Blueberry: Botrytis blight

Biology

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

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

• 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.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

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

Approved Pesticides

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.

• Bonide Liquid Copper Fungicide Concentrate/Organic Gardening
  Active ingredient: copper octanoate [EPA registration number: 67702-2-4]
• This list may not include all products registered for this use.

Additional Images