Rhododendron: Rhododendron whitefly

• Categories: Ornamentals Rhododendron Rhododendron Insects Shrubs
• Last review date: 2025-06-27 10:01

Biology

Whiteflies are small white insects that hold their wings rooflike over their abdomens rather than flat like true flies.

Infested leaves, usually the tender young leaves at the branch tips, are mottled yellow on the upper surface, and the margins often curl. Rhododendron whiteflies often leave white powdery residues on the leaf surface. Rhododendrons with smooth surfaces underneath the leaf are most affected.

Whiteflies can produce large amounts of sticky honeydew, which can develop a heavy coating of black sooty mold.

The rhododendron whitefly is mainly an aesthetic pest, although heavy infestations can damage susceptible plants.

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!

• Do not overfertilize. Whitefly numbers increase with increasing foliar nitrogen levels. If necessary, switch to a slow-release fertilizer and/or one with less nitrogen.
• Lightly vacuum plants in the early morning to remove cold, slow-moving whiteflies.

Chemical Management

• Several applications may be necessary about 7 days apart.
• Apply when first 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.