Brownheaded Ash Sawfly vs. Lady Beetle Larvae on Green Ash

Primary Pest: Brownheaded Ash Sawfly

Curled, sticky leaves with white fluffy material match sawfly feeding. Larvae are pale green "worms" that skeletonize leaves in May–June. One generation per year.

Secondary Insect: Lady Beetle Larvae

The spiky, dark larvae seen on leaves are beneficial predators eating sawfly larvae or aphids. They do not damage the tree.

Control Threshold

Treat only if >25% defoliation is imminent. Options:

• Bacillus thuringiensis (Bt) — ineffective on sawflies (they are not caterpillars).
• Carbaryl (Sevin), permethrin, or malathion — contact sprays applied when larvae are small.
• Soil-applied imidacloprid — systemic control for next season.

Cultural Note

Healthy, unstressed ashes tolerate complete defoliation once. Repeated years of heavy feeding warrant treatment.