The Asian gypsy moth (AGM, including 

Lymantria dispar asiatica, Lymantria 

dispar japonica, Lymantria albescens, 

Lymantria umbrosa, and Lymantria

postalba) is an exotic pest not known 

to occur in the United States. Although 

in many ways similar to the European 

gypsy moth, AGM larvae feed on a much 

broader range of plant species, covering 

over 100 botanical families. This broad 

range of possible host plants, combined 

with the female’s ability to fly long

distances, could allow AGM to spread 

rapidly. Large infestations of AGM can 

completely defoliate trees, leaving them 

weak and more susceptible to disease 

or attack by other insects. If defoliation 

is repeated for 2 or more years, it can 

lead to the death of large sections of 

forests, orchards, and landscaping. Any 

introduction and establishment of AGM 

in the United States would pose a major 

threat to the environment and the 

urban, suburban, and rural landscapes.

Since 2009, the U.S. Department of 

Agriculture (USDA), in partnership 

with the Canadian Food Inspection 

Agency, has worked with foreign trading 

partners to monitor populations of AGM 

and inspect ships before they leave to 

certify that they are free of AGM life 

stages. Ships are also inspected for 

AGM when they arrive at U.S. ports. 

Although these preventive measures 

are effective, occasional introductions 

of AGM have occurred. When AGM 

is detected, USDA works with other 

Federal and State agencies to evaluate 

the infestation and take appropriate 

actions to keep it from spreading.

Background

AGM was first identified in North 

America in late 1991 near the Port 

of Vancouver in British Columbia, 

Canada. Moths were discovered shortly 

thereafter in Washington, Oregon, and 

British Columbia.

Ships infested with AGM egg masses 

from ports in eastern Russia probably 

introduced the pest to North America 

while visiting ports on the West Coast.

Scientists believe that, while the ships 

were docked, larvae hatched from the 

eggs and were blown ashore. USDA 

and State officials eradicated these 

infestations in the Pacific Northwest 

through trapping and treatment 

activities.

In 1993, another infestation, this 

time in Sunny Point, NC, occurred 

after moths emerged from a ship 

carrying infested cargo containers 

from Germany and then flew into the 

surrounding area. AGM was not known 

to occur in Europe until tracebacks of 

this introduction provided evidence 

of other populations there. Between 

1991 and 2014, AGM was detected and 

eradicated on at least 20 occasions in 

locations across the United States.

The most recent AGM detections 

occurred in 2015 when male moths 

were caught in survey traps: 10 moths 

in Washington State, 2 moths in 

Oregon, 1 moth in Georgia, and 1 moth 

in South Carolina. Ongoing surveys in 

those States and Oklahoma will help 

determine whether infestations are 

Asian gypsy moth larva (above) and eggs (below) 

(John Ghent, USDA Forest Service, Bugwood.org)

present and what followup actions may 

be needed to address them.

Several USDA pest risk assessments 

over the years have concluded that, 

because of similarities between Asian 

and North American ecosystems, 

left unaddressed, the AGM has great 

potential for colonization in North 

American forests.

Potential Damage

If established in the United States, 

AGM could cause serious, widespread 

damage to our country’s landscape and 

natural resources. Each AGM female 

can lay hundreds of eggs in fuzzy egg 

masses that, in turn, yield hundreds of 

voracious caterpillars that may feed on 

hundreds of tree and shrub species. 

AGM caterpillars can defoliate plants 

Asian gypsy moth adults 

Pest Alert Animal and Plant Health Inspection Service

Plant Protection and Quarantine 

Asian Gypsy Moth

United States Department of Agriculture
at an alarming rate. This defoliation 

can severely weaken trees and shrubs, 

killing them or making them more 

susceptible to diseases and other pests 

and destroying habitats for mammals 

and birds. Caterpillar silk strands, 

droppings, destroyed leaves, and dead 

moths would also be a nuisance in 

homes, yards, and parks.

Comparing Gypsy Moth Pests

The AGM is similar to the European 

gypsy moth found in the northeastern 

United States and southeastern Canada. 

