Gypsy moths
A recent survey by the Minnesota Department of Agriculture (MDA) found that an isolated population of gypsy moths has become established in Minnetonka. Ranked as one of America’s single most destructive pest of trees and shrubs, this infestation is a threat to trees on both private and public land in Minnetonka.
In September 2008, MDA conducted a survey looking for egg masses—telltale signs of a self-sustaining gypsy moth infestation. The goal of the survey was to determine if there is a viable gypsy moth population and if additional management efforts are needed. Conducted by MDA in cooperation with the U.S. Department of Agriculture and the city of Minnetonka, the survey targeted Minnetonka due to a high number of male moths detected in previous general statewide survey efforts.
The effort turned up several egg masses, and based on this finding, the Minnesota Department of Agriculture will be working closely with the residents as well as city and federal cooperators in the next several months on management efforts to eradicate this population of gypsy moths before they can spread.
Gypsy moths were introduced to America from Europe in the 1860s in an attempt to breed a hardier silk worm. Instead, the caterpillars escaped and headed for the trees with disastrous effects. Their ability to feed and survive on more than 300 trees and woody plant species makes the moths at home in North America as they slowly spread westward in recent decades. Gypsy moth populations are currently established from Wisconsin to the east coast.
People often unknowingly transport this pest to new areas. Gypsy moth egg masses are usually deposited on trees, houses or any outdoor household gear. 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 three square feet of foliage in its lifetime.
Residents should be on the lookout for these buff-colored egg masses, which are about the size of a quarter. If you find an egg mass, immediately call the Minnesota Department of Agriculture’s Arrest the Pest Hotline at 651.201.MOTH (6684).
Learn more viewing this gypsy moth brochure or these gypsy moth fast facts.
Gypsy moth survey conducted in December, 2007
On Monday, December 10, 2007, four agencies joined together to conduct a gypsy moth survey in the city. There were representatives from the lead agency, the Minnesota Department of Agriculture as well as the US Department of Agriculture, Minnesota Department of Natural Resources and the City of Minnetonka. This time of year, surveyors look for quarter-sized fuzzy yellow egg masses under eaves and decks, in fences, on tree trunks, and under firewood piles.
The gypsy moth is a non-native insect that feeds on the leaves of over 300 species of trees and shrubs. The gypsy moth caterpillar is the one that does the damage: they rapidly eat the leaves of trees and shrubs from early spring until July. This stresses tree and can kill it. The moths thrive in many habitats because they feed on so many species and have few natural enemies here. Some of their favorite trees are oak, birch, apple, boxelder, poplar, and willow.
The MN Department of Agriculture (MDA) has had a gypsy moth monitoring program since 1973, with traps set to detect the insect throughout the state. Typically there are 1–3 moths found in a trap, but this summer, they found up to 8 in some of the traps in Minnetonka. Numbers this high put the city at risk for a permanent infestation.
The good news is that instead of doing a city-wide search, researchers are able to zero in the neighborhoods that contained the highest number of moths in their traps. Monday’s gypsy moth hunt was conducted on 36 acres of private properties, where homeowners were notified a week in advance and invited to join in the search. No egg masses were found, so the MDA will increase the density of the traps next June in the affected region. Traps will remain in place until mid-August to capture the entire male moth flight period. A control program such as spraying cannot occur until egg masses are found which confirms the presence of an established and reproducing population.
The portion of the city that was surveyed is roughly west of 494, north of Excelsior Boulevard, east of Woodhill Road and south of MN Highway 7. This area has several large remnant patches of oak woodland brushland, which is one of seven types of native wooded ecosystems left in the city. Since oak trees are one of gypsy moth’s favorite meals, it is especially important to eradicate this insect before it becomes established.
Homeowners in this region of the city are being asked to learn what gypsy moths look like in all its life stages so they can spot it if it is living in their yards.
Like a butterfly, the gypsy moth has four life stages:
- Egg mass
- larvae (the caterpillar)
- pupa (the cocoon)
- flying moth
The MDA has a hotline set up for residents who have observed the moth: 651.201.6684. The natural resources division is working to educate residents about gypsy moths. Future training for seasonal tree inspectors will incorporate gypsy moth identification. There are no penalties or costs if the moth is found in a residents’ yard. The MDA will handle any treatments, and if it is found on a tree, it need not be cut down.
This isn’t the first time Minnetonka has been a host to gypsy moths—in fact, the city was treated for it in 1990, which seemed to have eradicated the population until now. Neighboring communities have been affected, including Golden Valley and Minneapolis in 2002 and Brooklyn Park in 2006.
Since gypsy moths are not established yet in Minnesota, when high populations of moths are found in traps, eradication programs are implemented. The pest is established as close as eastern Wisconsin, so transport of egg masses on wood, camping equipment, and automobiles is common. Because the moths have been found in a residential area, and not near a lumber mill or nursery, the MDA believes the moth hitch-hiked to Minnetonka by human movement from a quarantined area.
To learn more about the gypsy moth, visit www.mda.state.mn.us/plants/pestmanagement/gypsymoth.htm or call the city forester, Emily Barbeau, at x8421.
