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.

Anthracnose (Colletotrichum), Alternaria, and Black Rot (Stagonosporopsis spp. formerly Didymella bryoniae)

Do not plant winter squash or pumpkins for at least two years in fields where these diseases have been a problem. Plow under plant debris after harvest. Reduce weeds to allow for faster drying of plant surfaces. Start with certified disease-free seed. Carefully scout transplants in greenhouse for diseased plants and remove them, improve ventilation in greenhouse, and reduce overhead irrigation. Avoid injuring fruit before or during harvest. Apply protectant fungicides according to a disease forecasting system (Melcast). Black rot, also known as gummy stem blight (GSB) is one of the most destructive diseases of winter squash and pumpkins and is characterized by a distinctive black decay of the fruits of all cucurbits. Foliar symptoms start as marginal necrosis followed by larger, wedged shaped necrotic areas, often with a yellow halo. Stem cankers develop in the cortical tissue and a brown, gummy exudate is produced. Small fruiting bodies may appear as black specks in diseased tissue. Stems may be girdled on seedlings and the plant dies, or on older plants stem cankers lead to wilt and decline. Small, water-soaked spots develop on fruit, enlarge, and exude gummy material and contain many black, fruiting bodies. Black rot on butternut may appear as a superficial hardened tan to white area which can develop concentric rings. This typically occurs where the fruit touched the soil. Lesions may become hardened and dormant on mature fruit that is cured and stored under proper conditions, but chilling injury or high humidity may activate the disease and cause fruit collapse during storage. Check fruit weekly for signs of black rot. Cultivars with resistance to Anthracnose are available.

azoxystrobin (Quadris F): 11.0 to 15.5 fl oz/A; PHI 1d, REI 4h, Group 11. Do not alternate with other Group 11 fungicides. Resistant isolates of Black Rot (Stagonosporopsis) have been reported. See label for application methods and mixing instructions.
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): 12.0 to14.0 fl oz/A; PHI 1d, REI 12h, Groups 11 & 3.
Bacillus mycoides Isolate J (LifeGard WG^OG): 4.5 oz/100 gal water; PHI 0d, REI 4h, Group P06. See label for application methods and instructions. Labeled only for GSB and anthracnose.
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 mixing precautions.
boscalid (Endura): 6.5 oz/A; PHI 0d, REI 12h, Group 7.
chlorothalonil (BravoWeather Stik): 1.5 to 3.0 pt/A; PHI 0d, REI 12h, Group M05. Bravo can cause injury to watermelon fruit; see label. Rates vary for each disease; see label. For other products, see labels.
chlorothalonil plus oxathiapiprolin (Orondis Opti): 1.7 to 2.5 pt/A; PHI 0d, REI 12h, Groups M05 & 49. For enhanced control of leaf spots and other non-Oomycete diseases listed, add a chlorothalonil containing product to the spray mixture. See label.
