WSU Extension

Hortsense

Caption: Azalea bark scale and sooty mold
Photo by: A.L. Antonelli
  
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Azalea : Azalea bark scale
(revision date: 2/14/2019)


Biology
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

Non-Chemical Management
  • Provide proper culture, including fertilization and irrigation. Healthy 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.
  • Where the infestation is limited, it may be possible to hand-wipe or prune and destroy stems that are severely affected.
Select non-chemical management options as your first choice!

Chemical Management


Apply treatment to control young crawlers usually in early July, but may also be controlled through September. Treatment can also be made in March and early April. Monitor populations so that applications can coincide with egg hatch. Test for sensitivity on azalea before applying insecticidal soaps.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bonide Systemic Insect Control
    Active ingredient: acephate  |  EPA reg no: 239-2461-4
  • Hi-Yield 55% Malathion Spray
    Active ingredient: malathion  |  EPA reg no: 7401-10-34911
  • Hi-Yield Dormant Spray
    Active ingredient: oil/pet distillate  |  EPA reg no: 7401-428
  • Ortho Max Malathion Insect Spray Conc
    Active ingredient: malathion  |  EPA reg no: 239-739
  • R-T-U Year-Round Spray Oil
    Active ingredient: oil/pet distillate  |  EPA reg no: 6218-78
  • Safer Brand Insect Killing Soap Conc II [Organic]
    Active ingredient: potassium laurate  |  EPA reg no: 42697-60
  • This list may not include all products registered for this use.
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Caption: Azalea bark scale and sooty mold
Photo by: A.L. Antonelli