WSU Extension

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Caption: Aphid colony
Photo by: Unknown
  
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Ornamental Plum : Hop aphid
(revision date: 2/14/2019)


Biology
Hop aphids are yellowish to bluish-green in color. They feed on plum, prune, cherry, and other hosts in the winter, then migrate to a summer host such as hops or sunflower. Some aphids remain on the winter host all year round. Their feeding causes leaves to roll. Typically, they are found on the underside of plum leaves, or inside the rolled leaves. Heavily infested plants may drop leaves, resulting in severe defoliation.
Management Options

Non-Chemical Management
  • Wash aphids from plants with a strong stream of water (most effective before leaves are rolled).
  • Remove aphids by hand and hand-pick rolled leaves (when practical) to control small infestations.
  • Natural predators and parasites, including ladybird beetles, lacewings, and parasitic wasps, help control aphid populations.
  • Control honeydew-feeding ants, which may protect aphid colonies.
  • Provide proper nutrition. High levels of nitrogen in the foliage encourages aphid reproduction. Switch to a slow-release or low-nitrogen fertilizer.
Select non-chemical management options as your first choice!

Chemical Management


Thorough coverage of the foliage is important, including lower leaf surfaces (follow label instructions for products applied as a drench). Apply oils in early spring before bud swell. 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.
  • Hi-Yield Dormant Spray
    Active ingredient: oil/pet distillate  |  EPA reg no: 7401-428
  • 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.
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Caption: Aphid colony
Photo by: Unknown