WSU Extension

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Caption: Aphid damage on rhododendron
Photo by: A.L. Antonelli
  
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Rhododendron : Aphids
(revision date: 3/10/2017)


Biology
Aphids cause twisting, curling, or puckering of new growth by their feeding. Whitish cast skins and green live aphids may be visible on the undersides of leaves. Honeydew, a shiny, sticky substance excreted by aphids, may be present on the leaves, as may sooty mold, a black fungus which grows on the honeydew.
Management Options

Non-Chemical Management
  • Natural aphid predators such as ladybird beetles, lacewings, parasitic wasps, and syrphid or hover flies can maintain aphid populations at reasonable levels.
  • Aphids can be washed from foliage with a strong stream of water.
  • Maintain proper plant nutrition. Healthy plants are less susceptible to insect damage, and high nitrogen levels in the foliage encourages aphid reproduction.
Select non-chemical management options as your first choice!

Chemical Management


Thorough coverage of the foliage including lower leaf surfaces is important when using foliar sprays. Follow label instructions for products applied as a drench. Apply one of the following when aphids are noticed. 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
  • Safer Brand BioNEEM Multi-Purpose Insecticide & Repellent Conc [Organic]
    Active ingredient: azadirachtin  |  EPA reg no: 70051-6-42697
  • Safer Brand Garden Defense Multi-Purpose Spray Conc [Organic]
    Active ingredient: clarified hydrophobic extract of neem oil  |  EPA reg no: 70051-2-42697
  • 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 damage on rhododendron
Photo by: A.L. Antonelli
Caption: Aphid colony
Photo by: Unknown
Caption: Aphid cast skins
Photo by: R.S. Byther