SPRINGFIELD, Ill. (AP) — The state Agriculture Department says a beetle that's killed hundreds of millions of U.S. ash trees has spread to more Illinois counties.

The agency said Monday that the emerald ash borer is confirmed in 14 new counties, bringing to 50 the number with confirmed infestations.

Eight of those counties already were in a 49-county quarantine zone established to help prevent the beetle's spread — Coles, Douglas, Ford, Marshall, Piatt, Shelby, Warren and Woodford.

Five counties are outside of the quarantine area but now will be added: Logan, Menard, Perry, Sangamon and Williamson.

Peoria and Tazewell counties also will be quarantined after beetles were discovered earlier this year.

The quarantine forbids the removal of ash trees, including firewood.

The beetle's larvae burrow into ash bark, eventually killing the trees through starvation.