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Caption: Powdery mildew on cucumber
Photo by: R.S. Byther
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Cantaloupe, Melons : Powdery mildew
(revision date: 5/7/2015)
Biology
Powdery mildew is a common fungal disease of melons. Upper and lower leaf surfaces and stems are typically affected. Small white spots quickly enlarge into patches of characteristic powdery-white fungal growth. Older leaves, shaded leaves, and leaf undersides are the favored locations for powdery mildew development, but it can quickly spread to involve large portions of the plant. Tiny, speck-like, black fungal structures may be present in the white mats. Severely affected leaves may yellow and drop prematurely. Fruit quality can be affected and yield is reduced. Disease development is favored by humid weather, cool nights, and cloudy days. Dense plantings are more likely to be affected. The fungus can overwinter on diseased vines.
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Management Options
Non-Chemical Management
- Plant resistant varieties if available. Resistant cantaloupe varieties include 'All Star', 'Durango', 'Edisto', 'Edisto 47', 'Hy-Mark', 'Larado', 'Magnum 45', 'Market Star', 'Road Runner', 'Saticoy Hybrid', 'Sierra Gold', 'Super Market', 'Tasty Sweet', 'Top Mark', 'Top Score', and others.
- Rotate crops. Do not plant melons, squash, or related species in the same location for at least two years.
- Space plantings to provide good air circulation.
- Remove all plant debris from the garden. Destroy or discard (do not compost) diseased materials.
Select non-chemical management options as your first choice!
Chemical Management
Begin applications when conditions are favorable for disease. Repeat at weekly intervals if necessary.
Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions. - Bayer Advanced Natria Neem Oil Conc [Organic]
Active ingredient: clarified hydrophobic extract of neem oil | EPA reg no: 70051-2-72155 - Bi-Carb Old-Fashioned Fungicide [Organic]
Active ingredient: potassium bicarbonate | EPA reg no: 54705-10 - Monterey Horticultural Oil [Organic]
Active ingredient: mineral oil/pet distillate light | EPA reg no: 48813-1-54705 - Safer Brand Garden Defense Multi-Purpose Spray Conc [Organic]
Active ingredient: clarified hydrophobic extract of neem oil | EPA reg no: 70051-2-42697 - This list may not include all products registered for this use.
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Images
+ Show larger images
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Caption: Powdery mildew on cucumber
Photo by: R.S. Byther
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Caption: Powdery mildew on cucumber
Photo by: R.S. Byther
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Caption: Powdery mildew on squash
Photo by: R.S. Byther
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