Spongy Moth

This fact sheet contains information on the Spongy moth (Lymantria dispar), previously known as Gypsy moth, and contains information on a series of practices to reduce defoliation by Spongy moth caterpillars on residential properties. However, the control measures described herein may not be satisfactory within, or adjacent to, areas of high spongy moth density. Due to the extensive impact of Spongy moth, quarantine areas have been delineated by the United States Department of Agriculture (USDA). Those who are in a quarantine area and plan to move outdoor household items to a non-quarantine area must inspect objects for possible Spongy moth exposure before moving. More information pertaining to quarantine areas can be found at aphis.usda.gov.

Life Cycle

The Spongy moth develops in four stages: egg, larvae (caterpillars), pupa (transformation stage), and adult (moth). Only the larval stage is destructive. Eggs are deposited in a cluster called an "egg mass" from June to August. The oval egg masses vary in size but are generally about 1 inch long and ½ inch wide. Egg masses are covered with buff-colored hairs from the female’s body. Trees, stones, buildings, and most shaded objects are suitable sites for egg deposition. The egg stage lasts through the remainder of the summer, fall, and winter.

Eggs usually begin to hatch in late April and continue to hatch for about two weeks. Young caterpillars (larvae) are hairy and can be carried for considerable distances by the wind. They feed from late April to early July. Full-grown caterpillars may be 1 ½ to 2 ½ inches long with several pairs of dots along the top of their bodies. The first five pairs of dots are blue; the last six pairs are red.

Spongy moth caterpillars have a voracious appetite and can cause extensive defoliation of trees. Some favored host trees include apple, aspen, birch (except for black and yellow), boxelder, larch, linden, mountain ash, oaks, speckled alder, sweetgum and willow; however, other hardwood species may be attacked. Hemlock, pine, and spruce may be damaged by late-stage caterpillars.

It is not uncommon to observe large numbers of "migrating" caterpillars crossing roads and on the sides of dwellings and other stationary objects. Migrating caterpillars can stain paint on houses and when handled, their body hairs can irritate the skin.

Caterpillars enter the pupal stage during June, and adult moths emerge after 10 to 14 days. Male moths are brown with blackish bands across the front pair of wings. They can be seen flying while searching for females, especially up and down the trunks of trees. Female moths have white wings with black markings, but do not fly. After mating, the female deposits her eggs. There is only one generation per year.

Control

Egg masses can be destroyed from August to late April by scraping them off with a penknife or a thin putty knife. Collect the egg masses into a container with warm soapy water or place them into a sealed plastic bag in the sun or burn them. All egg masses that fall to the ground while scraping should also be collected and burned.

From mid-to-late May, burlap strips tied to the trunks of trees will capture some Spongy moth caterpillars. Each strip should be at least 18 inches wide and long enough to encircle tree trunks. Place a strip around the tree and secure the middle with twine. Fold the upper edge of the burlap down over the twine to form a skirt-like band. Inspect all burlap strips every day. Remove and kill all caterpillars hiding in the strips by hand. The bands can be removed in late July. Banding of trees with sticky material or burlap strips will not guarantee caterpillar control because young caterpillars may be blown into trees from adjacent areas. Sticky band traps are not recommended due to the potential bycatch of unintended species of animals such as beneficial insects, birds, mammals, and reptiles.

When young caterpillars begin to feed in May, trees can be protected from defoliation by applying insecticides. Compressed air (or knapsack) sprayers can be used by homeowners for small trees. A trombone sprayer is necessary for small trees (about 15 feet). Thorough spray coverage of foliage is necessary for adequate control. Tall trees require the use of specialized equipment such as a mist blower or a high-pressure, high-gallonage hydraulic sprayer. A licensed tree expert or professional landscape maintenance firm usually has the proper equipment and experience needed to service home grounds and should be hired to do so.

Some insecticides labeled for Spongy moth control are listed below*:

Material and Formulation	Amount for Hydraulic Application			Mist Blower
	100 gallons	3 gallons	1 gallon	50 gallons
Acephate (Orthene) (Application by Certified Applicators only)
75% Soluble powder	2/3 lbs.	-	-	2/3 lbs.
Bacillus thuringiensis
Thuricide HPC	2 qts.	3 fluid oz.	1 fluid oz.	10 qts.
Dipel Pro DF	¼ - 1 lbs.	9 tbsp.	3 tbsp.	5 lbs.
Javelin WG	0.12–1.25 per acre	3 tsp.	1 tsp.	-
Cyfluthrin (Decathlon, Tempo) (Application by Certified Applicators only)
20.0% WP	1.3 oz.	-	-	-
10.0% WP	1.9–6.7 oz.	-	-	-
Dimilin (Application by Certified Applicators only)
25W 1 to 4 ounces in sufficient water volume (1.5 to 10.0 gallons/acre) to achieve uniform coverage of foliage. Limit to 1 application/year.

References

• US Department of Agriculture. 2024. Spongy Moth Program Manual (PDF). Last modified September 26, 2024.
• US Department of Agriculture. 2025. Spongy Moth. Last modified July 30, 2025.
• US Department of Agriculture. n.d. Spongy Moth Quarantine. Accessed June 13, 2025.
• US Department of Agriculture, US Forest Service. 2024. Flight in Female Asian Spongy Moths. Last modified October 31, 2024.

This fact sheet has been updated from the original version written by George C. Hamilton, Ph.D., Extension Specialist in Pest Management and Louis M. Vasvary, Ph.D., Extension Specialist in Entomology (deceased).

August 2025