The Minnesota Department of Agriculture says it's found two emerald ash borer-infested trees in the southeastern Minnesota city of La Crescent.
MDA entomologist Mark Abrahamson said finding the first infested trees is like discovering the tip of an iceberg. He said La Crescent officials should decide within a year on a management plan to treat or destroy infected trees.
"Even though it may take several years to get to the point where it's really bad we don't want to just let it go in the meantime," he said. "Every year we let it go it will get harder to, kind of, pull it back."
Infestations have also recently been found at the Fort Snelling golf course in St Paul, near Nicollet Island in Minneapolis, and in rural southeastern Houston County. Emerald ash borers have killed millions of trees in 18 states.
They are spread by moving infected ash products, like firewood.
La Cresent officials have scheduled a meeting for Jan. 16 to tell residents how ash trees on their property will be effected.