Gypsy Moths: Minnetonka’s Got ‘Em

According to the Minnesota Department of Agriculture (MDA), an isolated population of gypsy moths has taken up residence in Minnetonka’s Opus area. Ranked as one of America’s single most destructive pests of trees and shrubs, this infestation is a threat to trees on both private and public land in Minnetonka.

In response, the MDA will be spraying, by plane, a biological insecticide, starting the week of May 23. A second treatment scheduled for 7 to 10 days later. According to the city, the MDA is also working closely with city residents and officials in an effort to eradicate this population of gypsy moths before it can spread. Treatment timing depends on weather conditions and gypsy moth development. Area businesses and residents have been notified of this spring application.

Minnetonka was successfully treated for gypsy moths in 1990. But neighboring communities have found gypsy moths in the last ten years. Golden Valley and Minneapolis were treated in 2002, Edina in 2004 and Brooklyn Park in 2006. Portions of Minnetonka were also spray-treated in 2007 and in 2009.

The gypsy moth is a non-native insect that has been destroying and threatening woodlands in the United States since being introduced to America from Europe in the 1869, when they were brought here in an attempt to breed a hardier silk worm. The gypsy moth caterpillar does its damage by feeding on the leaves of over 300 species of trees and shrubs. Their feeding takes place from early spring until July and can stress, defoliate and kill trees. Very few natural enemies and a seemingly endless array of hosts make the gypsy moth one of the most dangerous pests in the country.

In 1912, the USDA declared gypsy moths a federally regulated pest and has since quarantined all or parts of 19 states. The MN Department of Agriculture has had a gypsy moth monitoring program since 1973, with traps set to detect the insect throughout the state.

Each summer, the MDA completes a trapping program that targets male gypsy moths. The traps are baited with a pheromone that mimics female gypsy moths, which cannot fly. When higher numbers of the males are found, a survey is conducted the following winter to search for egg masses, which would indicate a reproducing population of gypsy moths. If egg masses are confirmed in the survey, the MDA plans a control treatment in the spring to eradicate the gypsy moth in its caterpillar stage.

Gypsy moth populations are currently established from Wisconsin to the east coast of the United States. While gypsy moth is not yet an established pest in Minnesota, it has been found here. State officials monitor the gypsy moth population and take actions to eradicate it when moths are detected. Treatments that target the gypsy moth in its caterpillar stage have been effective in suppressing its further spread and establishment.

Gypsy moths spread most often as “hitchhikers.” Transport of egg masses on firewood, camping equipment, and automobiles is common. Individual egg masses can contain between 500 and 1,000 moth eggs. These eggs hatch into caterpillars in the spring, and each caterpillar can eat up to 11 square feet of foliage in its lifetime

That’s why officials ask locals not to move firewood and to check vehicles and equipment before leaving a gypsy moth infested area, such as eastern Wisconsin.

Residents should also be on the lookout for buff-colored fuzzy egg masses, which are about the size of a quarter, especially under eaves and decks, in fences, on tree trunks and under firewood piles.

The MDA is the lead agency for the control of gypsy moth, with support and cooperation also coming from the US Department of Agriculture, US Forest Service and the Animal and Plant Health Inspection Service. If you think you have seen a gypsy moth, call the MDA’s Arrest the Pest hotline: 651.201.MOTH (6684). To learn more about gypsy moth, click here. 

*Information provided by the city of Minnetonka