Cottony Maple Scale: Appearance, Territory, Damage and Life

Latin name: Pulvinaria Innumerabilis

Appearances: Pulvinaria innumerabilis (cottony maple scale) is a little brown scale insect with a flattened body that is about 1/8″ long. The masses of eggs are noticeably white and cottony in appearance. Typically, each mass contains 1,000-1,500 eggs. Male scales are winged insects with small bodies. Females in their infancy are flat and unnoticeable. Females mature to be pale to dark brown, convex, and 3-6 mm long. The cottony maple scale is easily identified by the egg masses that appear on twigs and branches.

Host plants: The cottony maple scale is one of the most visible soft scale insects that attack ornamental deciduous trees. Silver maple, Acer saccharinum, is its preferred host.

Territory: Cottony maple scale (Pulvinaria innumerabilis) has been discovered in northern Illinois, according to sources.

Damage insect caused: Cottony maple scale insects cause very little damage in most cases. Although there may be some premature leaf drops, modest to moderate numbers do not harm trees.

The host tree is harmed when large populations of cottony maple scale drain the plant’s sap, causing branch and twig dieback. They eat within the vascular tissues, drawing plant fluids including nitrogen and water with their piercing-sucking mouthparts and excreting the excess as honeydew, a transparent, sticky liquid that coats tree limbs. Honeydew is generated in large quantities, causing the leaves to become covered in a grayish/black-colored sooty mold. Honeydew can be a nuisance since it coats patios, decks, and vehicles, and the sooty mold lowers the ornamental features of maples.

Life cycle and habits: Late spring is the best time to look for cottony maple scale. The female scales that spent the winter on the stems expand in June and begin generating a big, white, cottony egg sac. Egg sacs can be as big as a half-inch in diameter and hold up to 1000 eggs. Hundreds of egg sacs are stretched along the stems and branches, resembling popcorn. In “normal” populations, each twig crotch has one or a few egg sacs, whereas severe infestations may have enough egg sacs to completely cover most twigs. Insects that feed on sap are known as scale insects. Scales that have just developed crawl to the leaves and settle on the underside, where they begin a sedentary life of feeding on the tree’s sap. The scales mature on the leaves and mate in August or September, after which the females return to the twigs for the winter.