Ash borer beetle reaches Cook County forests

The pest blamed for the destruction of millions of trees has reached forest preserves in Cook County.

Forest preserve officials are working with experts from the Illinois Department of Agriculture and the U.S. Department of Agriculture Animal and Plant Health Inspection Service plan to monitor for the small green beetle.

The ash borer's larvae feed on the bark of ash trees. That means the tree can't get its water and nutrients as easily. Infested trees usually die in three to five years.

The insect was first found in Michigan about six years ago and is responsible for the loss of tens of millions of ash trees.

At least 21 counties in the north and central part of Illinois are under an emerald ash borer quarantine.