The long-expected pest was found this week in a tree in St. Paul's Hampden Park community, The Star Tribune of Minnesota reported Friday.
"It's obviously bad news," said Mike Schommer, a spokesman for the Minnesota Department of Agriculture.
Minnesota has 900 million ash trees. Many of the ash trees were planted to replace trees killed by Dutch elm disease.
State officials are expected to ban the movement of any part of an ash tree in or out of Ramsey and Hennepin counties in the Twin Cities area. A similar ban is in place in Houston County because an ash borer was found last month in Wisconsin, about 20 miles east east of the county, the Star Tribune reported.
The pest, native to China and Korea, has killed millions of ash trees in at least 10 states in the last decade.