Powdery mildew is a fungal disease which attacks the leaves, pods, and stems. Leaves and stems develop discolored spots. The spots later show characteristic white mats of powdery fungal growth which give a bluish cast to the foliage. Small black fruiting bodies of the fungus may be present in the white mats. The infected areas may die on some pea varieties, and some varieties including 'Oregon Sugar Pod' may show brown or black necrotic spots on affected pods. Infection early in the season may result in stunted plants. Powdery mildew may result in reduced yields. Warm days, cool nights, and humid weather favor development of powdery mildew, which is often worse in the fall. The fungus may be carried by infected seed, which is often gray-brown in color. It can also overwinter on infected plant debris.

Management Options

Non-Chemical Management

Plant peas early. Spring crops seldom show serious damage. Do not replant fall peas in the same location.
Plant resistant varieties such as 'Almoto', 'Aspen', 'Concord', 'Freezer 604', 'Knight', 'Sentry', 'Sounder', 'Super Sugar Melt' (snap pea), and others.
Clean up plant debris in the garden. Destroy or discard (do not compost) diseased materials.

Select non-chemical management options as your first choice!

Chemical Management

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

Apply according to label instructions. Do not apply sulfur products if temperatures are high or leaves may burn.

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 reg no: 54705-10
Hi-Yield Snake Eyes Dusting Wettable Sulfur
Active ingredient: sulfur | EPA reg no: 7401-188-34911
Lilly Miller Sulfur Dust Fungicide/Insecticide Dust or Spray
Active ingredient: sulfur | EPA reg no: 802-16
Safer Brand Garden Fungicide/Flowers, Fruit & Vegetables Conc
Active ingredient: sulfur | EPA reg no: 42697-37
This list may not include all products registered for this use.

Images

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Caption: Powdery mildew on pea Photo by: R.S. Byther
Caption: Powdery mildew on pea Photo by: R.S. Byther

WSU Extension

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