Willow: Rust
Photo by: R.S. Byther
Biology
Willow rusts are fungal diseases that begin in early summer but are most noticed in late summer to early fall. Leaves first display yellow spots, which turn dark brown or black by late summer or early fall.
Severe infections cause leaves to drop, sometimes resulting in considerable defoliation. The fungus overwinters on dead leaves and infected twigs or on alternate hosts.
Alternate hosts for willow rusts include fir, larch, and Ribes species such as currants and gooseberries, depending on the rust species.
Rust infections on willows are not typically a serious problem, although growth of young trees may be somewhat slowed by defoliation.
Management Options
See "Using Integrated Pest Management (IPM) in the Landscape" for successful problem management techniques.
Non-chemical Management
Select non-chemical management options as your first choice!
- Rake and destroy all fallen leaves beneath willow trees.
- Avoid overhead watering and splashing water, which contribute to the spread of the disease.
Chemical Management
IMPORTANT: Always read and follow label directions when working with pesticides.
For more information on using pesticides visit :
- Apply when conditions favor disease.
- 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
If you choose to use a pesticide, some examples of products that are legal in Washington are listed below. Some products are labeled for just INDOOR or just OUTDOOR use, or may allow both uses. Be sure to choose a product appropriate for your situation. Always read and follow all label directions.
Additional Image
Photo by: R.S. Byther
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Evidence of noncompliance may be reported through your local Extension office.