USDA Forest Service

Gypsy Moth In North America


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United States Department of Agriculture Forest Service.

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Gypsy Moth Management

Because the gypsy moth has many undesirable effects on trees and forests, efforts are made to manage the problem. Eradication and Slow the Spread are methods used to prevent or postpone the establishment of gypsy moth populations in portions of the country where it currently does not exist. Suppression, silviculture, and biological control are methods used to manage established gypsy moth populations.


In states that currently do not have established gypsy moth populations (e.g. California, Kentucky, Minnesota) grids of pheromone traps are used to detect new, isolated populations. These populations are usually the result of the accidental introduction of gypsy moth life stages on articles such as recreational equipment, fire wood, or nursery material. Pheromone traps are very sensitive methods for detecting gypsy moth populations, even when they exist at such low densities that egg masses or caterpillars may not be found. When males are trapped for several years at the same location, this is evidence of a reproducing population. In these cases, an effort is usually made by state and federal agencies to eradicate (totally eliminate) this infestation. Eradication methods vary, but sometimes include spraying with chemical or biological pesticides, mating disruption, or mass-trapping.

Slow the Spread

Gypsy moth populations in N. America are slowly expanding their range. Because, it may take many years before the gypsy moth range spreads to include all of N. America, there is logic in attempting to slow the rate of spread into uninfested areas. Doing so will reduce gypsy moth impacts in those areas. Currently, the USDA Forest Service is undertaking a major effort to slow gypsy moth spread. Scientists believe that it is impossible to stop gypsy moth spread but evidence to date indicates that it is possible to reduce the rate of spread by 50% or more. This is accomplished by using grids of pheromone traps along the expanding front to detect isolated colonies. These colonies are then suppressed or eradicated using environmentally benign methods. More information about this method can be found at the Slow the Spread Project homepage.


Most of the negative impacts associated with the gypsy moth occur at high densities. Therefore, a common approach to gypsy moth populations is the direct suppression of populations in order to minimize these effects. These efforts are sometimes carried out by individual homeowners using ground applications of pesticides to individual trees, aerial application of pesticides by private contractors, or aerial applications of pesticides in cooperative state/federal programs. Materials used in these treatments include the chemical pesticide "Dimilin", or the biological pesticides, Bacillus thuriengensis and "Gypchek", a formulation of the naturally occurring gypsy moth virus.

Information about these programs can be obtained by contacint your local county extension agent. Information can also be obtained from USDA Forest Service Forest Health Protection group.

Biological Control

The gypsy moth has a variety of natural enemies (predators, parasites, and diseases) that naturally control populations. Research scientists are still searching for natural enemies in the native range of the gypsy moth that might be introduced to N. America for control purposes. Some effort is also underway to develop methods to increase the effectiveness of natural enemies that are already established.


The gypsy moth can have substantial effects on the growth and survival of forest trees. One approach to managing this problem is to use silvicultural methods to reduce the susceptibiltiy (defoliation potential) and vulnerability (tree mortality) of forests to the gypsy moth. This can be accomplished by selectively cutting host trees preferred by the gypsy moth and/or cutting trees that are in poor condition and likely to die following defoliation. More information on silviculture can be found at the Gypsy Moth Silvicultural Experiment Tour

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Last modified 10-29-03 by Sandy Liebhold .

USDA Forest Service - Northeastern Research Station

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