Rhododendron: Aphids

• Categories: Ornamentals Rhododendron Rhododendron Insects Shrubs
• Last review date: 2025-06-27 09:54

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

See "Using Integrated Pest Management (IPM) in the Landscape" for successful problem management techniques.

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

• 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

If you choose to use a pesticide, some examples of products that are legal in Washington are listed below. Some products are labeled for just INDOOR or just OUTDOOR use, or may allow both uses. Be sure to choose a product appropriate for your situation. 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.