REI 12h, Group 7. Not labeled for anthracnose.

polyoxin D (OSO 5%SCOG): 6.5 to 13.0 fl oz/A; PHI 0d, REI 4h, Group 19.

potassium bicarbonate (MilStopOG): 2.0 to 5.0 lb/100 gal/A; PHI 0d, REI 1h, Group NC. See label for small volume application rates.

pyraclostrobin (Cabrio EG): 12.0 to 16.0 oz/A; PHI 0d, REI 12h, Group 11.

pyraclostrobin plus boscalid (Pristine): 12.5 to 18.5 oz/A; PHI 0d, REI 12h, Groups 11 &7. Do not make more than one application of Pristine before alternating with a non-Group 11 fungicide.

thiophanate methyl (Topsin M 70WP): For anthracnose and black rot only, 0.5 lb/A; PHI 1d, REI 24h, Group 1. The repeated exclusive use of Topsin M may lead to buildup of resistant strains of fungi and loss of disease control.

Downy Mildew (Pseudoperonospora cubensis)

Pseudoperonospora cubensis infects only members of the cucurbit family and is an obligate parasite. Its survival depends on the presence of living cucurbit hosts, either in climates which permit their growth year round or in greenhouse culture. The source of primary inoculum in cold climates is windblown sporangia from areas where plants survive the cold season. Generally, downy mildew of cucurbits does not arrive in southern New England until September. However, in some seasons it can move up the eastern seaboard early and arrive in July. The progress of downy mildew is tracked by the North American Plant Disease Forecast Center and warnings issued based on disease progression and weather (http://cdm.ipmpipe.org/). Symptoms of downy mildew include small angular lesions on the leaves which stay confined to the veins. These lesions later develop into darker necrotic spots and can often times have grey fuzzy fungal growth under leaves. Physiological specialization occurs in P. cubensis and at least 5 pathotypes have been described. Cucumber and melon are susceptible to all pathotypes, while squash and pumpkin cultivars vary in their reactions. Spread of downy mildew can occur over long distances by air currents and moves within a field via wind-dispersed sporangia. The main means of control are fungicide applications, the use of resistant cultivars, and cultural practices. Maximum control can be achieved only with a combination of these measures.

Some commercial cultivars of cucumber have good levels of resistance to downy mildew. Watermelon and melon cultivars are available with low levels of resistance. Squash and pumpkin cultivars are resistant to some pathotypes and outbreaks of non-resistant pathotypes do not usually occur in New ENgland until very late in the season, typically causing minimal yield losses.

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

azoxystrobin plus chlorothalonil (Quadris Opti): 3.2 pt/A; PHI 1d, REI 12h, Groups 11 & M05. See label for tank mix precautions.     

Bacillus amyloliquefaciens strain D747 (DoubleNickelOG): 0.25 to 3.0 lb/A; PHI 0d, REI 4 h, Group BM02. Disease suppression only. For improved control; mix or rotate with a chemical fungicide.

chlorothalonil (Bravo Weather Stik): 1.5 to 2.0 pt/A; PHI 0d, REI 12h, Group M05.

copper hydroxide (Kocide 3000OG): 0.5 to 1.25 lb/A; PHI 0d, REI 48h, Group M01. Do not apply in a spray solution having a pH of less than 6.5 or tank mix with Aliette.

cyazofamid (Ranman 400 SC): 2.1 to 2.75 fl oz/A; PHI 0d, REI 12h, Group 21. Alternate sprays of Ranman with a fungicide with a different mode of action.

cymoxanil (Curzate 60 DF): 3.2 to 5.0 oz/A; PHI 3d, REI 12h, Group 27. Use only in combination of a labeled rate of a protectant fungicide (copper, chlorothalonil, mancozeb).

dimethomorph (Forum): 6.0 fl oz/A; PHI 0d, REI 12h, Group 40. Apply only in combination with a labeled rate of another non-group 40 fungicide. Do not make more than 2 sequential applications of Forum before alternating to a fungicide with a different mode of action.

famoxadone plus cymoxanil (Tanos): 8.0 oz/A; PHI 3d, REI 12h, Groups 11 & 27. Tank mix with an appropriate contact fungicide with a different mode of action.

