The western tussock moth is considered a pest and commonly found on the Pacific coast from southern California up to British Columbia.
This pest feeds on willow, hawthorn, manzanita, oak, walnut, crabapple, pyracantha, California holly, coffeeberry, and other plants.
In southern California, two generations may occur each year. Other areas may have only one generation per year. In northern California, this insect lays eggs in summer in felt-like masses, usually on old cocoons. These grayish-brown masses are typically 1/4” to 3/8” in diameter. The eggs hatch early the following spring. The larvae (caterpillars) are attractively colored, with spots of red and yellow, and four rounded, brush-like tufts on their backs. The young larvae skeletonize the leaves, while more mature larvae eat entire leaves. They remain caterpillars for 40 to 60 days and can become a nuisance when they wander to find a place to pupate. The adults emerge the same year as the cocoons are formed (pupation). The adult females are wingless and silvery-gray, while the males have wings and are grayer in color.
If necessary, pesticide applications during the early stages of larval feeding may help control the pest. Ask an arborist about the best treatment options for your property.