People cutting firewood on some national forest lands before mid-August may be taking mountain pine beetles back to their trees at home, Forest Service officials say.

Most of the firewood removed from the northern end of the Sawtooth National Forest has been killed by the mountain pine beetle, Sawtooth National Recreation Area Forester Ken Britton said.Healthy trees are attacked during the insect's flight period, which normally occurs between mid-July and mid-August, he said.

Beetles are currently under the bark of dying lodgepole pine, which fades to yellow, brown or red. Britton said the beetles are just about mature. Bringing the wood home at that time could spread the adult insects to other trees, including Austrian and Scotch pines.