Birch Leafminer—Fenusa pusilla
Birch is host to a number of leaf-mining sawflies. Two of the more common miners are Messa nana (Klug) and Fenusa pusilla (Lepeletier). The name "leafminer" is derived from the larval habit of feeding, or mining, the plant tissues between the upper and lower surfaces of birch leaves.
The adult sawfly is a small, 1/4 inch long, black, fly-like wasp.
The small, white and slightly flattened larvae of the birch leafminer live within the birch leaves. They can be easily seen when the leaves are held up to the light.
Damage to the leaves of the host plant initially consists of small individual leaf mines; however, as these overlap forming larger blotches, wilting and gradual leaf death occurs.
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Identification and Control Information
- Birch Leafminers—Maine Forest Service
- Entomological Notes: Birch Leafminer (PDF)—Penn State College of Agricultural Sciences Cooperative Extension
- Fact Sheet: Birch Leafminer (PDF)—University of Rhode Island
- Toronto Master Gardener Factsheets: Birch Leafminer (PDF)—Toronto Botanical Garden
More Information
- Maine Forest Service: Conditions Reports (updated regularly) including annual summary reports
- Birch Leafminer, Fenusa pusilla—Center for Northern Woodlands Education
- How to Grow and Maintain a Healthy Birch Tree—USDA Forest Service
[Photos, left to right: Cheryl Moorehead, individual, Bugwood.org; Joseph O'Brien, USDA Forest Service, Bugwood.org; Whitney Cranshaw, Colorado State University, Bugwood.org]