Beetle from Pacific Northwest may save N.C. hemlocks

May. 04, 2014 @ 08:05 PM

Each September, John Worsley’s home on Hines Branch Road deep in the woods of northern Caldwell County used to be flooded with small beetles that swarmed around the trees outside and piled up on high windowsills.

The beetles weren’t a nuisance, they were saviors of his Carolina and Eastern hemlock trees, fighting a parasite that has decimated hemlock populations in the Appalachians: the hemlock woolly adelgid.

The beetles, which Worsley described as orange ladybugs, were most likely Scymnus coniferarum, or the conifer lady beetle, said Dr. Richard McDonald, owner of Symbiont Biological Pest Management Co. of Sugar Grove.

It has been years since Worsley has seen any of the beetles near his home, though, and he can see signs that the adelgid — a type of tiny insect related to aphids — is taking its toll on many trees on his property, including some just out his front door and now are nearly completely bare.

But help may be only a year or two away, depending on the wind.

The hemlock woolly adelgid is an invasive species that made its way to the Eastern U.S. via weeping hemlocks shipped in from Japan for the nursery trade around the turn of the century, according to McDonald, whose business has been fighting against the adelgids in the mountains of northwestern North Carolina for years. With no natural predators, the pests ravaged the hemlock population unchecked, in some areas killing more than 80 percent of the native hemlocks, which are important to the health of streams and associated wildlife, including trout, crayfish, wood thrush and more.

McDonald is one of the leading entomologists fighting the adelgid, and in 2006, when it was discovered that the hemlock woolly adelgid has long been in the Pacific Northwest, McDonald led a team to Seattle to discover how the pest had not decimated the populations of hemlock there.

What he found was a native predator, the Laricobius Nigrinus, a small, black beetle.

Having a native predator offers a number of benefits, McDonald said, including being much less expensive and being exempt from a slew of permits and certifications from three levels of government.

“I can spend one-fiftieth the money and have 10 times the result,” he said. “Really in some ways it’s a no-brainer.”

The board of directors of the Grandfather Golf and Country Club gave McDonald the funds he needed to make his first trip to Seattle to collect beetles, bringing them back to the golf course to release on the hemlocks there.

“We didn’t have money, so we cold-called on the wealthiest resort in the High Country,” McDonald said.

Since then, he has made more than 50 trips to the Pacific Northwest, gathering beetles and bringing them back to be released in the mountains of Western North Carolina, and he said it’s working.

The beetle colonies spread at a rate of two miles per year or more, and strong winds can carry them farther, McDonald said. After numerous releases at Grandfather Golf and Country Club, the beetles have migrated 30 miles in every direction, and McDonald has spotted them as far away as Blowing Rock, just a few miles from Worsley’s property.

The population of beetles is so strong in the area that more than 60,000 beetles have now been gathered from the Banner Elk area to be spread in other states, especially significant since a release of beetles is usually around 300-500 insects, McDonald said.

“It’s a game of numbers and time,” McDonald said. “We started scrounging way back when and never gave up. That’s why everybody looks to us now.”

Within three years, McDonald said, the entirety of the North Carolina mountains could have a stable population of predator beetles keeping the adelgid in check.

“We have a mature program—it took us 10 years to do it—but we’re ready to supply the rest of the East Coast with beetles,” he said.