How to Identify and Control Spongy Moths

What You Can Do

There are ways to manage a spongy moth infestation. If the population is small, the egg masses can be destroyed by burning or crushing the eggs or placing them in a bucket of soapy water. Be careful when handling egg masses, because the hairs that cover them could cause an allergic reaction.

Homeowners and government agencies can also use other strategies, including a bacteria called Bacillus thuringiensis and tree banding, to control spongy moth infestations. Tree banding using burlap, tape and sticky substances can trap larvae moving up and down the tree trunk and capture several caterpillars, but generally does not significantly reduce the overall population.

What Orkin Does

If a homeowner thinks they may have a problem with spongy months, the first thing to do is contact your local extension service office for help in correctly identifying the pest. Every building or home is different, your Orkin Pro will design a unique moth treatment program for your situation.

What Do Spongy Moths Look Like?

Spongy moths’ characteristics make them easily distinguishable from other leaf-feeding caterpillars. They are dark in color and covered with hair. Their backs are lined with five pairs of blue dots and six pairs of red dots.

Male and female spongy moths look very different. The adult female moth is white and has wavy, dark bands that run from the front to the rear of the front wings. Adult females have a wingspan of about 2 inches but can only fly short distances. The female’s body is stout and densely covered with a patch of golden-colored hairs located on her head. Female spongy moths are also larger than males at 2 ½ inches long when mature. Male moths are only about 3/4 inch and have plain, brownish-gray wings with large, feathery antennae. The antennae, like many other species of moths, assist in locating females to mate with.

Spongy Moth Diet Facts

Spongy moth caterpillars prefer hardwood trees and are known to feed on more than 300 tree species. Larvae tend to feed primarily on oaks, birch, willows and alder. Older larvae prefer cedar, pine, spruce and fir.

Spongy moth eggs hatch and their larvae begin feeding at a time of year when many of their host trees are beginning to obtain leaf growth, usually around May. These caterpillars may completely defoliate trees by eating all of its leaves. Feeding normally begins at treetop, so spongy moth defoliation may go unnoticed on large, tall trees until the degree of defoliation becomes heavy. As the caterpillars age, older ones no longer remain in the upper regions of the tree, or the canopy, but move up and down the tree, seeking shelter sites on the ground and the tree trunk during the day and then moving back up the tree at night to feed on the leaves.

Life Cycle of a Spongy Moth

The spongy moth has four developmental stages – egg, caterpillar (larva), cocoon (pupa) and adult, that is completed within a year. The females lay an egg mass containing an average of 400-500 eggs covered with hairs that have dislodged and stuck to the egg mass from the female as she lays them. They typically lay their eggs underneath tree bark or in shaded areas. Spongy moths overwinter in their egg stage. Their eggs can attach to many outdoor objects, including trees and houses.

The eggs hatch into caterpillars during the larva stage. In caterpillar form, they can grow to approximately 38 to 50 mm in length. Full-grown larvae are easy to identify since they are very large (about 2 ½ – 2 ¾ inches) with long hairs, five pairs of blue bumps at their front and six pairs of red bumps at the rear of their back.

Behavior of Spongy Moths

The spongy moth was discovered in the United States in 1869 in Massachusetts. It spread throughout the northeast and has become one of the country’s most destructive hardwood forest pests. It is known to defoliate acres of forest and urban trees. The defoliation alters forest composition and destroys the habitats of many birds and mammals. It is native to Europe, southern Asia and northern Africa. In the United States, it most commonly is found in Pennsylvania, New Jersey, New York and Delaware.

How to ID and Prevent Spongy Moth Infestations

Spongy moths are voracious eaters, defoliating millions of trees annually. Some common signs of a spongy moth infestation are the defoliation of trees, holes in leaves and egg masses on tree trunks or any outdoor furniture.

Wrapping burlap around tree trunks provides a hiding place for larvae and makes monitoring their population easy. Barrier bands can also keep larvae from crawling up tree trunks. Large populations require more extensive treatment. Several insecticides have been used successfully in managing spongy moth populations. To reduce the chance of an infestation, make sure to water trees during a drought and increase soil moisture by placing mulch around the base of trees.