Like the European gypsy moth, AGM 

prefers forest habitats and can cause 

serious defoliation and deterioration of 

trees and shrubs. The European gypsy 

moth has more than 300 known host 

plants but prefers oak. The AGM has 

a much broader host range, including 

larch, oak, poplar, alder, willow, and 

some evergreens.

In the eastern United States, European 

gypsy moths defoliate an average of 

700,000 acres each year, causing 

millions of dollars in damage. If AGM 

were to become established in our 

country, the damage could be even 

more extensive and costly.

Unlike the flightless female European 

gypsy moths, AGM females are active 

fliers. Their ability to fly long distances 

makes it probable that AGM could 

quickly spread throughout the United 

States. In contrast, the European gypsy 

moth has taken more than 140 years 

(since 1869) to spread throughout the 

United States from the Northeast to the 

Southeast and the Midwest.

Life Stages

The AGM matures through four life 

stages: egg, larva (caterpillar), pupa 

(cocoon), and moth. AGM egg masses 

may be found on tree trunks, limbs, 

or leaves, as well as on stones, walls, 

logs, lawn furniture, and other outdoor 

objects. Each egg mass can contain 

hundreds to more than 1,000 eggs. The 

mass is covered with buff or yellowish 

fuzz from the abdomen of the female. 

While the velvety egg masses average 

1 1⁄2 inches long and three-fourths of 

an inch wide, they are often as small 

as a dime.

AGM eggs begin hatching into caterpillars 

in the spring. All of the damage caused 

by the AGM happens during the 

caterpillar stage, as the insects feed 

on leaves during this active period of 

growth. Once AGM caterpillars stop 

feeding, they enter the pupal stage. 

This stage typically begins in June or 

July. Because egg hatch and pupation 

depend on weather and temperature, 

they may occur earlier or later in 

different areas. Adult moths emerge 

from their dark-brown pupal cases in 

10 to 14 days. Adult males have 

grayish-brown wings and a wingspan 

of 1 1⁄2 inches. Adult female moths are 

white and larger, with wingspans of 

3 1⁄2 inches or more.

AGM do not feed in the moth stage 

(which lasts 1 to 3 weeks); they 

only mate and lay eggs. Eggs are 

laid between June and September, 

depending on weather and location. 

The eggs remain dormant during the 

winter and develop and hatch the 

following spring.

How AGM Can Spread

AGM infestations spread in several 

ways. Adult female moths may fly to 

previously uninfested areas to lay eggs. 

Or, newly hatched AGM caterpillars 

may climb to tree crowns, where the 

wind picks up their silken threads and 

carries them to other areas.

In addition, people can inadvertently 

transport egg masses or pupae. AGM 

egg masses tolerate extremes in 

temperature and moisture and travel 

well on logs, lawn furniture, nursery 

stock, pallets, shipping containers, and 

the hulls and rigging of ships.

Protecting the Country 

From AGM

The first line of defense against AGM 

is USDA’s work to prevent this pest 

from reaching the United States. In 

partnership with Canada, the USDA 

works with China, Japan, South 

Korea, and Russia to make sure AGM 

population levels are monitored at 

and near ports. Ships and cargo 

headed for the United States are 

inspected for AGM and certified as 

pest-free before departing. On arrival, 

ships and cargo undergo another 

inspection to ensure that AGM is not 

present. These protective measures are 

highly effective but, on rare occasions, 

AGM introductions do occur. A robust 

survey program at and near ports 

of entry helps detect any possible 

introductions at an early stage—when 

eradication efforts are most effective 

and least costly.

What You Can Do

You can support efforts to detect and 

manage AGM by:

• Reporting any findings of egg masses 

on trees, lawn furniture, fences, 

walls, or elsewhere to Federal or 

State agriculture officials.

• Cooperating with any restrictions in 

your local area that might be imposed 

because of an AGM detection.

• Allowing authorized agricultural 

workers access to your property 

to place and inspect insectmonitoring traps.

To learn more, contact your:

• Local Extension office

www.nifa.usda.gov/Extension

• State Plant Regulatory Official

www.nationalplantboard.org/

member

• Nearest USDA Animal and Plant 

Health Inspection Service office

www.aphis.usda.gov/planthealth/

sphd

APHIS 81-35-027

Issued April 2016

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