chlorothalonil plus potassium phosphite (Catamaran): 4.0 to 6.0 pt/A; PHI 1d, REI 12, Groups M05 & P07. Do not apply under certain weather conditions (drought and conducive to sunburn); see label
copper compound (Champ 2F): 1.33 pt/A; PHI 0d, REI 48h, Group M01. Label varies with manufacturer and formulation. REI for products ranges from 4 to 48 hr.
cyprodinil plus fludioxonil (Switch 6.25 WG): 11.0 to14.0 oz/A; PHI 1d, REI 12h, Groups 9 & 12. Labeled for only black rot and Alternaria. Good coverage is essential for good disease control. Use a minimum of 10 gallons/A spray volume. See label.
cymoxanil plus chlorothalonil (Ariston): 1.9 to 3.0 pt/A; PHI 3d, REI 12h, Groups 27 & M05. Spraying mature watermelons may result in sunburn of the upper surface of the fruit. See label.
difenoconazole plus benzovindiflupyr (Aprovia Top): 10.5 to 13.5 fl oz/A; PHI 0d, REI 12h, Groups 3 & 7.
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. Do not use for the control of 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. Labeled for alternaria and downy mildew only.
flutriafol (Rhyme fungicide): 5.0 to 7.0 fl oz/A; PHI 0d, REI 12h, Group 3. Labeled for black rot and anthracnose.
floxapyraxad plus pyraclostrobin (Merivon): 4.5 to 5.5 fl oz/A; PHI 0d, REI 12h, Groups 7 &11. Make no more than two sequential applications before alternating with a fungicide with a different mode of action.
mancozeb plus copper hydroxide (ManKocide): 2.0 to 3.0 lb/A; PHI 5d, REI 48h, Groups M03 & M01. Do not apply in a spray solution having a pH of less than 6.5 or tank mix with Aliette. Not for black rot.
penthiopyrad (Fontelis): 12.6 to 16.0 fl oz/A; PHI 1d, REI 12h, Group 7. Labeled only for black rot and alternaria. Should be used for control of black rot where group 7 fungicide resistance is suspected. Tank mix with a minimum of 1.5lb activew chlorothalonil/A.
polyoxin D zinc salt (OSO 5%SC): 6.5 to 13.0 fl oz/A; PHI 0d, REI 4h, Group 19.
pyraclostrobin (Cabrio EG): 12.0 to 16.0 oz/A; PHI 0d, REI 12h, Group 11. Do not make more than one application of Cabrio before alternating to a labeled fungicide with a different mode of action.
pyraclostrobin plus boscalid (Pristine): 12.5 to 18.5 oz/A; PHI 0d, REI 12h, Groups 11 & 7. Use caution in the addition of adjuvants or additives (see label).
Reynoutria sachalinensis extract (Regalia): 1.0 to 4.0 qt/A, foliar or ground application; PHI 0d, REI 4h, Group P05. Apply to ensure thorough coverage.
thiophanate-methyl (Topsin M WSB): 0.5 lb/A; PHI 1d, REI 24h, Group 1. Consecutive use of Topsin M may lead to buildup of resistant strains of fungi and loss of disease control. MAY be tank mixed with chlorothalonil or mancozeb. Labeled for GSB and anthracnose. See label for application methods.
zoxamide + chlorothalonil (Zing!): 36.0 fl oz/A; PHI 0d, REI 12h, Groups 22 & M05. Do not combine with anything other than water. See label for restrictions.

