Powdery mildew of cucurbits is caused by the fungi Erysiphe cichoracearum and Podosphaera fuliginea. The disease cycle is initiated by windblown conidia, which infect cucurbits over a range of humidity (50 to 95%) during moderate to warm (68 to 80ºF) temperatures. E.cichoracearum is more active at lower temperatures than P. fuliginea. The pathogen overwinters on wild cucurbit hosts, weeds, and dead vines.
Powdery white spots appear first on leaves, and eventually grow to cover entire leaves. Symptoms usually develop on the bottom surface of older leaves first, but all leaves become diseased as plants age. Infected leaves wither and die, leading to premature defoliation. Powdery mildew can reduce fruit yield and size, but the amount of damage is directly related to the amount of time plants have been diseased.
AQ10 biofungicide is a fungal hyperparasite (Ampelomyces quisqualis) of the powdery mildew fungus. AQ10 must be applied preventatively along with a mineral-oil or silicone surfactant early in the morning or later at night to be most effective. The use of conventional fungicides such as EBDCs, sulfur, and strobilurins should not be applied when AQ10 is used for powdery mildew control.
Eliminate weeds in and around cucurbit fields. Resistant cucumber and melon varieties are available and should be planted if suitable for your marketing and production needs. Several races of the powdery mildew fungi have been identified, and resistant varieties must be matched against the prominent races of the pathogens to be most effective.
Chemical controls must be used in combination with cultural controls to be most effective. Resistance to several fungicides has been reported in the powdery mildew fungi, so fungicides with different modes of action must be rotated or tank-mixed to prevent or delay resistance development. Thorough coverage is essential for effective disease control.
Product List for Powdery Mildew:
Pesticide |
Product per acre |
Application Frequency
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Remarks |
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Chlorothalonil and Chlorothalonil Mixtures |
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Bravo 720 |
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Do not graze or feed debris to livestock; 7 day PHI |
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Bravo Ultrex |
1.4-1.8 lb |
7-10 days |
Maximum of 16.5 pounds per season; 0 day PHI |
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Bravo WeatherStik |
1.5-2.0 pt |
7-10 days |
Maximum of 20 pints per season; 0 day PHI |
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Echo 720 |
1.5-2.0 pt |
7-10 days |
Maximum of 2.5 gallons per season; 7 day PHI |
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Echo 90DF |
1.2-1.6 lb |
7-10 days |
Maximum of 16.67 pounds per season; 7 day PHI |
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Echo Zn |
2.2 to 2.8 pt |
7-10 days |
Maximum of 3.6 gallons per season; 7 day PHI |
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Ridomil/Bravo |
1-2 lb |
7-14 days |
7 day PHI |
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Copper Fungicides |
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Champ Dry Prill |
1.33 lb |
5-7 days |
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Champ Formula 2 |
1.33 pt |
5-7 days |
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Copper-Count-N |
4-6 pt |
7 days |
Mid-harvest. |
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Cuprofix Disperss |
2.5 lb |
5-7 days |
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Kocide 101 |
1.5-3 lbs |
5-7 days |
May cause injury |
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Kocide DF |
1.5-3 lbs |
5-7 days |
May cause injury |
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Kocide 4.5LF |
1-2 pts |
5-7 days |
May cause injury |
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Kocide 3000 |
0.5-1.25 lb |
5-7 days |
May cause injury |
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Nordox |
1.5-2.0 lb |
7-10 days |
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Tri Basic Copper |
2-4 pt |
7-10 days |
1 day PHI |
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EBDC, Copper/EBDC, and EBDC/Zoxamide Mixtures |
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Cuprofix Disperss MZ |
4-7.25 lb |
3-10 days |
Maximum of 63.1 pounds per season; 5-14 day PHI |
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Dithane |
2-3 lb |
7-10 days |
Maximum of 25.6 pounds per season; 5 day PHI; use a non-ionic surfactant to improve performance |
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Gavel 75DF |
1.5-2.0 lb |
7-10 days |
Maximum 16 pounds per season; 5 day PHI; include a nonionic surfactant to improve performance |
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Maneb 75 DF |
1.5-2.0 lb |
7-10 days |
Maximum of 17.1 pounds per season; 5 day PHI |
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Manex 80W |
1.5-2.0 lb |
7-10 days |
Maximum of 16.0 pounds per season; 5 day PHI |
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Manex |
2.4-3.2 pt |
7-10 days |
Maximum of 25 pints per season; 5 day PHI |
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ManKocide |
2.0-2.5 lb |
7-10 days |
Maximum of 128 pounds per season; 5 day PHI |
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Penncozeb 80W |
1.5-3.0 lb |
7-10 days |
Maximum of 24.0 pounds per season; 5 day PHI |
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Penncozeb 75DF |
1.5-3.0 lb |
7-10 days |
Maximum of 25.6 pounds per season; 5 day PHI |
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Myclobutanil |
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Nova 40W,Rally 40W |
2.5-5 oz |
7-10 days |
Maximum of 1.5 lb/A per season; 0 PHI; 30 day plant back restriction |
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Strobilurins and Strobilurin Mixtures |
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Cabrio |
12-16 oz |
7-14 days |
Maximum of 4 applications or 64 oz per season; Alternate with different modes of action; 0 day PHI |
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Flint |
4 oz |
7-14 days |
Suppression only; Maximum of 4 applications or 16 ounces per seaon; 0 day PHI; rotate with fungicides with different modes of action |
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Quadris |
11.0-15.4 fl oz |
5-14 days |
Maximum of 4 applications or 2.88 quarts per season; Alternate with different modes of action; 1 day PHI |
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Tanos |
8 oz |
5-7 days |
Rotate with fungicides with a different mode of action, such as chlorothalonil or mancozeb; Maximum of 48 ounces per season; 3 day PHI |
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Thiophanate Methyl |
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Topsin M 70WP |
0.5 lb |
7-14 days |
Maximum of 3 lb per season; Alternate fungicide sprays or tank-mix with fungicides with a different mode of action; 1 day PHI |
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Topsin 4.5 FL |
10 fl oz |
7 days |
Maximum of 60 fl oz per season; Alternate fungicide sprays or tank-mix with fungicides with a different mode of action; 1 day PHI |
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Topsin WSB |
0.5 lb |
7-14 days |
Maximum of 3 lb per season; Alternate fungicide sprays or tank-mix with fungicides with a different mode of action; 1 day PHI |
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Triazole |
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Nova |
2.5-5.0 oz |
7-10 days |
Maximum of 1.5 pounds; 0 day PHI |
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Procure |
4-8 oz |
7-14 days |
Maximum of 40 ounces per season; Alternate with fungicides with different modes of action; 0 day PHI |
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The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality. |
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Categories: Cucurbits, Disease, Powdery Mildew, Cucumber, Melon, Pumpkin, Squash, Zucchini
Date: 04/01/2007