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Description of kermes scale
Kermes scales feed on oaks and can range in size from about 1/8 - 1/4 inch in size, and are smooth and globular. Colors can range from creamy white to brown depending on the scale species. Kermes scale look a bit like a bud or a gall, but unlike galls or leaf buds kermes scales can be easily removed from the plant.
Life cycle of kermes scale
Kermes scales overwinter as crawlers on the bark of infested trees. Crawlers are what hatched from scale eggs and they crawl around (thus their name). Once the
female scale has found a good place to feed it settles on the branch and no longer moves. The scales feed on the oak with piercing-sucking mouthparts that suck out plant sap.
Damage caused by kermes scale
In Iowa the kermes scale that occurs on bur oak causes the most damage. On infested trees large numbers of scale can be found feeding on the new branches and leaves causing the growth to be deformed and stunted.
Management of kermes scale
Predators and parasites can help keep populations in check, but if scales continue to be a problem over several years treatment is warranted. Be sure to select a product labeled for kermes or soft scales. Treatments include dormant oil sprays before trees leaf out or contact insecticides applied when crawlers are active in the spring. Systemic insecticides will also provide good control of kermes scale.
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