Cantaloupe, Melons: Powdery mildew

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.

Management Options

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

• 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.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

• Begin applications when conditions are favorable for disease.
• Repeat at weekly intervals if necessary.

Approved Pesticides

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.

• Bi-Carb Old-Fashioned Fungicide [Organic]
  Active ingredient: potassium bicarbonate [EPA registration number: 54705-10]
• Monterey Horticultural Oil [Organic]
  Active ingredient: mineral oil/pet distillate light [EPA registration number: 48813-1-54705]
• Safer Brand Garden Defense Multi-Purpose Spray Concentrate [Organic]
  Active ingredient: clarified hydrophobic extract of neem oil [EPA registration number: 70051-2-42697]
• This list may not include all products registered for this use.

Additional Images