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

Non-Chemical Management

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.

Select non-chemical management options as your first choice!

Chemical Management

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

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.

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

Bayer Advanced Vegetable & Garden Insect Spray RTS
Active ingredient: cyfluthrin | EPA reg no: 72155-39
This list may not include all products registered for this use.

Images

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Caption: Rhododendron whitefly Photo by: A.L. Antonelli

WSU Extension

Hortsense