AUGUSTA — Gov. John Baldacci has signed into law a bill barring importation of firewood into Maine from other states.

The purpose of the ban is to protect Maine’s hardwood trees from the spread of the Asian longhorned beetle and the emerald ash borer. Destruction of trees by those insects could hurt wood-products industries that employ thousands of Mainers.

The bill’s sponsor, Democratic Rep. Jeff McCabe of Skowhegan, says the problem insect has been found in neighboring states and across the country. Baldacci signed the bill Thursday.

As amended, the bill does not include wood chips, wood pellets, fuel for biomass boilers, pulpwood or other wood sold or transported for manufacturing purposes.