South Dakotans ash trees are at risk.
"What we did was cut all the elm out and plant ash trees," said John Ball, an Extension forest health specialist at South Dakota State University. "We couldn't have foreseen the emerald ash borer."
The emerald ash borer is an insect that has killed 15 million ash trees since its discovery in 2002.
It's been found in Michigan, Ohio, Indiana and Canada.
It is spread primarily through firewood containing the insects. To prevent the pest from spreading into the state, South Dakota now bans entry of all out-of-state firewood.
The ash borer can be controlled with pesticide, but spraying is very expensive.
In addition, the trees must be sprayed every year for protection.Associated Press via The Argus Leader
