Gypsy moths gain foothold in northeastern Minnesota
Northeastern Minnesota is the central battleground this year in the state's war against tree-eating gypsy moths.
"We're seeing a big increase in the number of moths caught in our monitoring traps," Minnesota Department of Agriculture spokesman Michael Schommer said. "That's a concern. We are seeing an increase in the infestation in Minnesota, particularly in the northeastern corner of Minnesota."
In response, the state will treat more than 100,000 acres this year, compared to 71,500 acres in the area last year. The state is holding several open houses next week to discuss treatment plans.
"We have upped our acreage," said Lucia Hunt, the state's gypsy moth unit supervisor. "We have to move our treatment areas according to our analysis of the moth population. This year they are more inland and more widespread than ever before."
"Things are getting a little bit closer to the city of Duluth this year."
Gypsy moths, originally invading from Europe, have been moving west across the U.S. for more than 100 years. Their westernmost front now splits Wisconsin, but because the moths can hitchhike on vehicles, they already have moved into pockets ahead of the front, including along Lake Superior's North Shore.
Last year's state trapping program caught more than 27,000 moths -- twice the number found in 2008 -- and nearly 99 percent of the moths were from the Northland. High numbers were found near Clover Valley School in St. Louis County, and Cramer and Finland in Lake County.
"Our treatments are following and responding to these increased, elevated populations of moths," Hunt said. "The whole idea is to slow down the westward progression."
Over 30 years the Agriculture Department has treated more than 65 infestations of the invasive moth across the state. The state uses two methods to control gypsy moths. One is to spray a chemical that confuses male moths so they are unable to find and mate with females. The other uses Btk, a naturally occurring insecticide that attacks the moth in its larval stage.
"Btk is used on areas with a high level of infestation," Schommer said, including locations in the Minnesota cities of Minnetonka and Richfield last year.
The state plans to use mating disruption on nearly 99,000 acres in two treatment blocks and Btk on 2,167 acres in three treatment blocks in Northeastern Minnesota this year. Last year, the state used Btk on approximately 700 acres in the region.
Gypsy moth caterpillars can defoliate large sections of forest, with oak, poplar, birch and willow among their preferred hosts. Because they have little or no natural enemies when they move into an area, they can hit some forests hard, especially forests already stressed by bugs or drought.