Insects Leading Threat to U.S. Forests

Gypsy moth egg masses

Marauding insects have become a leading threat to the nation's forests over the past decade, a problem made worse by drought and a warming climate, a federal report says.  Bark beetles, engraver beetles and gypsy moths are the primary culprits behind a threefold increase in forestland mortality caused by insect attacks between 2003 and 2007, according to the 2010 National Report on Sustainable Forests.  In recent years, Pennsylvania has seen gypsy moth, hemlock wooly adelgid, and forest tent caterpillar.  Now we are beginning to see emerald ash borer spreading across the state.

2010 National Report
 on Sustainable Forests

The volume of forests in the lower 48 states killed by bugs totaled 37 million acres during the period, up from 12 million during the previous five years. Millions of additional acres have perished since.  Despite the threats, the report says overall U.S. forest acreage has remained stable at about 751 million acres over the past 50 years.