seal  Purdue News

March 1, 2004

As spring nears, so does gypsy moth season

WEST LAFAYETTE, Ind. - The approach of spring means gypsy moth season for homeowners across much of the northeastern United States, including northern Indiana, said Jodie Ellis, the exotic insects education coordinator at Purdue University.

gypsy moths
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Ellis said northern Indiana is the leading edge of the gypsy moth population in the state. Hoosiers who live in this area likely will find the Indiana Department of Natural Resources working in conjunction with the U.S. Forest Service to slow the spread of the gypsy moth.

"Two types of treatments are employed against gypsy moths," Ellis said. "The first uses Bacillus thuringiensis variant kurstaki (Btk). Btk is a bacteria that naturally occurs in the soil and effectively controls gypsy moth caterpillars, yet it is safe for humans and other animals."

Gypsy moth egg masses
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This treatment, which is aerially sprayed over the leading edge of an infestation in mid-May, is used where both male moths and egg masses are found.

The second treatment is used in areas where many male moths are found, but no egg masses or caterpillars have been observed. In those cases, pheromone sprays that mimic the smell of female gypsy moths are aerially applied in June.

"Since male moths emerge a few days before the females, they are overwhelmed by the immediate pheromone smell," Ellis said. "They are confused by the smell, cannot find real females and die before mating."

Because both types of sprays are meant to slow the spread of the moth, they are not used in areas behind the leading edge of an infestation where gypsy moths have become a permanent part of the landscape.

"Once established, it's impossible to eradicate the gypsy moth," Ellis said. "But if you slow their spread, you can give the forest a chance to gather its natural defenses against this pest."

Homeowners in areas scheduled for treatment will be notified by mail. Notices also are sent to local officials and news media. Ellis said that Btk has proven safe for humans and other mammals likely to come in contact with the material when it is applied outdoors. Btk applications generally take place during early morning hours when fewer people are likely to be outside.

"Although allergic reactions to Btk can occur, they are less likely and of a lesser magnitude than the allergic reactions people will experience during a gypsy moth infestation when they will be exposed to floating caterpillar hairs and fecal matter," said Cliff Sadof, a Purdue entomology professor.

After pheromone treatments, homeowners may notice a few tiny flakes on their car windshields. These can be safely rinsed off with water.

Gypsy moths feed on more than 500 species of trees and shrubs, but prefer oak trees. When populations explode, trees and shrubs can be completely defoliated. If defoliation occurs for more than a couple of years in a row, permanent damage can occur, Ellis said.

Homeowners can help slow the spread by being vigilant and removing egg masses and other life stages from firewood and nursery stock. It's also important to refrain from moving firewood and nursery stock from infested areas to regions where gypsy moths have not been found.

Gypsy moth egg masses are present from summer to late spring and can be found on tree trunks, branches and other stable surfaces such as rock walls or under window eaves. The egg masses are flat, tan, fuzzy and about the size of a quarter and can be removed with a paint scraper. Once removed, they should be soaked in soapy water for several days or saturated with soybean oil.

Pictures of egg masses are available at the Purdue Extension gypsy moth Web site in the biology and lifecycle section.

Homeowners who notice gypsy moth caterpillars in their trees can surround their tree trunks with folded over burlap bands to trap the pests. Ellis said that during the day, the caterpillars move down from the tree's leaves to find a cool, safe place to hide. Many of them will hide in the folds of burlap.

"Once a day in the afternoon the homeowner should remove the caterpillars from the burlap and soak their catch in soapy water for about 48 hours to kill them," she said. Instructions on attaching the burlap bands also can be found at the Web site.

Writer: Kay Hagen, (765) 494-6682,

Source: Jodie Ellis, (765) 494-0822,

Cliff Sadof, (765) 494-5983,

Ag Communications: (765) 494-2722; Beth Forbes,
Agriculture News Page

Related Web sites:
Purdue Extension Gypsy Moth Site

Indiana Department of Natural Resources Gypsy Moth Site


Male gypsy moths, shown at bottom right, begin emerging in June and can vary in size. Female gypsy moths emerge soon after the males. (File photo/U.S. Department of Agriculture's Animal and Plant Health Inspection Service Plant Protection and Quarantine and courtesy of

A publication-quality photo is available at

Gypsy moth egg masses can be found on tree trunks and other stable surfaces and also are frequently found on camping equipment and firewood. (File photo/U.S. Forest Service and courtesy of

A publication-quality photo is available at

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