WSU Extension


Caption: Powdery mildew on raspberry
Photo by: R.S. Byther
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Raspberry : Powdery mildew
(revision date: 2/26/2016)

Powdery mildew is a fungal disease which can affect leaves, shoot tips, new canes, and fruit of red and black raspberries, blackberries, and hybrids including 'Logan' berries. Leaves show pale green to watersoaked spots on the upper surface, with corresponding patches of white, powdery fungal growth on the lower surface. Infected young leaves do not expand properly, curling upward at the margins and becoming stunted and deformed. Shoot tips may be entirely covered with fungal growth. Severe infections cause the shoots to become spindly and weak, and may stunt the whole plant. Fruit may become covered with the fungus, fail to reach full size, and die. Small, black fungal structures may be present in the white mats on leaves and stems later in the season. Powdery mildew development is favored by warm, cloudy, humid weather. The fungus overwinters in infected buds.
Management Options

Non-Chemical Management
  • Plant resistant varieties. The red raspberries 'Chilcotin', 'Meeker', 'Nootka', 'Sumner', and 'Willamette' are reported to be resistant to powdery mildew.
  • Space plantings, prune, and train to provide good air circulation and reduce humidity.
  • Carefully cut out and destroy or discard (do not compost) diseased suckers in the spring.
Select non-chemical management options as your first choice!

Chemical Management

Sulfur sprays may burn foliage in warm weather. Apply first spray of sulfur or potassium bicarbonate when first blooms open, then weekly until all fruit is set.

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
  • ferti-lome Horticultural Oil Spray RTSpray
    Active ingredient: oil/pet distillate  |  EPA reg no: 48813-1-7401
  • Lilly Miller Sulfur Dust Fungicide/Insecticide Dust or Spray
    Active ingredient: sulfur  |  EPA reg no: 802-16
  • Monterey Horticultural Oil [Organic]
    Active ingredient: mineral oil/pet distillate light  |  EPA reg no: 48813-1-54705
  • This list may not include all products registered for this use.
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Caption: Powdery mildew on raspberry
Photo by: R.S. Byther