fenamidone (Reason 500 SC): 5.5 fl oz/A; PHI 14d, REI 12h, Group 11. Do not rotate with other Group 11 fungicides.

fluazinam (Omega 500F): 12.0 to 24.0 fl oz/A; PHI 7d and 30d (see label), REI 12h, Group 29. See label for restrictions. 

fluopicolide (Presidio 4SC): 3.0 to 4.0 fl oz/A; PHI 2d, REI 12h, Group 43. A tank mix with another labeled fungicide with a different mode of action (FRAC #) must be used for resistance management.

fosetyl- Al (Aliette WDG): 2.0 to 5.0 lb/A; PHI 12d, REI 24h, Group P7. Do not tank mix with copper products or apply in a spray solution with a pH less than 6.0.

mancozeb (Dithane F45): 1.6 to 2.4 qt/A; PHI 5d, REI 24h, Group M03.

mancozeb plus copper hydroxide (ManKocide): 2.0 to 3.0 lb/A; PHI 5d, REI 48h, Groups M03 & M01.

mancozeb plus zoxamide (Gavel 75DF): 1.5 to 2.0 lb/A; PHI 5d, REI 48h, Groups M03 & 22. Apply preventively to control downy mildew. Do not tank mix with other fungicides if the target pest is only downy mildew.

oxathiapiprolin (Orondis Ultra): 5.5 to 8.0 fl.oz/A; PHI 0d, REI 4h, Group 49 & 40. Begin foliar application prior to disease development. Use higher rate when disease is present.

phosphorous acid  (Fosphite): 1.0 to 3.0 qt/20.0 gal (foliar); PHI 0d, REI 4h, Group P07. Do not apply to plants that are heat or moisture stressed. Do not apply directly to copper treated plants within 20-day interval to avoid plant injury. See label for other application methods and additional restrictions.

propamocarb HCl (Previcur Flex): 1.2 pt/A; PHI 2d, REI 12h, Group 28. Alternate with a contact fungicide (copper, chlorothalonil, sulfur).

Reynoutria sachalinensis extract (RegaliaOG): 1.0 to 4.0 qt/A; PHI 0d, REI 4h, Group P5. Apply to ensure thorough coverage. See label for specific application methods and restrictions 

zoxamide + chlorothalonil (Zing!): 30.0 to 36.0 fl oz/A; PHI 0d, REI 12h, Groups 22 & M05.

Phytophthora Blight and Fruit Rot

Symptoms of this disease can occur at any stage of development. In seedlings symptoms are characteristic of damping off. On vines it appears as water-soaked lesions that become dark and later girdle the stems causing collapse and foliage death. On the foliage, symptoms include chlorosis, water-soaked lesions, and leaf death. Lesions will usually begin as small spots and quickly become necrotic with an olive green border around the spots. Phytophthora capsici cannot be managed by fungicide applications alone; successful disease control is achieved only by a season-long effort to manage water and other cultural practices. The single most effective way to control this disease is to prevent its movement into clean fields by equipment, humans, or infested water. Plant susceptible crops (tomatoes, peppers, eggplant, all cucurbit species, and beans) in fields that have no history of this disease and are well-drained. Plant non-vining crops on raised beds, avoid planting in low areas where water puddles, and improve drainage by sub-soiling. Promptly disk under small areas where the disease appears along with a border of healthy appearing plants. Avoid working in wet fields and minimize compaction.

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

cyazofamid (Ranman 400 SC): 2.75 fl oz/A; PHI 0d, REI 12h, Group 21. Addition of a surfactant improves effectiveness when disease pressure is severe. Alternate sprays of Ranman with a fungicide with a different mode of action. Observe a 30-day plant back interval for crops not on label.

dimethomorph (Forum): 6.0 fl oz/A; PHI 0d, REI 12h, Group 40. Apply only in combination with a labeled rate of another non-group 40 fungicide. Do not make more than 2 sequential applications of Forum before alternating to a fungicide with a different mode of action.

