Giant Willow Aphids: Identification and Control

Identifying the Problem

Those clusters of small black insects with orange legs covering your pussy willow tree are Giant Willow Aphids (Tuberolachnus salignus)—one of the largest aphid species, reaching up to ¼ inch long. Their presence explains the sticky residue (honeydew) on leaves, branches, and surrounding furniture, as well as the bees and wasps attracted to the sugary secretion.

Why They're a Nuisance

Giant Willow Aphids feed exclusively on willows, sucking plant juices from leaves and twigs. They excrete honeydew, a sticky, sugar-rich substance that coats surfaces and promotes black sooty mold growth. The honeydew also draws stinging insects, creating an unpleasant environment around the tree.

Effective Control Strategies

For Smaller Trees (Reachable Foliage)

Spray thoroughly with Orthene (acephate), a systemic insecticide absorbed by foliage. Cover all leaf surfaces, including undersides.

For Large Trees (Difficult to Spray)

Apply Bayer Advanced 12-Month Tree & Shrub Insect Control (imidacloprid) as a soil drench around the base. Roots absorb the systemic insecticide and translocate it to leaves and twigs, killing aphids as they feed. This treatment lasts the entire season but takes 2–3 weeks to reach the canopy, especially in dry conditions.

Combined Approach (Best for Large Trees)

Spray reachable foliage with Orthene using a pump sprayer, and apply the Bayer soil drench for full canopy coverage. This dual method provides immediate knockdown and season-long protection.

Product reference: Bayer Advanced Tree & Shrub Insect Control