WSU Extension

Hortsense

Willow
 
Disease
Bacterial twig blight 
Marssonina leaf & twig spot 
Rust 
Twig blight (Venturia) 
Insect
Carpenterworm 
Poplar-and-willow borer 
Satin moth 
Spiny elm caterpillar 



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Caption: Willow twig blight cankers and dieback
Photo by: R.S. Byther
  
Willow : Twig blight (Venturia)
(revision date: 4/28/2014)


Biology
Also known as scab, willow twig blight infects leaves and twigs. The fungus first infects new foliage in the spring, causing brown to dark spots along the midrib of the leaves. The young leaves become scorched in appearance, wither, and drop, resulting in minor to severe defoliation (particularly near branch tips). The infection then grows into the twigs, where symptoms include small brown to black cankers which result in girdling and dieback of twigs and branches. Infected leaves and twigs may display a velvety, olive-brown fungal growth, especially along the leaf midveins. Older leaves and twigs are less susceptible to infection. The disease is apparently spread by splashing water and is favored by wet weather.
Management Options


Non-Chemical Management
  • Avoid overhead watering.
  • Space plantings and prune trees to improve air circulation.
  • Rake and destroy fallen leaves before the spring infection period.
  • Prune and destroy diseased twigs and branches in fall when practical.
  • Plant less-susceptible willows such as bay-leaved, osier, purple, and weeping.
Select non-chemical management options as your first choice!

Chemical Management

In spring, apply two or three times beginning when new leaves first appear and repeating at 10-14 day intervals, particularly in wet weather (14-day intervals for Spectracide IMMUNOX). 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.
  • 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: Willow twig blight cankers and dieback
Photo by: R.S. Byther