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Rhododendron: Aphids

categories: Ornamentals Rhododendron Rhododendron Insects Shrubs

revision date: 2023-04-04 12:00

Aphid damage on rhododendron.
Aphid damage on rhododendron
Photo by: A.L. Antonelli

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

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

  • 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.

Chemical Management

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

  • 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.

Approved Pesticides

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

  • Safer Brand BioNEEM Multi-Purpose Insecticide and Repellent Concentrate [Organic]
    Active ingredient: azadirachtin [EPA registration number: 70051-6-42697]
  • Safer Brand Garden Defense Multi-Purpose Spray Concentrate [Organic]
    Active ingredient: clarified hydrophobic extract of neem oil [EPA registration number: 70051-2-42697]
  • Safer Brand Insect Killing Soap Concentrate II [Organic]
    Active ingredient: potassium salts of fatty acid [EPA registration number: 42697-60]
  • This list may not include all products registered for this use.

Additional Images