Raspberry: Powdery mildew
categories: Raspberry Raspberry Diseases Small Fruits
last review date: 2025-11-12 07:46
Photo by: R.S. Byther
Biology
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
See "Using Integrated Pest Management (IPM) in the Landscape" for successful problem management techniques.
Non-chemical Management
Select non-chemical management options as your first choice!
- 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.
Chemical Management
IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.
- 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.
Approved Pesticides
Examples of pesticides that are legal for home use in Washington State are listed below.
The list may not include all products registered for this use.
WSU Extension programs and employment are available to all without discrimination.
Evidence of noncompliance may be reported through your local Extension office.