Many Minnesotans hoped that last winter’s polar vortex and the nasty cold temperatures it brought with it would push back the Emerald Ash Borer (EAB), which is slowly advancing into the state. According to a U.S. Forestry Service study released last winter, EAB larvae start to die when temperatures within trees reach -20 degrees F. Significant deaths will result when the temps hit -30 F. Certainly, large sections of Minnesota hit the -20 mark — although it is important to remember that the temps must be within the tree and trees don’t care about windchill.
Despite that, there have been some additional infestations of emerald ash borer discovered during the past year. The most recent — and in some ways, most disturbing — was near Rochester in Olmstead County. The infestation is just off of Interstate 90, which has led some experts to conclude that it was the result of wood from an infested area being moved to Rochester. EAB spreads slowly on its own, but when it hitches a ride with humans moving firewood, it really can travel. That’s one reason the Minnesota Department of Natural Resources, the Minnesota Department of Agriculture, the University of Minnesota Extension Service and others who deal with EAB strongly urge that those who burn wood for heat should purchase or cut their wood locally. The five Minnesota counties in which emerald ash borer has been found (Hennepin, Ramsey, Houston, Winona and Olmstead) are under quarantine, meaning wood cannot be moved into or out of those counties.
There’s lots of great information online about spotting a potential EAB infestation. Two things are frequent early signs: general dieback from the top of the tree and an increase in woodpecker action around the tree. Woodpeckers love to eat the larvae and so they will be attracted to potentially infested trees. Of course, you should know which trees on your property are ash trees. The borer only infests ash trees.
Because of the potential for the emerald ash borer to spread, several agencies are planning workshops to help people learn more about the borer and how to identify it. Two workshops will be held in the Rochester area this fall to train more volunteers in that area. You do not have to become a pest detector to attend the events.