Downy Mildew (Pseudoperonospora cubensis)

Pseudoperonospora cubensis infects only members of the cucurbit family and is an obligate parasite; it only grows on living tissue and does not overwinter in the Northeast. Its survival depends on the presence of cucurbit hosts, either in climates that 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. Downy mildew first appears as watersoaked/yellow lesions on the upper side of the foliage that are often confined by leaf veins and angular in shape. 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/). 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 melon cultivars vary in their reactions. Spread of downy mildew within a field can be by air currents, rain splash, workers, and tools. 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. Maximize the distance from potential inoculum sources. Use plant spacings that reduce the density of the plant canopy and avoid overhead irrigation to minimize the length of leaf wetness periods. Squash and pumpkin cultivars are resistant to some pathotypes but are very susceptible to compatible pathotypes.

ametoctradin plus dimethomorph (Zampro): 14.0 fl oz/A; PHI 0d, REI 12h, Groups 45 & 40.
azoxystrobin (Quadris F): 11.0 to 15.5 fl oz/A; PHI 1d, REI 4h, Group 11. Do not alternate with other Group 11 fungicides. See label for application methods and mixing instructions.
Bacillus mycoides Isolate J (LifeGard WG^OG): 4.5 oz/100 gal water; PHI 0d, REI 4h, Group P06. Labeled for gourds and squash.
Bacillius subtilis strain QST 713 (Seranade ASO^OG): 2.0 to 4.0 qt/A; PHI 0d, REI 4h, Group BM02. See label for tank mixing precautions.
chlorothalonil (Bravo Weather Stik): 1.5 to 2.0 pt/A; PHI 0d, REI 12h, Group M05.
chlorothalonil plus oxathiapiprolin (Orondis Opti): 1.7 to 2.5 pt/A; PHI 0d, REI 12h, Groups M05 & 49. See label for application methods and restrictions.
copper hydroxide (Kocide 3000): 0.5 to1.25 lb/A; PHI 0d, REI 48h, Group M01. Discontinue use if crop injury occurs. Do not apply in a spray solution having a pH of less than 6.5 or tank mix with Aliette.
copper oxychloride plus copper hydroxide (Badge SC): 0.5 to 2.5 lb/A; PHI 0d, REI 48h, Group M01. Crop injury may occur from application at higher rates and shorter intervals. Tank mixes with foliar applied fertilizers during periods of excessive heat can result in crop injury. REI is 24hr for greenhouse use. See label.
cyazofamid (Ranman 400SC): 2.1 to 2.75 fl oz/A; PHI 0d, REI 12h, Group 21. Tank mix with an organosilicone surfactant or non-ionic surfactant. 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).
cymoxanil plus chlorothalonil (Ariston): 1.9 to 3.0 pt/A; PHI 3d, REI 12h, Groups 27 & M05. Spraying mature watermelons may result in sunburn of the upper surface of the fruit. See 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 two sequential applications of Forum before alternating to a fungicide with a different mode of action.
ethaboxam (Elumin): 8.0 fl oz/A; PHI 2d, REI 12h, Group 22, For downy mildew make foliar application. See label for restrictions
famoxadone plus cymoxanil (Tanos ): 8.0 oz/A; PHI 3d, REI 12h, Groups 11 & 27.Tank mix with an appropriate contact fungicide.
fenamidone (Reason 500 SC): 5.5 fl oz/A; PHI 14d, REI 12h, Group 11. Do not rotate with other Group 11 fungicides.
fosetyl Al (Aliette WDG): 2.0 to 5.0 lb/A; PHI 12d, REI 24h, Group P07. Do not tank mix with copper. See label for other restrictions.
mancozeb (Dithane F45): 1.6 to 2.4 qt/A; PHI 5d, REI 24h, Group M03. Do not tank mix with copper. See label for application methods and restrictions.
mancozeb plus copper hydroxide (ManKocide): 2.0 to 3.0 lb/A; PHI 5d, REI 48h, Groups M03 & M01. Do not apply in a spray solution having a pH of less than 6.5 or tank mix with Aliette.
oxathiapiprolin (Orondis Opti A): 2.0 to 4.8 fl oz/A; PHI 0d, REI 4, Group 49.
oxathiapiprolin plus mandipropamid (Orondis Ultra): 5.5 to 8.0 fl oz/A; PHI 0d, REI 4, Group 49 & 40.
phosphorous acid (Fosphite): 1.0 to 3.0 qt/100 gal; PHI 0d, REI 4h, Group P07. Do not apply to plants that are heat or moisture stressed. Copper phytotoxicity may occur; see label.
propamocarb HCl (Previcur Flex): 1.2 pt/A; PHI 2d, REI 12h, Group 28. Alternate with a contact fungicide (copper, chlorothalonil, sulfur).
pyraclostrobin (Cabrio EG): 8.0 to 12.0 oz/A; PHI 0d, REI 12h, Group 11. Do not make more than one application before alternating with a non-Group 11 fungicide.
pyraclostrobin plus boscalid (Pristine): 12.5 to 18.5 oz/A; PHI 0d, REI 12h, Groups 11 & 7. Use caution in the addition of adjuvants or additives (see label).
Reynoutria sachalinensis extract (Regalia): 1.0 to 4.0 qt/A; foliar or ground application; PHI 0d, REI 4h, Groups P05. Apply to ensure thorough coverage. Apply with another fungicide for downy mildew; see label.
trifloxystrobin (Flint): 4.0 fl oz/A; PHI 0d, REI 12h, Group 11. Do not rotate with another group 11 fungicide. Labeled for disease supression only. See label for restrictions.
zoxamide + chlorothalonil (Zing!): 36.0 fl oz/A; PHI 0d, REI 12h, Groups 22 & M05. Do not combine with anything other than water. See label for restrictions.
zoxamide plus mancozeb (Gavel75DF): 1.5 to 2.0 lb/A; PHI 5d, REI 48h, Groups 22 & M03. Do not tank mix Gavel with another M3 fungicide if the target pest is only downy mildew. Tank-mix only if a partner is required to control other diseases, such as copper for bacterial disease.

