CONCORD, N.H. – For nearly 60 years, scientists have watched helplessly as a war of bug vs. hemlock has played out from Georgia to Maine. Now, they’ve got a new weapon in their arsenal — another bug — and say the tide is turning, at least in New England.
The hemlock woolly adelgid, native to Asia, was discovered in Virginia in 1951. Since then, it has spread to suck up the sap of evergreens in at least 16 Eastern states, including in New England, which hasn’t yet lost large numbers of trees.
A beetle that eats the adelgid was found in Idaho and was introduced to forests in Massachusetts, New Hampshire, Vermont, Maine and New York in 2007. Since then, entomologists have determined that the predator, which can withstand cold weather better than its cousins, is doing its job.
“We’re getting ahead of the game, essentially,” said Mike Bohne, a U.S. Forest Service entomologist in Durham, N.H.
Adelgids can weaken and kill a hemlock over several years. Their eggs appear as white, woolly batches on the underside of branch tips. Sections of hemlock forests in the South, such as in the Blue Ridge, Shenandoah and Great Smoky mountains, have been devastated.
It usually takes years to see results, Bohne said, but entomologists found that the number of beetles had increased after just 1½ years in the Finger Lakes of New York, and in a couple of state forests in Massachusetts and in Brattleboro, Vt.
“It’s very exciting in that the beetles are responding to their new environment and eating adelgids,” Bohne said. “It will take some time before we’ll see a huge population, but ultimately, it’s a very, very positive sign.”
The beetle, called Laricobius nigrinus, appears to be more successful at eating the bad bugs in New England than a similar beetle that’s native to Washington state.
Scientists started introducing that beetle to the 16 affected states in 2003, but it has spread significantly only in the warmer South.
Saving the hemlocks, which grow near rivers and streams, is critical to the health of forests and wildlife, entomologists say.