Bigleaf Maple Aphid Identification and Management

Bright green, worm-like insects with three leg pairs and antennae on fallen maple leaves near fir trees likely indicate the bigleaf maple aphid (Drepanosiphum oregonensis), a Mediterranean native now established in North America.

Key Identification Features

• Feed on leaf undersides, producing sticky honeydew
• Overwinter as eggs on twigs near leaf buds
• Populations explode in spring, decline by fall
• Association with fir trees may be coincidental microclimate preference

Why Fall Treatment Is Ineffective

Leaf drop is imminent, and eggs for next year are already laid on woody tissue. Raking leaves won't significantly reduce next spring's population since eggs overwinter on the tree, not in leaf litter.

Recommended Action

• Contact Washington State Extension for positive ID (county offices here)
• Monitor next spring for early infestation signs
• If treatment needed, target crawler stage with horticultural oil or insecticidal soap
• Maintain tree health with proper watering—stressed trees attract more aphids

This introduced species rarely kills established maples but can cause premature leaf drop and honeydew nuisance.