Phytophthora Blight and Fruit Rot

Vines can be infected any time during the growing season. Dark, water-soaked lesions develop on vines and can girdle the stem, resulting in rapid collapse and death of foliage above the lesion. Fruit rot can occur anytime in the season and typically begins as a water-soaked lesion becoming covered with white yeast-like mold. Fruit infection progresses rapidly, resulting in complete collapse of the fruit and total crop loss. 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, and all cucurbit species plus lima 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 from and improve drainage by sub-soiling after heavy rain events. Promptly disk under small areas where the disease appears along with a border of healthy appearing plants. Avoid working in wet fields and compacting the soil.

ametoctradin plus dimethomorph (Zampro): 14.0 fl oz/A; PHI 0d, REI 12h, Groups 45 & 40.
Bacillius subtilis strain QST 713 (Serenade ASO^OG): 2.0 to 4.0 qt/A; PHI 0d, REI 4h, Group BM02. See label for tank mixing precautions.
cyazofamid (Ranman 400SC): 2.75 fl oz/A; PHI 0d, REI 12h, Group 21. Mix with a surfactant for best results. Alternate sprays of Ranman with a fungicide with a different mode of action.
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.
ethaboxam (Elumin): 8.0 fl oz/A; PHI 2d, REI 12h, Group 22; Soil or foliar applications may be used. See label for restrictions
famoxadone plus cymoxanil (Tanos): 8.0 to 10.0 oz/A; PHI 3d, REI 12h, Groups 11 & 27. For SUPPRESSION of foliar and fruit phase ONLY. Tank mix with an appropriate contact fungicide with a different mode of action (copper or chlorothalonil).
fluopicolide (Presidio 4SC): 4 fl oz/A; PHI 2d, REI 12h, Group 43. Must be tank mixed with another fungicide with a different mode of action.
fosetyl-Al (Aliette WDG): 2.0 to 5.0 lb/A; PHI 12d, REI 24h, Group P07. Do not tank mix with copper compounds. Use the high rate when Phytophthora blight is active.
oxathiapiprolin (Orondis Opti A): 2.0 to 4.8 fl oz/A; PHI 0d, REI 4, Group 49. Apply as a soil or foliar application. Begin application at planting/transplanting for best results. See label.
oxathiapiprolin plus mandipropamid (Orondis Ultra): 5.5 to 8.0 fl oz/A; PHI 0d, REI 4, Group 49 & 40.
phosphorous acid (Fosphite): 1.0 to 3.0 qt/100 gal; PHI 0d, REI 4h, Group P07. Do not apply to plants that are heat or moisture stressed. Copper phytotoxicity may occur if applied in alteration with copper.
Reynoutria sachalinensis extract (Regalia): 1.0 to 4.0 qt/A; foliar or ground application; PHI 0d, REI 4h, Groups P05. Apply to ensure thorough coverage. Tank mix with another fungicide labeled for downy mildew control; see label.
zoxamide plus mancozeb (Gavel75DF): 1.5 to 2.0 lb/A; PHI 5d, REI 48h, Groups 22 & M03. Do not tank mix Gavel with another M3 fungicide if the target pest is only phytophthora blight. Tank-mix only if a partner is required to control other diseases, such as copper for bacterial disease.

Plectosporium Blight (Plectosporium tabacinum)

When Plectosporium blight occurs, rotate away from summer squash and pumpkins for 2 years. Choose sunny, well-drained sites for planting cucurbits. Scout for disease and apply fungicides when disease first occurs. Lesions of Plectosporium blight are most often observed on the stems of affected plants and can be small, irregularly shaped and often coalesce to form a scabby area. Fruit lesions can be confused with edema. Thorough coverage of foliage, vines, and fruit is necessary for good control. The Strobilurin (QoI) fungicides Flint (trifloxystrobin), Cabrio (pyraclostrobin), and Quadris (azoxystrobin) will control this disease but should not be rotated with each other or the pathogen will develop resistance. Apply a protectant fungicide such as chlorothalonil (Bravo) or mancozeb (Dithane) following a strobilurin.

azoxystrobin plus difenoconazole (Quadris Top): 12.0 to 14.0 fl oz/A; PHI 1d, REI 12h, Groups 11 & 3. Do not rotate with another group 11 fungicide.
difenoconazole plus benzovindiflupyr (Aprovia Top): 10.5 to 13.5 fl oz/A; PHI 0d, REI 12h, Groups 3 & 7.
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.
floxapyroxad plus pyraclostrobin (Merivon): 4.0 to 5.5 fl oz/A; PHI 0d, REI 12h, Groups 7 & 11. Make no more than two sequential applications before alternating with fungicides that have a different mode of action.
pyraclostrobin (Cabrio EG): 12.0 to 16.0 oz/A; PHI 0d, REI 12h, Group 11. Do not rotate with other Group 11 fungicides such as Quadris or Flint.
trifloxystrobin (Flint): 1.5 to 2.0 oz/A; PHI 0d, REI 12h, Group 11. Do not rotate with other Group 11 fungicides such as Quadris or Cabrio.