famoxadone plus cymoxanil (Tanos): 8.0 to 10.0 oz/A; PHI 3d, REI 12h, Groups 11 & 27. Suppression ONLY.  Foliar or fruit phase ONLY. Tank mix with an appropriate contact fungicide. Do not alternate with other Group 11 fungicides.

fluazinam (Omega 500F): 12.0 to 24.0 fl oz/A; PHI 7d & 30d (see label), REI 12h, Group 29. See label for restrictions. 

fluopicolide (Presidio 4SC): 3.0 to 4.0 fl oz/A; PHI 2d, REI 12h, Group 43. A tank mix with another labeled fungicide with a different mode of action is required.

fosetyl Al (Aliette WDG): 2.0 to 5.0 lb/A; PHI 12d, REI 24h, Group P7. Do not tank mix with copper compounds. Mixing Aliette with surfactants or foliar fertilizers is not recommended. Use the high rate when Phytophthora blight is active.

oxathiapiprolin (Orondis Ultra): 5.5 to 8.0 fl.oz/A; PHI 0d, REI 4h, Groups 49 & 40. Begin foliar application prior to disease development.

phosphorous acid (Fosphite): 1.0 to 3.0 qt/20.0 gal (foliar); PHI 0d, REI 4h, Group P7. Do not apply to plants that are heat or moisture stressed. Do not apply directly to copper treated plants within 20-day interval to avoid plant injury. See label for other application methods and additional restrictions. 

Reynoutria sachalinensis extract (RegaliaOG): 1.0 to 4.0 qt/A; PHI 0d, REI 4h, Group P5. Apply to ensure thorough coverage. See label for specific application methods and restrictions.

Powdery Mildew (Podosphaera xanthii)

Powdery mildew infections are very characteristic to its name. Symptoms of this disease first appear as pale yellow leaf spots. As the disease progresses these spots develop into powdery, white patches across the bottom and top of the leaf surface. Unlike downy mildew, the symptoms of this disease are not confined to the veins of the foliage and can spread over any part of the plant. Older plants are typically affected first. Fungicides should be applied at the first sign of disease (or earlier with some products). Begin scouting for powdery mildew at fruit initiation. On cucurbits, powdery mildew fungi attack both the top and bottom of the leaf, and this makes the disease more difficult to control with non-systemic fungicides. However, powdery mildew fungi tend to become resistant to systemic fungicides such as Topsin-M (Group 1); Cabrio, Flint Extra, Quadris and Sovran (Group 11). Resistance to Group1 and Group 11 fungicides have resulted in the removal of these classes of fungicides from recommendations, with the exception of Pristine which is a combination product. Resistance to the DMI fungicides (Group 3, e.g. Rally, Procure) is also widespread; use these products at the high labeled rate only. The most effective contact fungicides are sulfur, mineral oil, and chlorothalonil. Begin applying fungicides when powdery mildew is at a low level (threshold is 1 of 50 old leaves with symptoms on either leaf surface; do not begin using mobile fungicides when disease is widespread. A seven-day interval is recommended once disease is observed.

Bacillus amyloliquefaciens strain D747 (DoubleNickelOG): 0.25 to 3.0 lb/A; PHI 0d, REI 4 h, Group BM02. Disease suppression only. For improved control; mix or rotate with a chemical fungicide.

boscalid (Endura): 6.5 oz/A; PHI 0d, REI 12h, Group 7. Suppression only.

botanical extract (EcoswingOG): 1.5 to 5.0 pt/A; PHI 0d, REI 4h, Group BM01. 

chlorothalonil (Bravo Weather Stik): 2.0 to 3.0 pt/A; PHI 0d, REI 12h, Group M05. Use caution when applying to watermelon. See label for restrictions.

copper hydroxide (Kocide 3000OG): 0.5 to 1.25 lb/A; PHI 0d, REI 48h, Group M01. Do not apply in a spray solution having a pH less than 6.5 or tank mix with Aliette.

cyprodinil plus fludioxonil (Switch 62.55 WG): 11.0 to 14.0 oz/A; PHI 1d, REI 12h, Groups 9 & 12.

cyflufenamid (Torino): 1.7 to 3.4 oz/A; PHI 0d, REI 4h, Group U6. 

