Invasive Borer Threatens N.H. Emerald Ash

Agriculture officials in New Hampshire are scrambling to slow the spread of the emerald ash borer (inset), an invasive beetle discovered in Concord last month. Visible signs of the pest include snaking paths where larvae have tunneled into the wood, called "galleries" (pictured), D-shaped exit marks and bark removal where woodpeckers have tried to reach the borer larvae. If left unchecked, experts say the beetle could wipe out ash trees in New Hampshire within 10 years.

State and federal authorities in New Hampshire are searching for a strategy to stop the spread of the emerald ash borer, a small Asian beetle that has destroyed millions of trees nationwide. The invasive species was discovered in Concord for the first time in March, and local officials are racing to survey the extent of the infestation in Merrimack County.

The sighting was the first in the state, and could have serious consequences for more than 25 million ash trees that populate New Hampshire's northern forests and urban areas. The state's timber industry could also be impacted.

Multiple agencies, including the Department of Resources and Economic Development, the Division of Forests and Lands, and the U.S. Department of Agriculture are working to identify infested trees in and around Concord.

"Our goal, really, is only to slow this thing down long enough so that our ash isn't all gone by the time bio[logical] controls take off," Kyle Lombard told the Concord Monitor. Lombard is a forest entomologist with the Division of Forests and Lands and oversees the day-to-day survey operation.

State and local officials are sampling suspect trees throughout the city and near the first detected tree, or "mother tree," on Hall Street in south Concord.

So far, only a handful of trees have tested positive for signs of the beetle, and the infestation appears to be concentrated along the Merrimack River. That's where most of the infested trees have been detected to date, and that's where the air currents and most of the ash are located, according to Lombard.

Borer larvae tunnel under the bark, cutting off the supply of nutrients to the tree and often killing it within five years of infestation. Typically, when the beetle is introduced to a region, its population grows steadily for the first four years and then explodes in year five. Based on the survey so far, the insect appears to have been in Concord for just three or four years, Lombard said.

The beetle likely entered New Hampshire via firewood from one of the 18 other infested states. Though authorities have banned the import of out-of-state firewood since 2011, the age of the current infestation suggests the first specimen was hauled in before that took effect.

For residents with infested trees, there are essentially two options, and neither is ideal – treat the trees with pesticides, or remove them outright. Older trees, however, typically do not absorb less-heavy pesticides administered through the ground. Such trees often require a stronger variant that is expensive and must be applied directly into the trunk by a certified professional, a more expensive and labor-intensive process.

No other state has successfully removed the beetle so far.