Cottony Maple Leaf Scale: Appearance, Territory, Damage and Life

Latin name: Pulvinaria Acericola

Appearances: Pulvinaria Acericola (cottony maple leaf scale) is a little brown scale insect with a flattened body that is about 1/8″ long. Cottony maple scales are small, flat, oval-shaped brown insects with no visible legs, antennae, or wings when mature. They can range in size from 14 to 38 inches in diameter and are securely adhered to the twigs and branches of various trees.

Host plants: P. Acericola can be found on all maple species (Acer spp.), but Silver Maple is its preferred host. Honey and black locust, white ash, Euonymus, oak, boxelder, dogwood, hackberry, sycamore, beech, elm, willow, basswood, and poplar are also reported to be suitable food sources.

Territory: In Ohio, the Cottony Maple Leaf Scale (Pulvinaria Acericola) was once a common maple pest. However, until last year, when noticeable populations were observed in the state’s central and southwest regions, this natural “soft scale” had practically vanished from our radar.

Damage insect caused: Because of the high population, branches might become fully flooded with females and their white egg masses. When feeding crawler infestations are severe, leaves may become yellow and fall off prematurely, resulting in individual branch dieback. Heavy infestations have been known to harm stressed or weakened trees on rare occasions. While eating on leaves, the crawlers, or young scale insects, produce a lot of honeydew. Honeydew accumulates on leaves and branches, attracting bees, wasps, and ants to feed.

Life cycle and habits: Females produce ovisacs, which are white, cottony egg masses, over a period of many weeks when they reach maturity. The “cotton” is actually a waxy fluid that surrounds the ovisac, which can hold up to 1,500 eggs. Scale crawlers are the juvenile nymphs that hatch from these eggs between mid-June and August. These tiny crawlers have two distinct eyes, short antennae, and tiny legs. They are small, flat, oval insects with two distinct eyes, short antennae, and tiny legs.

Crawlers walk onto the leaves and attach themselves to the primary leaf veins, which are usually on the underside. The nymphs here create a lot of honeydew and only molt once a year. The scales are now divided into two types: a translucent white to pink form and a larger, flat tan form. The scales on the left and right are male and female scales, respectively. The male scales emerge in September as small winged gnat-like insects that fly around the leaves looking for females.