Northwest berry Foundation

Management Detail

Powdery Mildew

in Blackberries

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Latin name: Sphaerotheca macularis


Blackberries and raspberries are usually not affected by this fungal disease but 'Boysenberry' is very susceptible. Warm, dry weather favors development of this disease. In spring, ascospores are the primary inoculum. Severe mildew retards, dwarfs, and distorts plant parts and makes fruit unsalable.



  • Favored by dry, moderate weather conditions.
  • Infected leaves develop light green (chlorotic) spots on the upper surface, often with white mycelial growth on the lower leaf surface.
  • Spots may appear water-soaked, and leaves have a mottled appearance similar to that caused by mosaic virus infection.
  • Infected shoot tips and fruit may also become covered with white, mycelial growth.
  • Severely infected shoots become long and spindly with dwarf leaves that curl upward.
  • Severely diseased plants may be stunted.

Cultural Controls:

  • Do not plant close to wooded areas that might shade the field.
  • Remove wild blackberries from around the field.
  • Planting resistant cultivars may be an option in some situations.
  • Remove any infected, late-forming suckers.


For information about chemical controls, check with our Pesticide Guide.


photo from Oregon State University


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