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Cold Winter Temperatures Set Emerald Ash Borer Back in Minnesota

Photo of Larvae of emerald ash borer on an ash tree from which the bark had been peeled in April 2014. The larvae are dead (dark brown instead of cream), killed during the winter of 2013-14. Robert C. Venette, USDA Forest ServiceLarvae of emerald ash borer on an ash tree from which the bark had been peeled in April 2014. The larvae are dead (dark brown instead of cream), killed during the winter of 2013-14. Robert C. Venette, USDA Forest ServiceSnapshot : Emerald ash borer is the most devastating nonnative insect pest of trees in the United States. Overwintering larvae are unable to survive the winter if temperatures drop too low. During the winter of 2013-14, temperatures were sufficiently cold in portions of the Twin Cities to kill 60 to 70 percent of larvae. Potential mortality of emerald ash borer was described by the media as "the silver lining" of the Polar Vortex.

Principal Investigators(s) :
Venette, Robert C. 
Research Location : Minnesota
Research Station : Northern Research Station (NRS)
Year : 2014
Highlight ID : 645

Summary

Emerald ash borer has devastated urban and natural forests in most states where it occurs, causing 100 percent mortality of susceptible ash species. Although emerald ash borer has been in Minnesota since 2009, little mortality has been observed and spread has been slower than in other states. Forest Service researchers evaluated the role cold temperatures might play in regulating populations of this insect. In general, the insect survives exposure to temperatures from 0 to -20°F by producing cryoprotectants, so in many places, cold temperatures may not have an impact on this insect. However, as within-tree temperatures fall below -20°F, mortality rates begin to increase. With the Polar Vortex in January 2014, air temperature in the Twin Cities fell to -23°F, a temperature that could cause up to 80 percent mortality. Samples taken from cut logs and standing trees that had been outdoors during the winter showed that 60 to 70 percent of larvae had been killed in most locations. Winter mortality of emerald ash borer is unlikely to eliminate this insect but may give natural resource managers more time to respond to this insect in areas where extremely cold winter temperatures (less than -30°F) are common.

Forest Service Partners

External Partners

 
  • Minnesota Environment and Natural Resources Trust Fund
  • Minnesota: Department of Agriculture and Department of Natural Resources
  • University of Minnesota