difenoconazole plus cyprodinil (Inspire Super): 16.0 to 20.0 fl oz/A; PHI 7d, REI 12h, Groups 3 & 9.

fluopyram plus tebuconazole (Luna Experience): 6.0 to 17.0 fl oz/A; PHI 7d, REI 12h, Groups 7 & 3. Watermelon only.

flutriafol (Rhyme 2.08 SC): 5.0 to 7.0 fl oz/A; PHI 0d, REI 12h, Group 3.

mineral oil (JMS Stylet-oilOG): 3.0 to 6.0 qt/100.0 gal; PHI 0d, REI 4h, Group NC.

metrafenone (Vivando): 10.3 to 15.4 fl oz/A; PHI 0d, REI 12h, Group 50.

potasium dihydrogen phosphate (Nutrol): 10.0 to 20.0 lb/A; PHI 0d, REI 4h, Group P7.

myclobutanil (Rally 40 WSP): 2.5 to 5.0 oz/A; PHI 0d, REI 24h, Group 3.

penthiopyrad (Fontelis): 12.0 to 16.0 fl oz/A; PHI 1d, REI 12h, Group 7.

polyoxin D (OSO 5%SCOG): 6.5 to 13.0 fl oz/A; PHI 0d, REI 4h, Group 19.

potassium bicarbonate (KaligreenOG): 2.5 to 5.0 lb/A; PHI 1d, REI 4h, Group NC. Not labeled for muskmelon. See label. 

quinoxyfen (Quintec): 4.0 to 6.0 fl oz/A; PHI 3d, REI 12h, Group 13. Melon only. Alternate with other effective fungicides at their recommended rates and spray intervals.

sulfur (Microthiol DisperssOG): 2.0 to 4.0 lb/A; PHI 0d, REI 24h, Group M02. Sulfur can injure plants, especially when temperatures reach 90° F. Do not apply to sulfur sensitive varieties.

triflumizole (Procure 480SC): 4.0 to 8.0 oz/A; PHI 0d, REI 12h, Group 3. Alternate with a protectant fungicide (copper, chlorothalonil, mancozeb, sulfur).

triflumizole (Trionic 4 SC): 4.0 to 8.0 fl oz/100 gal.; PHI 1d, REI 12, Group 3. Apply only as foliar spray. See label for surfactant recommendation. Labeled for greenhouse use.

Scab (Cladosporium cucumerinum)

Scab is a significant problem for summer and winter squash, pumpkin, melon, and watermelon. Symptoms of this disease appear on both the foliage and fruit. On foliage, symptoms are greyish brown lesions with a yellow halo. Depending on the severity of infection, the disease can also cause leaf deformation. Fruit symptoms appear small at first and can grow into larger, dark pockmarks. As the disease progresses, lesions on fruit can grow together and become entry points for secondary infections. Resistant cultivars of cucumber are widely available. The pathogen can live on infected crop debris on or in the soil and may be seedborne. Rotate with non-cucurbit crops for 2 to 3 years. Select sites with well-drained soil and good air movement for rapid drying of foliage and fruit. Avoid overhead irrigation and dense plant canopies. Fungicide sprays may not be effective during extended cool, wet weather due to the short disease cycle of this pathogen.

acibenzolar-S-methyl (Actigard 50 WG): 0.5 to 2.0 oz/A; PHI 0d, REI 12 h, Group P1. For surpression only. 

chlorothalonil (Bravo Weather Stik): 2.0 to 3.0 lb/A; PHI 0d, REI 12h, Group M05. Use caution when applying to watermelon. See label for restrictions.

mancozeb (Dithane F45): 1.6 to 2.4 qt/A; PHI 5d, REI 24h, Group M03.

mancozeb plus copper hydroxide (ManKocide): 2.0 to 3.0 lb/A; PHI 5d, REI 48h, Groups M03 & M01. 

polyoxin D (OSO 5%SCOG): 6.5 to 13.0 fl oz/A; PHI 0d, REI 4h, Group 19.

Seed Decay

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

Bacillus amyloliquefaciens strain D747 (DoubleNickelOG): 0.01 to 0.4  fl oz/100,000 seeds; PHI 0d, REI 4h, Group BM02. 

fludioxonil (Maxim 4 FS): 0.08 to 0.16 fl oz/100 lb seed; REI 12h, Group 12. For protection against seed and soil-borne fungi.

