Experts agreed it was only a matter of time before the emerald ash borer reached Winona.
On Friday, city officials announced that the devastating beetle had been found inside the city limits.
City of Winona director of public works Keith Nelson said an ash borer-infested tree had been confirmed in the Valley Oaks subdivision in south Winona, after the owners of the property had called it in to the city. Nelson said it’s so far the only infestation confirmed in the city; the Minnesota Department of Agriculture is now looking for others in the area.
The city hasn’t exactly been sitting on its hands waiting for the discovery. The Winona City Council approved an ash borer management plan in 2012, calling for the city to treat about a third of the publicly owned ash trees while removing the others and replacing them with different varieties.
“We were fully confident the ash borer would be coming here,” Nelson said. “We’ve been trying to make it as gradual a process as we can, to gradually change the tree canopy.”
The city has treated about 930 trees with physical applications of insecticide, which lasts up to three years, Nelson said. About 70 ash trees have been removed, and 100 new trees have been planted. Nelson said the city spent $28,000 planting trees in 2013 and another $50,000 treating ash trees. It has received a $25,000 grant to help with that cost.
Trees on private property are the responsibility of the owner, Nelson said, but the city can help verify an infestation. The city requires property owners to remove infested ash trees.
The city is planning on using a Prairie Island site to burn or grind up infested trees — it did the same during the Dutch elm epidemic decades ago.
Winona County is under a quarantine that bans the removal or movement of firewood in the county. Movement inside the county isn’t banned, but Nelson recommended property owners move infested wood as little as possible in order to slow the spread of the insect.
The emerald ash borerwas discovered in the state in 2009, and infested areas include Houston and Trempealeau counties and the Twin Cities metro region. Ash borer larvae live under the bark of an infested tree and kill the tree by boring through wood under the bark, cutting off circulation.
The tiny insect, native to Asia, has the potential to devastate ash tree populations across the Midwest because there’s no known way to eradicate it. Neonicotinoid insecticides injected into trees can kill or weaken ash borers that try to tunnel into a tree, but have environmental concerns and are a high-cost solution that isn’t feasible for large-scale applications.
The agriculture department is experimenting with varieties of stingless wasps in Houston and Winona counties that feed on or use emerald ash borer as hosts to incubate their young, and has reported some initial success. But officials admit there isn’t enough data to know what the impact could be on the bug’s spread.