Kermes Scale on Oak trees
Kermes scale is an insect pest of pin, red and Gambel oak. The symptoms of Kermes scale infestation include leaves changing color, branch tips turning brown, sap oozing, and twig dieback. Yellowjackets may be attracted to and feed on adult female scales.
The tan to brown female scales are 1/4” in diameter, round, immobile and found at the base of leaf stems. Adult female scales are difficult to see because they look very similar to buds. Eggs hatch in September and October.
Kermes scale is aggressive and can cause significant damage in oak and treatment is necessary when infestations cover most of the tree. Kermes scale control is most effectively applied in either the fall crawler stage or during winter. Crawlers may be controlled with various pyrethroid insecticides and imidacloprid (Bayer® Tree & Shrub Insect Control). Over-wintering scales may be controlled with horticultural oil (such as All Seasons® or fertilome Dormant Oil Spray). If you decide control is warranted, learn more about pesticide safety here http://www.ext.colostate.edu/ptlk/1429.html or choose a licensed pesticide applicator.
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Updated Tuesday, October 13, 2015