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

thiram (Thiram SC): 4.5 fl oz/100 lb seed; REI 24h, Group M03.

Angular Leaf Spot (Pseudomonas syringae pv. lachrymans)

The symptoms of angular leaf spot appear as small, angular brown spots with a yellow halo on the foliage. Leaf spots eventually dry out and fall through leaving holes in the leaves. Spots are typically confined to the veins of the leaves, giving infected plants the characteristic angular spots. On fruit, lesions are small, tan, and appear water-soaked. Fruit is later affected by soft rot as the disease progresses and can consume the entire fruit. Avoid working in the fields when the foliage is wet. Plow crop residue under promptly after harvest to aid decomposition. Rotate out of cucurbits for 2 years. Plant resistant varieties when possible. Use pathogen-free seed or treat with hot-water to kill the bacterium in the seed. Sprays may not be effective if applied too late or if environmental conditions are conducive to spread of the disease.

copper hydroxide (Kocide 3000OG): 0.5 to 1.25 lb/A; PHI 0d, REI 48h, Group M01.  Do not apply in a spray solution having a pH less than 6.5. or tank mix with Aliette.

mancozeb plus copper hydroxide (ManKocide): 2.0 to 3.0 lb/A; PHI 5d, REI 48h, Groups M03 & M01.  

Bacterial Wilt (Erwinia tracheiphila)

Bacterial wilt is transmitted by cucumber beetles. Symptoms of this disease cause foliage to become a dull green and wilt during the day, recovering at night. As the disease progresses, leaves eventually turn yellow and brown at the margins and die back. Cucumber and muskmelon are highly susceptible to wilt; watermelon is not. Seedlings at the cotyledon and 1- to 3-leaf stage are more susceptible to infection with bacterial wilt than older plants. Thus, it is especially important to keep beetle numbers low before the 5-leaf stage. Cucumber beetles must be controlled by appropriate insecticide programs. Please refer to the information on cucumber beetle for management recommendations. Use crop rotation to reduce beetle numbers. Because this bacterium is transmitted systemically by cucumber beetles, bactericide sprays are not effective. 

Cucumber Mosaic Virus (CMV)

Many different strains of this virus occur and the host range includes plants in more than 31 different families. Many weed species also serve as hosts and the virus is seedborne in chickweed.  Symptoms of infection include stunting, yellow leaf spots, vein yellowing, malformation of leaves, and a mosaic pattern of light and dark green on leaves. On fruit, the viral symptoms appear as ring-spots or line patterns. The virus is spread by more than 40 species of aphids and 2 beetles. Seed transmission is possible but unlikely in commercial cucumber seed. The abundance of other host plants, their proximity to crops, and the presence of vectors govern the incidence and severity of disease. The use of resistant varieties is the most effective means of control. Reduce weeds, especially chickweed, pokeweed and milkweed, as much as practical. Practice rotation and plant away from previously contaminated fields. Insecticides are not effective.

Watermelon Mosaic Virus (WMV) and Papaya Ringspot Virus (PRSV-W)

Several aphid species transmit these 2 viruses. PRSV-W is only known to occur in the cucurbit family but WMV has been reported from alfalfa, vetch, crimson clover, sour clover, snow-on-the-mountain and mallow. Seed transmission is considered a possibility but remains unproven. Symptoms of this virus include stunted growth, leaf malformation, mottling and marginal chlorosis. On fruit, symptoms appear as mottling and bumpy warts or blister-like areas. 

Zucchini Yellow Mosaic Virus (ZYMV)

Zucchini Yellow Mosaic Virus was first discovered in the United States in the early 1980s. Two strains, Connecticut and Florida, are currently recognized. The Connecticut strain produces more severe symptoms than the Florida strain. Symptoms include severe malformation, blisters, necrosis, and severe plant stunting. On the fruit, the virus causes knobby areas and prominent deformation. The virus is transmitted in a no persistent manner by aphids. At this time, no weed hosts have been identified. Resistant varieties are now available.