Powdery mildew, caused by the fungus Sphaerotheca macularis, affects raspberries, especially on the primocanes, causing leaves to curl. The undersides of leaves are covered with a while fungus. In severe cases, the fungus appears on the upper leaf surface.
Red, black, and purple raspberries are susceptible to powdery mildew; varieties differ in susceptibility. Blackberries and their hybrids are usually not susceptible.
Flower buds, flowers, and fruit may also be infected by powdery mildew.
More information:
- Pest Management Detail – Powdery Mildew Berries Northwest
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