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

Non-Chemical Management

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.

Select non-chemical management options as your first choice!

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.

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

Bonide Fung-onil Multi-Purpose Fungicide Conc
Active ingredient: chlorothalonil | EPA reg no: 60063-9-4
Bonide Infuse Systemic Disease Control
Active ingredient: propiconazole | EPA reg no: 100-773-4
Bonide Sulfur Plant Fungicide Micronized Spray or Dust RTU [Organic]
Active ingredient: sulfur | EPA reg no: 4-62
GardenTech Daconil Fungicide Conc
Active ingredient: chlorothalonil | EPA reg no: 67572-82-71004
Hi-Yield Snake Eyes Dusting Wettable Sulfur
Active ingredient: sulfur | EPA reg no: 7401-188-34911
Lilly Miller Sulfur Dust Fungicide/Insecticide Dust or Spray
Active ingredient: sulfur | EPA reg no: 802-16
Ortho Max Garden Disease Control Conc
Active ingredient: chlorothalonil | EPA reg no: 239-2522
Spectracide IMMUNOX Multi-Purpose Fungicide Spray Conc
Active ingredient: myclobutanil | EPA reg no: 9688-123-8845
This list may not include all products registered for this use.

Images

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Caption: Brown rot mummified plum Photo by: R.S. Byther
Caption: Brown rot blossom infection Photo by: R.S. Byther

WSU Extension

Hortsense