WSU Extension


Blueberry : Botrytis blight
(revision date: 3/6/2015)

Botrytis is a fungus that survives on dead twigs of bushes and prunings. It also overwinters on dead organic matter or on the soil surface. During wet periods of the spring, the organism produces vast numbers of spores, which spread by wind and splashing water. Blossoms take on a brown, water-soaked appearance and die, later exhibiting dense grayish powdery masses of Botrytis spores. Infections can move through the blossoms rapidly and often destroy the whole floral structure. Also, the disease can move from blossoms back into fruit-producing wood. Young leaves may show pale brown lesions. Fruit may shrivel and be covered with the typical gray sporulating structures after harvest. Cultivars that tend to retain floral structures for longer periods are more susceptible.
Management Options

Non-Chemical Management
  • Avoid overhead watering and other practices which cause moist conditions in the canopy.
  • Clean up plant debris, including mummified fruit. Destroy or discard (do not compost) diseased materials.
  • Prevent injury to the fruit, which can facilitate disease development.
  • Space plantings and prune to provide good air circulation and reduce humidity.
  • Avoid late-season fertilization.
Select non-chemical management options as your first choice!

Chemical Management

Apply at beginning of fruit set after bloom is gone. Make 2 or 3 additional applications at 10- to 14- day intervals up to 3 weeks prior to harvest or when weather dries. Copper products offer only slight control.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bonide Liquid Copper Fungicide Conc/Organic Gardening
    Active ingredient: copper octanoate  |  EPA reg no: 67702-2-4
  • This list may not include all products registered for this use.
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Caption: Botrytis infection on blossom clusters
Photo by: R.S. Byther
Caption: Botrytis fruit rot
Photo by: R.S. Byther
Caption: Botrytis blight on new growth
Photo by: P.R. Bristow
Caption: Botrytis overwintering bodies
Photo by: P.R. Bristow
Caption: Botrytis infection on blossom clusters
Photo by: R.S. Byther
Caption: Botrytis leaf damage
Photo by: R.S. Byther