Rhododendron: Azalea bark scale

categories: Ornamentals Rhododendron Rhododendron Insects Shrubs

revision date: 2024-06-05 08:28

Azalea bark scale and sooty mold.
Azalea bark scale and sooty mold
Photo by: A.L. Antonelli


The azalea bark scale is a soft scale resembling mealybugs. Red females cover themselves and their eggs with a white, waxy protective coating. Cottony masses of the scales are often located on twigs and in the forks of the branches. Sticky honeydew is excreted by the pests, and may have black sooty mold growing on it.

Management Options

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

Non-chemical Management

Select non-chemical management options as your first choice!

  • Keep plants healthy. Vigorous plants are more able to tolerate scale damage.
  • Several species of ladybird beetles and parasitic wasps help control scale populations. Avoid use of broad-spectrum insecticides which can kill these predators.
  • Prune and destroy leaves or stems that are severely affected to help control minor infestations.
  • Hand-picking to remove insects may control small infestations.
  • Provide proper plant nutrition. Like aphids, scale populations increase with high plant nitrogen levels. If necessary, change to a slow-release fertilizer or one with less nitrogen.

Chemical Management

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

  • Scout for crawlers.
  • Apply to control the immature crawler stage, usually in late spring to early summer.
  • 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.