WSU Extension

Hortsense

Caption: Overwintering lecanium scale on apricot
Photo by: M. Bush
  
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Apple : Lecanium scale
(revision date: 2/14/2019)


Biology
Lecanium scales are shiny brown insects found on twigs. Adults are 1/8"-1/4" in diameter and roughly turtle-shaped. They may have light markings or appear somewhat waxy. Crawlers (immature scales) are flatter. Scales produce large amounts of honeydew, a sweet, sticky material which may attract ants or become covered with a growth of dark sooty mold. Branches with heavy scale infestations may be wilted, yellowish, or show other signs of stress. New growth may be stunted or lacking. Lecanium scale is a common pest in the landscape, infesting many plants including dogwood, maple, rhododendron, willow, and most fruit trees.
Management Options

Non-Chemical Management
  • Natural enemies such as ladybird beetles and green lacewings help control scale populations. Avoid use of broad-spectrum insecticides which kill these and other beneficial insects.
  • Control honeydew-feeding ants which may protect scales from predators.
  • Hand-wipe to help control minor infestations.
  • Prune and destroy heavily infested branches, when practical.
Select non-chemical management options as your first choice!

Chemical Management


Oils are effective in the dormant or delayed dormant period. Apply spray oils March to April. Use superior type oil sprays only on overwintering nymphs. 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.
  • R-T-U Year-Round Spray Oil
    Active ingredient: oil/pet distillate  |  EPA reg no: 6218-78
  • Safer Brand Garden Defense Multi-Purpose Spray Conc [Organic]
    Active ingredient: clarified hydrophobic extract of neem oil  |  EPA reg no: 70051-2-42697
  • This list may not include all products registered for this use.
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Caption: Overwintering lecanium scale on apricot
Photo by: M. Bush
Caption: Lecanium scales
Photo by: R.S. Byther