New Emerald Ash Borer Infestation Near Rochester

Minnesota officials have now  confirmed trees in Olmsted County are infested with the destructive emerald ash borer. The state’s Agriculture Department said yesterday that the county now joins Hennepin, Houston, Ramsey and Winona counties in Minnesota and federal quarantine to prevent the infestation from spreading. The quartantine mandates that any ash logs, lumber, chips and tree waste can’t be taken out of the county without a department certificate. Any violators will be subjected to a heavy fine.


The adult Emerald Ash Borers attack the tops of most ash trees while the larvae of the beetle kill ash trees by tunneling into the wood and feeding on the tree’s nutrients. Not all ash trees are subject to infestation and anyone with an ash tree is urged to contact their local county conservation department for listings. It is estimated that Minnesota has approximately one billion ash trees, greater than any other state.

Winona County, near the interchange of Interstate 90 and U.S. Highway 63, is where the closest infestation is to the Olmstead infestation which is indicative that the beetle was moved in firewood or transported by other means. The beetle does not migrate long distances from its host tree, but rather it attacks other nearby suitable ash trees.

There are ways to identify whether the beetle has attacked a tree. The first it to look for a loss of leaves at the very top of a tree. It will look as if the leaves are almost all eaten at the crown of the tree. The second way is to look for borings or holes in the bark shaped like a “D”. This is because the bug is flat on one side. The boring is the beetle having grown from a larvae to a beetle and surfacing to feast on the leaves above.


So far, twelve counties in Iowa have been infested while five have been infested in Minnesota.