Maple Petiole Borer: Natural and Self-Limiting

What It Is

Small wasp larvae bore into leaf stems (petioles) in May, causing 25–30% of leaves to drop early. Stems break at a darkened spot; larvae remain in the tree portion, later dropping to soil to pupate.

No Control Needed

• Tree health unaffected; one generation per year.
• Insecticides impractical—timing is difficult and damage is minor.
• Sanitation: pick up and destroy fallen stem pieces (without leaves) 7–10 days after first drop to reduce next year’s population.

Raking leaves does not help—larvae are not in the leaf blade.