Apple: San Jose scale
categories: Apple Apple Insects Tree Fruits
revision date: 2024-04-08 11:46
Photo by: M. Bush
Biology
San Jose scale is an armored (hard) scale found on many deciduous trees and shrubs including apple, cherry, elm, maple, poplar, and willow. The scale insects are about 1/16″ in diameter. The female is gray with a yellow spot in the center. The yellow crawlers are easily spread by wind, birds, or people. San Jose scale may be found on twigs, branches, leaves, and fruit. Heavily infested branches or entire trees may wilt and appear water-stressed. Severe infestations can cause twigs and branches to die back. Repeated infestations can kill trees. Infested fruit develop sunken spots surrounded by reddish areas. The scale overwinters as black immature scales on bark.
Management Options
Use Integrated Pest Management (IPM) for successful plant problem management.
Non-chemical Management
Select non-chemical management options as your first choice!
- Provide proper plant care. Healthy plants are more tolerant of insect damage.
- Prune and destroy localized infestations, when practical.
- Natural predators and parasites help control scale populations, but may not prevent damage in severe infestations. Avoid use of broad-spectrum insecticides which kill beneficial insects.
- By late April, begin monitoring for crawlers by using double-sided sticky tape.
Chemical Management
IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.
- Apply oils in early spring just prior to bud swelling.
- 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
Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
Additional Images
Photo by: K. Grey
Photo by: A.L. Antonelli