Silver Maple Leaf Drop: Maple Petiole Borer, Not Disease

23–30-year-old silver maple near Chicago drops green leaves with brown/black veins near stem. Owner asks cause.

Diagnosis: Maple Petiole Borer

Tiny wasp larvae tunnel in leaf petioles, weakening them. Leaves fall with short petiole stubs (black, shriveled). 25–30% leaf drop typical.

Key Points

• One generation/year; larvae in soil until next spring.
• No health impact on tree.
• Insecticides not recommended (timing difficult, damage minor).
• Sanitation: collect and destroy fallen petiole stubs 7–10 days after first drop.

Raking leaves doesn't help—larvae aren't in blades.