Oystershell Scale
About Oystershell Scales
Lives on ash, maple lilac, and many other species of hardwood trees and shrubs.
Crawlers are very small, flattened and pale yellow or orange. Scales resemble tiny oyster shells, are gray to purplish-brown, and are about 3 mm long at maturity.
Scales overwinter as eggs beneath female shells. Crawlers emerge in May or June, migrate to a feeding site, and molt to the immobile scale form. Nymph and adult oystershell scales feed on the sap of twigs, branches, and thin-barked stems.
Branch and tree mortality may result from large scale infestations.
To Control
Spray twigs, branches, and stems with superior oil in the spring before buds expand or with malathion or acephate when crawlers are present. During winter, scrape parent scales filled with overwintering eggs from infested tree parts by lightly rubbing with a plastic or TeflonŽ dish pad.