WSU Extension

Hortsense

Caption: Oystershell scales
Photo by: Unknown
  
print version| pdf version| email url    

Poplar : Oystershell scale
(revision date: 2/14/2019)


Biology
Oystershell scales are usually found on trunks, branches, and twigs. They occur infrequently on the leaves. Immature scales, or crawlers, are yellowish to white. They are typically present around June. Crawlers develop pinkish shells later in the summer. The hard-shelled mature scale is approximately 1/8" long, striped with grayish and brown bands, and elongated like an oyster or mussel shell. Infested plants may show off-color foliage, wilting, or other signs of stress. Heavy infestations can severely weaken trees. Scales can be spread from plant to plant by birds, people, wind, or other insects. Broadleaf trees, shrubs, herbaceous plants, and fruit trees are commonly infested.
Management Options

Non-Chemical Management
  • Keep trees healthy to enable them to tolerate some damage.
  • In minor infestations, it may be possible to wipe scales off branches.
  • Where practical, prune and destroy heavily infested branches.
  • Natural enemies of scales help control populations, but usually not soon enough to prevent damage to plants. Avoid use of broad-spectrum insecticides which kill beneficial insects.
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.
  • Hi-Yield Dormant Spray
    Active ingredient: oil/pet distillate  |  EPA reg no: 7401-428
  • 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.
Images
    - hide images

+ Show larger images

 
Caption: Oystershell scales
Photo by: Unknown