Post-Harvest Fruit Rot (Various Fungi)

Fruit and stem rot that develops after harvest is generally due to infection that took place in the field. Postharvest rot can be reduced by applying fungicides during the growing season on a regular basis, as for control of black rot. Control weeds to allow better air circulation. Wounds to the fruit that occur during harvest can also result in postharvest rot. For maximum storage life, refer to Postharvest Handling and Storage in the Cultural Practices section.

Powdery Mildew (Podosphaera xanthii)

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, the disease has a whjite powdery appearance and infects both the top and bottom of the leaf, making it 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). Resistances to Group 1 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 (Rally, Procure) is also widespread; use Rally or Procure 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) or on a preventative schedule for fields not scouted; do not begin using mobile fungicides when disease is widespread. A seven-day interval is recommended.

Bacillus amyloliquefaciens strain D747 (DoubleNickel 55^OG): 0.25 to 3.0 lb/A; PHI 0d, REI 4 h, Group BM02. Labeled for disease suppression only. For improved control; mix or rotate with a chemical fungicide.
Bacillus mycoides Isolate J (BmJ WG^OG, AKA LifeGard^OG): 4.5 oz/100 gal water; PHI 0d, REI 4h, Group P06. See label for application methods.
chlorothalonil (Bravo Weather Stik): 2 to 3 pt/A; PHI 0d, REI 12h, Group M05. (Severe eye irritant, observe WPS provisions.)
copper compound (Champ 2F): 1.33 pt/A; PHI 0d, REI 48h, Group M01. Label varies with manufacturer and formulation. REI for products ranges from 4 to 48 hr. Discontinue use if crop injury occurs.
copper hydroxide (Kocide 3000): 0.5 to 1.25 lb/A; PHI 0d, REI 48h, Group M01. Discontinue use if crop injury occurs. Do not apply in a spray solution having a pH of less than 6.5 or tank mix with Aliette.
cyflufenamid (Torino): 3.4 oz/A; PHI 0d, REI 4h, Group U06.
cyprodinil plus fludioxonil (Switch 6.25 WG): 11.0 to14.0 oz/A; PHI 1d, REI 12h, Groups 9 & 12. Good coverage is essential for good disease control. Use a minimum of 10 gallons/A spray volume. See label
cymoxanil plus chlorothalonil (Ariston): 3.0 pt/A; PHI 3d, REI 12h, Groups 27 & M05. Spraying mature watermelons may result in sunburn of the upper surface of the fruit. See label.
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.
flutriafol (Rhyme Fungicide): 5.0 to 7.0 fl oz/A; PHI 0d, REI 12h, Group 3. See label for surfactant recommendations and restrictions.
mancozeb plus copper hydroxide (ManKocide): 2.0 to 3.0 lb/A; PHI 5d, REI 48h, Groups M03 & M01. Do not apply in a spray solution having a pH of less than 6.5 or tank mix with Aliette.
metrafenone (Vivando): 15.4 fl oz/A; PHI 0d, REI 12h, Group 50. Must be applied before symptoms appear. Fro established infections, apply in a tank mix with a curative fungicide. Make no more than 3 applications per year. Rotate to a fungicide with a different Group # after 2 applications. Do not mix with horticultural oil.
monopotassium phosphate (Nutrol): 10.0 to 20.0 lb/A; PHI 0d, REI 4h, Group NC. Apply 2 to 4 sprays beginning at fruit set. Use a maximum of 3 lb product/10 gal spray solution. See label for application methods and restrictions.
myclobutanil (Rally 40WS): 2.5 to 5.0 oz/A; PHI 0d, REI 24h, Group 3. Observe a 30-day plant back interval. See label. (
neem botanical oil (Trilogy^OG): 0.5 to 1% solution/A; PHI 0d, REI 4h, Group NC. See label for application method. Thorough coverage is essential.
parrafinic (mineral oil) (JMS Stylet-Oil^OG): 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): 12.0 to 16.0 fl oz/A; PHI 1d, REI 12h, Group 7.
polyoxin D (OSO 5%SC): 6.5 to 13.0 fl oz/A; PHI 0d, REI 4h, Group 19.
potassium bicarbonate (Kaligreen^OG): 2.5 to 5.0 lb/A; PHI 1d, REI 4h, Group NC.
pyraclostrobin plus boscalid (Pristine): 12.5 to 18.5 oz/A; PHI 0d, REI 12h, Groups 11 & 7.
quinoxyfen (Quintec): 4.0 to 8.0 fl oz/A; PHI 3d, REI 12h, Group 13. Tank mix with a protectant fungicide. Alternate with a non-Group 13 fungicide. Not labeled for use on edible-peel cucurbits.
Reynoutria sachalinensis extract (Regalia): 1.0 to 4.0 qt/A; foliar or ground application; PHI 0d, REI 4h, Groups P05. Use preventatively, before any disease development. Apply to ensure thorough coverage. Recommended to mix with a mobile fungicide.
sulfur (Microthiol Disperss): 5.0 to 10.0 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 fl oz/A; PHI 0d, REI 12h, Group 3. Use at the highest rate to prevent resistance development.

