WSU Extension

Hortsense

Caption: Lecanium scales
Photo by: R.S. Byther
  
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Holly : Lecanium scale
(revision date: 2/14/2019)


Biology
Lecanium scales are shiny brown insects found on leaves and twigs. Adults are 1/8"-1/4" in diameter and roughly turtle-shaped. 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. Heavily infested plants may appear yellowish or wilted, or show other signs of stress. New leaves may be stunted. Lecanium scale is a common pest in the landscape, infesting many plants including dogwood, maple, rhododendron, willow, and 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.
  • 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


Scout for crawlers. Insecticide applications can be effective when applied to control the immature crawlers stage, usually in late spring to early summer. Oils are effective in the delayed dormant period. 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.
  • All Seasons Horticultural & Dormant Spray Oil Conc [Organic]
    Active ingredient: oil/pet distillate  |  EPA reg no: 4-80
  • Bonide Systemic Insect Control
    Active ingredient: acephate  |  EPA reg no: 239-2461-4
  • 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: Lecanium scales
Photo by: R.S. Byther