Poplar: Oystershell scale
Photo by: Unknown
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
See "Using Integrated Pest Management (IPM) in the Landscape" for successful problem management techniques.
Non-chemical Management
Select non-chemical management options as your first choice!
- 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.
Chemical Management
IMPORTANT: Always read and follow label directions when working with pesticides.
For more information on using pesticides visit :
- 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.
Approved Pesticides
If you choose to use a pesticide, some examples of products that are legal in Washington are listed below. Some products are labeled for just INDOOR or just OUTDOOR use, or may allow both uses. Be sure to choose a product appropriate for your situation. Always read and follow all label directions.
WSU Extension programs and employment are available to all without discrimination.
Evidence of noncompliance may be reported through your local Extension office.