Poplar: Marssonina leaf spot
Photo by: R.S. Byther
Biology
Marssonina leaf spot is a fungal disease which is favored by wet weather. Leaves develop spots or flecks which are initially bronze or brown with yellow edges.
These spots enlarge and may involve almost the entire leaf. Later, the spots turn black and may have gray fungal fruiting bodies on the surface.
Severe infections may result in premature leaf drop, which can reduce growth. Twigs may also be infected.
The fungus overwinters in infected leaves on the ground. Trembling or quaking aspen (Populus tremuloides), Eastern cottonwood (P. deltoides), black cottonwood (P. trichocarpa), and balsam poplar (P. balsamifera) are typically infected.
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!
- Space plantings and prune to improve air circulation.
- Prune and destroy infected twigs. Disinfect pruning tools after use.
- Rake and destroy (do not compost) infected leaves.
Chemical Management
IMPORTANT: Always read and follow label directions when working with pesticides.
For more information on using pesticides visit :
- Apply fungicides at budbreak to protect new growth.
- 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.