Russeting of plum can be caused by several factors. Rain during the period of full bloom, mechanical rubbing against other fruit or branches caused by wind, or other injury of the (russet scab) fruit surface can result in russet symptoms. High winds following full bloom and copper fungicide applications are other causes of russeting on French prunes. Affected fruit initially show shiny areas on the surface where normal wax is lacking. The shiny area develops into a brown, corky or scabby area just before fruit harvest. Affected fruit may be misshapen. Thrips may cause similar russeting symptoms on all stone fruits.

Management Options

Non-Chemical Management

Avoid overhead watering during bloom and petal fall.

Select non-chemical management options as your first choice!

Chemical Management

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

Though no fungal or other microorganisms have been associated with russet scab, fungicides applied during the bloom period control the problem. A yeast has been associated with russet on pome fruit. Russeting caused by wind or thrips would not be managed with fungicide applications. 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
GardenTech Daconil Fungicide Conc
Active ingredient: chlorothalonil | EPA reg no: 67572-82-71004
Ortho Max Garden Disease Control Conc
Active ingredient: chlorothalonil | EPA reg no: 239-2522
This list may not include all products registered for this use.

Images

+ Show larger images


Caption: Fruit russeting on plum Photo by: R.S. Byther

WSU Extension

Hortsense