WSU Extension programs and employment are available to all without discrimination. Evidence of noncompliance may be reported through your local Extension office.
Willow: Twig blight (Venturia)
categories: Ornamental trees Ornamentals Willow Willow Diseases
revision date: 2022-11-29 12:00
Photo by: R.S. Byther
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
Use Integrated Pest Management (IPM) for successful plant problem management.
Non-chemical Management
Select non-chemical management options as your first choice!
- 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.
Chemical Management
IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.
- 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.
Approved Pesticides
Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
WSU Extension programs and employment are available to all without discrimination.
Evidence of noncompliance may be reported through your local Extension office.