The Indiana Department of Natural Resources says it’s using chemical treatments to protect large ash trees in areas of Indiana so far unaffected by the emerald ash borer.

Those trees are in western Indiana’s Turkey Run State Park and several nature preserves.

The DNR says the insect invader has killed nearly all mature ash trees across Indiana’s northern two-thirds.

The borer is advancing south and the DNR says all of Indiana’s ash trees will likely die without intervention.

The agency says saving female ash trees could provide seeds for efforts to breed ash trees resistant to the insect that’s killed millions of trees in 30 states.