Gypsy Moth
The gypsy moth (Lymantria dispar) does not belong in Wisconsin or anywhere in North America. It is an invasive pest from Europe that has established in the northeastern states, parts of Canada and the upper Midwest, including the eastern half of Wisconsin. Today, the gypsy moth continues to move westward into the backyards and forests of the state.
What is the concern?
The gypsy moth is an unusual species. Its population goes through cycles of abundance—from typically low numbers to short-lived explosions in what is called an outbreak. During outbreaks, the hordes of gypsy moth caterpillars strip entire forests of leaves. Trees that were healthy typically can survive a single defoliation, but weak or stressed trees can be killed. Outbreaks can be localized to a single woodlot or stretch over thousands of acres. During outbreaks, the leaves of most types of trees will be eaten because the gypsy moth caterpillar is not a fussy eater. It will feed on both broad-leaved trees and evergreens. The tree species it likes the best such as oaks, birch and aspen will be the worst defoliated. However, most trees in Wisconsin forests will be affected to some degree during outbreaks.
Wisconsin’s Response
Once the gypsy moth is established, it will be part of our natural community forever, and we will have to manage it when it threatens forests we value. However, there are a number of steps that can help delay its establishment and slow down its westward progression into new areas. When we slow the pest down, we buy more time free of this pest and the damage it does for areas not yet infested.
The Department of Agriculture, Trade and Consumer Protection (DATCP) works to delay establishment of gypsy moth by two means: the Slow the Spread (STS) Program and regulation to prevent spread on products like nursery trees or logs. As part of the STS program, DATCP detects spread of the pest trapping and egg mass surveys. This information is used to target aerial insecticide treatments. DATCP also deals with quarantine issues and regulations for nurseries, paper and lumber mills and movers to help prevent accidental spread of gypsy moth.
Where the gypsy moth is established and outbreaks threaten to cause damage to our forests the Wisconsin Department of Natural Resources conducts a separate, voluntary, cost-shared aerial spraying program to suppress outbreaks of gypsy moth in quarantine counties. DATCP usually does not conduct aerial spraying in quarantine counties.
Identifying Gypsy Moth
The gypsy moth has four life stages: egg mass, caterpillar, pupa and moth. It is only in the caterpillar stage of life that the gypsy moth is destructive and a potential health concern.
What If I Find Gypsy Moth?
If you find gypsy moth west of the quarantined area, report your find to DATCP (1-800-642-MOTH) as this information could be used by the STS program.
If you find gypsy moth within the quarantined area, there may be no need for immediate concern. In most years, gypsy moth will be at low levels and pose no threat. If populations are increasing to damaging levels, however, you may want to take action. Go to
gypsymoth.wi.gov for directions on monitoring gypsy moth using predictive surveys and options for managing the pest for yards and woodlots
Other Resources
See a listing of links that give additional information about gypsy moths.
History of the Gypsy Moth
In 1869, French lithographer and amateur entomologist Etienne Leopold Trouvelot imported gypsy moths from Europe to Medford, Mass. Trouvelot hoped to breed them with silkworms to produce a hardier species. Unfortunately, a few gypsy moths escaped and had since spread westward throughout the northeastern states, portions of Canada and into the upper Midwest. It was first found in Wisconsin in 1971. Gypsy moth is usually spread unintentionally on campers, nursery stock and even patio furniture infested with egg masses.
For more information, call toll free 1-800-642-6684 and select option 3, or e-mail
[email protected].
