WSU Extension

Hortsense

Cotoneaster
 
Disease
Bacterial blight 
Fire blight 
Scab 
Insect
Cotoneaster webworm 
Spider mites 



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Caption: Apple scab on leaves and young fruit
Photo by: R.S. Byther
  
Cotoneaster : Scab
(revision date: 1/22/2016)


Biology
Symptoms of scab on cotoneaster are similar to those on apple. A fungal disease, scab causes leaves and fruit to develop dark or black blotchy spots. Initially, the leaves show pale pinhead spots, which later darken to a velvety olive then black. The diseased leaves are often curled, puckered, or otherwise distorted. Affected leaves may turn yellow prematurely. Moist conditions favor disease development.
Management Options


Non-Chemical Management
  • Rake and destroy fallen leaves and fruit to reduce reinfection chances.
  • Avoid overhead irrigation or limit it to times when the foliage can dry quickly.
  • Prune and space plantings to reduce humidity and improve air circulation.
Select non-chemical management options as your first choice!

Chemical Management

Make a delayed dormant application. Repeat applications when foliage appears. 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 Infuse Systemic Disease Control Lawn & Landscape
    Active ingredient: thiophanate methyl  |  EPA reg no: 53883-183-4
  • Safer Brand Garden Fungicide/Flowers, Fruit & Vegetables Conc
    Active ingredient: sulfur  |  EPA reg no: 42697-37
  • This list may not include all products registered for this use.
Images

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Caption: Apple scab on leaves and young fruit
Photo by: R.S. Byther
Caption: Apple scab on leaf
Photo by: R.S. Byther
Caption: Apple scab
Photo by: R.S. Byther