Scab (Cladosporium cucumerinum)

Scab is a significant problem for summer and winter squash, pumpkin, melon, and watermelon. Foliar symptoms include gray to brown lesions with a yellow halo. Fruit lesions first appear as small pockmarks, resembling insect damage.

Resistant cultivars of cucumber are widely available. Where scab has been a problem, plant in sunny locations where cool air does not tend to accumulate. The pathogen survives in the soil on infected crop debris, may be seedborne, and is capable of saprophytic growth. Rotate with non-cucurbit crops for 2-3 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.

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.
chlorothalonil plus potassium phosphite (Catamaran): 6.0 pt/A; PHI 1d, REI 12, Groups M05 & P07. Do not apply under certain weather conditions (drought and conducive to sunburn); see label
difenoconazole plus benzovindiflupyr (Aprovia Top): 10.5 to 13.5 fl oz/A; PHI 0d, REI 12h, Groups 3 & 7.
mancozeb plus copper hydroxide (ManKocide): 2.0 to 3.0 lb/A; PHI 5d, REI 48h, Groups M03 & M01. Do not apply in a spray solution having a pH of less than 6.5 or tank mix with Aliette.
polyoxin D zinc salt (OSO 5%SC): 6.5 to 13.0 fl oz/A; PHI 0d, REI 4h, Group 19. Mix in sufficient water to ensure thorough coverage. See label for water volumes.

Angular leaf spot (Pseudomonas lachrymans)

Angular leaf spot is occasionally a serious disease in New England during wet seasons. Plow under crop residue after harvest. Rotate away from cucurbits for at least one year.

acibenzolar-s-methyl (Actigard 50WG): 0.5 to 1.0 oz/A; PHI 0d, REI 12h, Group P01; Apply to healthy, actively growing plants.
Bacillus subtilis strain QST713 (Serenade ASO^OG): 2.0 to 4.0 qt/A; PHI 0d, REI 4h, Group BM02. See label for mixing precautions.
copper hydroxide (Kocide 3000): 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. Discontinue use if crop injury occurs; see label.
copper octanoate (Cueva FL): 33 gal/A; PHI od, REI 4h, Group M01; May be used in greenhouse.
mancozeb plus copper hydroxide (ManKocide): 2.0 to 3.0 lb/A; PHI 5d, REI 48h, Groups M03 & M01. Do not apply in a spray solution having a pH of less than 6.5 or tank mix with Aliette.

Bacterial Wilt (Erwinia tracheiphila)

Because this bacterium is transmitted systemically by cucumber beetles, copper sprays are of no value. Cucumber beetles must be controlled by appropriate insecticide programs. Symptoms include rapid wilt of plants with no recovery overnight. Scout twice weekly at seedling stage for cucumber beetles. Treat when beetle numbers reach the threshold of 1 beetle per 100 feet of row. Use crop rotation to reduce beetle numbers. Rogue infected plants. Spunbonded row covers will exclude beetles. Plant a sprayed perimeter trap crop of Blue Hubbard squash to protect more susceptible crops. Dipping transplants in a kaolin solution will provide some protection as an antifeedant.

Cucurbit Viruses: CMV, WMV-II, PRSV-W and ZYMV

Refer to the discussion of these viruses in the section in Cucumber, Muskmelon and Watermelon.

Disease Control