Cottony Maple Scale

Pulvinaria innumerabilis

HOST Hackberry, honeylocust, linden, maple, boxelder

DAMAGE/SYMPTOMS The scale damages its host plant by sucking the sap from the tree, which can cause dieback of twigs and branches. It secretes excessive honeydew as a waste product. This can be unattractive underneath the tree, can attract nuisance wasps, and can also attract sooty mold.

LIFE CYCLE The scale overwinters as a fertilized adult female on branches of the tree. Feeding activity resumes in the spring. A waxy, cottony egg sac is produced in late spring. Egg hatch occurs in late June through July, and the crawlers then move to the leaves.

MANAGEMENT Cottony maple scale is attacked by several natural enemies, including lady beetles, predatory flies and wasps, and sparrows. Dormant oils can be used in early spring prior to bud break. The crawlers are clear and flattened and can be monitored with a white piece of paper placed underneath the vegetation. Contact insecticides, such as bifenthrin and permethrin, can be applied to the crawler stage of the scale (late June through July). Systemic insecticides, containing the active ingredients imidacloprid and dinotefuran, can be applied in the spring.

A Cottony maple scale on maple branch. B Cottony maple scale adult.