WSU Extension


True Fir
Annosus root rot 
Armillaria root rot 
Current-season needle necrosis 
Grovesiella canker 
Interior needle blight 
Needle casts 
Phytophthora root rot 
Rust (Pucciniastrum) 
Rust (Uredinopsis) 
Balsam twig aphid 
Balsam woolly adelgid 
Giant conifer aphids 
Spruce budworm 
Spruce spider mite 

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Caption: Giant conifer aphids
Photo by: A.L. Antonelli
True Fir : Giant conifer aphids
(revision date: 3/22/2021)

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

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.
  • 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 salts of fatty acid  |  EPA reg no: 42697-60
  • This list may not include all products registered for this use.

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