Rhododendron: Lecanium scale
Photo by: R.S. Byther
Biology
Lecanium scale adults are found on the twigs in late spring. At this stage they are usually brown or mottled brown and white bumps on the stems.
During the summer and fall, scale nymphs can be found on the foliage and are flat and light brown. The partially developed nymphs overwinter in crevices in the bark.
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!
- Prune to remove heavily infested branches.
- Hand removal of adult scales (when practical) can reduce populations to tolerable levels.
- Keep dust down and plant flowering plants to attract natural predators such as ladybird beetles.
- Provide proper nutrition for plants. High levels of nitrogen in the foliage may encourage scale reproduction. If necessary, switch to a slow-release formula or one with less nitrogen.
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.
- 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.