Ash Borers, Frozen To Death, Likely To Recover
Emerald Ash Borer Spreads in Six More Counties

Ash Borers, Frozen To Death, Likely To RecoverST. PAUL, MN - Emerald Ash Borers, which have been spreading destruction to millions of trees in the Eastern U.S. and Canada, are being dealt a setback by the extreme cold at the northern edges of their invasion. But the cold is likely to slow, not eradicate, the pests.

Emerald ash borer, Agrilus planipennis Fairmaire was detected in North America initially in 2002.

Ash Borers have now infested areas in Michigan, Connecticut, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Maryland, Massachusetts, Minnesota, Missouri, New York, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, Wisconsin, Ontario and Quebec.

It was detected for the first time in Wisconsin in 2008 and in Minnesota in 2009. The insect is now poised to move into some of the coldest regions of North America, especially northern Wisconsin, northern Minnesota, and North Dakota.

Ash Borers, Frozen To Death, Likely To RecoverIn a study by the U.S. Department of Agriculture Forest Service Northern Research Station in St. Paul, MN,  the cold hardiness of emerald ash borer larvae, the overwintering stage of the insect, was found to have a lower limit. Conducted a study between October and December 2013, the study found that larvae collected from naturally infested trees in St. Paul, MN would die when temperatures hit -25°C (-13°F).

In naturally infested logs held outdoors at -28°C at one site, 40% of the larvae died. In a colder area, with temperatures of -34°, approximately 90% of larvae died.

"Overwintering mortality may help to minimize the damage caused by emerald ash borer in areas with extremely cold winter climates," conclude researchers Robert C. Venette of the USDA and Mark Abrahamson of the Minnesota Department of Agriculture in the study (download a PDF).

Have something to say? Share your thoughts with us in the comments below.