The Mountain Press
By CANDICE GRIMM, Staff Writer March 26, 2006
Unlike those non-native ladybugs with a bad habit of invading human homes, the Hemlock Woolly Adelgid (HWA) is less visible and less buggy to people.
But, for the Eastern hemlock trees in Great Smoky Mountains National Park, the non-native HWA is a deadly enemy that literally sucks the life from its hemlock tree hosts by sucking sap from the base of the tree's needles.
A native of Asia, the HWA has already killed 80 percent of the hemlock trees in the Shenandoah National Park of Virginia, and has devastated hemlock forests from Canada to North Carolina.
With a reputation like that, the 2002 discovery of HWA in Great Smoky Mountains National Park set in motion intensive and continuing efforts to get the insect under control before it can do that kind of damage here.
As a part of those efforts, on Thursday, Park biologists and foresters released the first group of a new species of non-native beetles that kill only the HWA.
Laricobius nigrinus is the second species of predator beetle released in the Park. Since 2004, 143,571 Sasajiscymnus tsugae (St) beetles reared by The University of Tennessee have been released in the Smokies. In 2003, St beetles purchased from out of state labs at a cost of $2.50 each were released.
With the May 2005 dedication of The University of Tennessee Lindsay Young Beneficial Insects Laboratory, both species are being reared at the same local facility.
In Thursday's L. nigrinus beetle release, the media was invited to accompany Tom Remaley, the Park's HWA project coordinator, and Kris Johnson, supervisory forester, to Maddron Bald Trailhead to watch the release of the first group of 50 beetles reared at UT.
"The idea is to get them established in some nice old-growth hemlock stands," said Remaley.
He went on to explain that L. nigrinus is native to British Columbia, and, like the St beetle, feeds exclusively on HWA so it cannot live without the presence of HWA. Both beetles have a lifecycle that synchronizes with phases of the HWA lifecycle, with the exception that the St beetle is most active in summer, while L. nigrinus is most active in winter. Year-round predator activity is expected to help get HWA under control.
"These (L. nigrinus) adults lay their egg in the HWA egg sack. When the egg hatches, the larvae come out and feed on the HWA, then drop to the ground and pupate during summer. In early fall, they emerge and start the cycle over," said Remaley.
In addition to the poppyseed-sized predator beetles, foresters are using insecticidal soap sprayed on infested trees to kill the adelgid, and systemic insecticides that are injected into the ground around the trees or directly into the tree.
Biological controls such as predator beetles are the most effective method for fighting the adelgid in large tracts of forested areas like the Smokies.