MN: MDA trapping program finds record number of gypsy moths in Minnesota

News Date December 22, 2009

ST. PAUL, Minn. – The Minnesota Department of Agriculture (MDA) has announced its gypsy moth monitoring program caught almost 28,000 moths this year – more than twice the previous high of 12,000 moths caught in 2008.  Nearly 99 percent of the moths collected were in traps in northeastern Minnesota’s St. Louis, Lake and Cook Counties.

According to MDA Plant Protection Division Director Geir Friisoe, the reason for the increase in moth numbers remains unclear. 

“We’re probably seeing a combination of natural spread and accidental introduction by people moving infested materials in from states to the east or from Canada,” Friisoe said.  “We’ve conducted several gypsy moth treatments in northeastern Minnesota in recent years, and the evidence shows we’ve had success controlling the population in the areas we’ve treated.  Unfortunately, the moths keep coming.”

Gypsy moths are among the most destructive tree pests in North America, and they are well established from the East Coast to central Wisconsin.  Gypsy moth caterpillars can defoliate large sections of forest, with oak, poplar, birch and willow among their preferred hosts.  MDA monitors for the pests each year by attaching thousands of cardboard box traps to trees or poles around the state.  In early fall, workers remove the traps and count the moths inside.  MDA set 23,693 traps this year, and caught 27,870 moths. 

When MDA finds a large number of moths in an area, it conducts treatments to eliminate the infestation or slow its establishment.  Over the years, MDA has eradicated dozens of infestations on thousands of acres across the state.  Friisoe noted that trapping data indicate the May 2009 eradication treatments in Minnetonka and Richfield were successful in eliminating the populations.  The department also conducted population control treatments in Lake, Cook, Winona and Houston counties to slow the establishment of the pest there.  Those areas are being evaluated to determine the effectiveness of the treatments, with results expected in 2010.

MDA will work with federal, state and local partners to develop treatment plans in response to the latest monitoring results.  As always, residents of affected areas and other interested parties will have the opportunity to review and comment on draft treatment plans before they are finalized.  More information about gypsy moths and MDA’s control efforts can be found online at www.mda.state.mn.us.