Giant conifer aphids are large (up to 1/5") and dark brown to black in color. They overwinter as eggs on twigs or branches. Adults and nymphs begin feeding on stems in the spring. They excrete large amounts of honeydew (a sweet, sticky material), which may become covered with sooty mold, a black fungus.

Management Options

Non-Chemical Management

Provide proper plant culture. Healthy plants can tolerate more insect damage.
Avoid overfertilization. High levels of nitrogen in the foliage encourages aphid reproduction. Switch to a slow-release or low-nitrogen formula if necessary.
Hose infested trees with a strong stream of water to wash off insects.
Where practical, prune and destroy individual, heavily-infested branches.
Encourage natural aphid predators, including ladybird beetles and green lacewings.

Select non-chemical management options as your first choice!

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides

Thorough coverage of the foliage is important, including all needle surfaces. Apply one of the following in the spring. Homeowners should not make foliar applications to trees over 10 ft tall. Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.

Bonide Systemic Insect Control
Active ingredient: acephate | EPA reg no: 239-2461-4
Ortho Max Malathion Insect Spray Conc
Active ingredient: malathion | EPA reg no: 239-739
R-T-U Year-Round Spray Oil
Active ingredient: oil/pet distillate | EPA reg no: 6218-78
Safer Brand BioNEEM Multi-Purpose Insecticide & Repellent Conc [Organic]
Active ingredient: azadirachtin | EPA reg no: 70051-6-42697
Safer Brand Insect Killing Soap Conc II [Organic]
Active ingredient: potassium laurate | EPA reg no: 42697-60
This list may not include all products registered for this use.

Images

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Caption: Giant conifer aphids Photo by: A.L. Antonelli
Caption: Giant conifer aphids Photo by: A.L. Antonelli

WSU Extension

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