WSU Extension

Hortsense

Spruce : Spruce aphid
(revision date: 2/14/2019)


Biology
Plants affected by spruce aphid first show yellowish blotches on the needles, sometimes with honeydew (sticky material excreted by the aphids) present. The needles may turn completely yellow or brown and drop. Spruce aphids feed during the winter and early spring, before new growth occurs, so affected trees may have needles only on the tips of branches later in the year. Damage is usually not apparent until after aphids have left the tree. Check weekly for aphids on important trees starting about November (monitor less important trees beginning around February, depending on weather).
Management Options

Non-Chemical Management
  • Plant resistant species whenever possible. American spruces are more susceptible to damage than Asian or Eurasian species.
  • Regular hosing of small trees with a strong stream of water will help wash off aphids.
  • Natural predators such as spiders and ladybird beetles may help control populations. Cold winter weather can also reduce aphid numbers.
  • Ants will protect and 'farm' aphids for their honeydew, so they should be controlled.
Select non-chemical management options as your first choice!

Chemical Management

If you use a foliar spray, thorough coverage of the foliage is important, including all needle surfaces. Apply insecticides in fall or winter (unless temperatures are extremely low). Oil products should not be used if there is any danger of freezing. Horticultural oils, soap-based products and some other products may cause discoloration of spruce needles, particularly on Colorado blue spruce. Read labels carefully and test on a small area before application. DO NOT APPLY Safer Brand Insect Killing Soap Concentrate II to Colorado blue spruce. 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.
  • All Seasons Horticultural & Dormant Spray Oil Conc [Organic]
    Active ingredient: oil/pet distillate  |  EPA reg no: 4-80
  • Bonide Systemic Insect Control
    Active ingredient: acephate  |  EPA reg no: 239-2461-4
  • 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: Spruce aphid damage
Photo by: R.S. Byther
Caption: Spruce aphid needle loss
Photo by: A.L. Antonelli
Caption: Aphid damage and sooty mold buildup
Photo by: A.L. Antonelli
Caption: Spruce aphid damage
Photo by: C.R. Foss