Giant willow aphid
10 host plants
Last updated
Large, black or dark grey aphids (up to 0.3 inch) appear on willow stems and branches in clusters during late spring and summer throughout Western Washington lowlands. Affected plants secrete copious honeydew that coats leaves, branches, and underlying structures; this sticky residue attracts ants and supports sooty mold growth. The aphids congregate openly on stems rather than hiding in curled leaves. Willow species are particularly susceptible.
Maintain willow trees in vigorous growth with appropriate watering during dry periods. Monitor for colonies and encourage natural predation by avoiding insecticides. A strong water spray can dislodge colonies. For landscape willows where honeydew is problematic, apply neem oil or insecticidal soap, repeating every 7 to 10 days. Horticultural oil in late fall targets overwintering populations.
Quick Reference
Cultural Controls
- biological control Many parasites and predators attack aphid.
- Monitor the proportion of aphid mummies to unparasitized adults and the number of predators such as lady beetles.
- If the biocontrol agents appear to be gaining control, avoid sprays which would disrupt this system.
- Most products available for aphid control are highly disruptive of natural enemies.
- Management-cultural control Aphid populations tend to be higher in plants that are fertilized liberally with nitrogen.
- Prune out suckers...