Bitter winter has impact on gypsy moth in Minnesota

Minnesota Department of Ag Logo Last winter’s harsh temperatures have resulted in some positive benefits – a decline in the state’s gypsy moth population. The Minnesota Department of Agriculture (MDA) captured approximately 500 moths this year in traps around the state. That’s a major shift from last year’s count of over 71,000 moths.

“We knew going into this survey season that our numbers would be down,” said Kimberly Thielen Cremers, MDA’s Gypsy Moth Program Supervisor. “Studies have shown extended stretches of extreme cold have an impact on gypsy moth eggs as they overwinter. However, we cannot let our guard down over this invasive insect.”

In fact, University of Minnesota research has shown gypsy moth egg masses can survive a harsh winter if located below the snowline.

“While the decrease in moths is good news, we know they will bounce back quickly.” said Dr. Brian Aukema of the forest insect laboratory at the University of Minnesota. “A single surviving egg mass will produce more than 500 hungry caterpillars.”

The placement of survey traps throughout the state also affected 2014 trapping numbers.

“We placed 60 percent fewer traps in the quarantined counties of Lake and Cook this year,” said Thielen Cremers. “We know a reproducing population is established there; 90 percent of the moths caught in the state in 2013 were in those two counties, so this year we placed more traps ahead of that established population to keep on top of the spreading gypsy moth infestation.”

Gypsy moth caterpillars, which are not native to North America, eat the leaves of many trees and shrubs. Severe, repeated infestations can kill trees, especially when the trees are already stressed by drought or other factors.

A male, gypsy moth caterpillar (photo from www.constructionandtreeservices.com)

A male, gypsy moth caterpillar (photo from www.constructionandtreeservices.com)

Last winter’s harsh temperatures have resulted in some positive benefits – a decline in the state’s gypsy moth population. The Minnesota Department of Agriculture (MDA) captured approximately 500 moths this year in traps around the state. That’s a major shift from last year’s count of over 71,000 moths.

“We knew going into this survey season that our numbers would be down,” said Kimberly Thielen Cremers, MDA’s Gypsy Moth Program Supervisor. “Studies have shown extended stretches of extreme cold have an impact on gypsy moth eggs as they overwinter. However, we cannot let our guard down over this invasive insect.”

In fact, University of Minnesota research has shown gypsy moth egg masses can survive a harsh winter if located below the snowline.

“While the decrease in moths is good news, we know they will bounce back quickly.” said Dr. Brian Aukema of the forest insect laboratory at the University of Minnesota. “A single surviving egg mass will produce more than 500 hungry caterpillars.”

The placement of survey traps throughout the state also affected 2014 trapping numbers.

“We placed 60 percent fewer traps in the quarantined counties of Lake and Cook this year,” said Thielen Cremers. “We know a reproducing population is established there; 90 percent of the moths caught in the state in 2013 were in those two counties, so this year we placed more traps ahead of that established population to keep on top of the spreading gypsy moth infestation.”

An example of tree damage from gypsy moth infestations (photo from gypsymothalert.com)

An example of tree damage from gypsy moth infestations (photo from gypsymothalert.com)

Gypsy moth caterpillars, which are not native to North America, eat the leaves of many trees and shrubs. Severe, repeated infestations can kill trees, especially when the trees are already stressed by drought or other factors.

For more information on gypsy moth, go to www.mda.state.us/gypsymoth.