Emerald ash borers continue to spread across the northern plains, putting ash trees at risk.

Jonathan Larson is an entomologist with the University of Nebraska Extension and says treating as trees depend on how close you are to an active infestation..

Larson says once treatment begins, it has to continue..

Larson says its best to check ash trees every year…

The bug has been reported around Sioux Falls, Sioux City and the Omaha and Lincoln areas.