Plum, Prune (Fresh): Brown rot

Biology

Brown rot is a blossom-infecting fungal disease. Infected flowers first appear water-soaked, then wilt and die. The light brown blossoms remain attached to the twigs, becoming covered with a grayish-brown fungal growth during wet weather. Blossom or fruit infections may spread to spurs. Infected twigs develop sunken, elongate cankers with gumming at the margins. Leaves on girdled shoots turn brown and remain attached. Infected fruit initially show a small brown spot which rapidly enlarges. The fruit remains fairly firm and often becomes covered with gray-brown fungus. The rot may also occur in stored fruit. Fruit may dry and harden into mummies, which serve as a source of infection in the spring, either on the tree or on the ground.

Management Options

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

Non-chemical Management

Select non-chemical management options as your first choice!

• Rake and destroy infected leaves and mummified fruit to reduce spread of disease. Remove mummified fruit remaining on the tree, as well.
• Prune out infected twigs in late spring or summer. Do not wait until the dormant season, when infected twigs are difficult to distinguish.
• Space plantings and prune to provide good air circulation. This will reduce the moist conditions favoring disease.
• Avoid overhead watering.
• Control insects that cause wounds and provide infection sites for the fungus.
• Avoid wounding fruit during harvest.

Chemical Management

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

• Apply fungicides just before blossoms open, at full bloom, and when most or all of the blossom petals have fallen.
• Control may also be obtained with sulfur. Bonide Infuse Systemic Disease Control should not be applied to Stanley type plums.
• Homeowners should not make foliar applications to trees over 10 ft tall.
• Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

Approved Pesticides

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

• Bonide Fung-onil Multi-Purpose Fungicide Concentrate
  Active ingredient: chlorothalonil [EPA registration number: 60063-9-4]
• Bonide Infuse Systemic Disease Control
  Active ingredient: propiconazole [EPA registration number: 100-773-4]
• Bonide Sulfur Plant Fungicide Micronized Spray or Dust RTU [Organic]
  Active ingredient: sulfur [EPA registration number: 4-62]
• GardenTech Daconil Fungicide Concentrate
  Active ingredient: chlorothalonil [EPA registration number: 67572-82-71004]
• Lilly Miller Sulfur Dust Fungicide/Insecticide Dust or Spray
  Active ingredient: sulfur [EPA registration number: 802-16]
• Hi-Yield Snake Eyes Dusting Wettable Sulfur
  Active ingredient: sulfur [EPA registration number: 7401-188-34911]
• Ortho Max Garden Disease Control Concentrate
  Active ingredient: chlorothalonil [EPA registration number: 239-2522]
• Spectracide IMMUNOX Multi-Purpose Fungicide Spray Concentrate
  Active ingredient: myclobutanil [EPA registration number: 9688-123-8845]
• This list may not include all products registered for this use.

Additional Image