Hemlock Woolly Adelgid on a hemlock tree branch. Photo by Diane Palmer  More photos

DATE: 3/15/05

CONTACTS: Hugh Conway, (864) 656-5071

Joe Culin, (864) 656-5041

WRITER: Diane Palmer, (864) 656-4741

Clemson scientists raising predators to battle damaging pest of hemlock

CLEMSON – It’s war. No, it’s not the war in Iraq, but the war against an exotic insect, the Hemlock Woolly Adelgid, in a battle to save the Southern hemlocks.

Clemson University scientists are working with the U.S. Forest Service, other states and organizations to eliminate this extremely damaging pest of the hemlock tree by raising legions of predator beetles that eat the adelgid.

This pinhead size adelgid covers itself with a white, fluffy secretion and sucks the sap from the base of the needles of the hemlock. This prevents the tree growth and causes needles to turn grayish-green and drop prematurely. It can take as little as four years for a tree to die after adelgids attack.

The adelgid was accidentally introduced into the Pacific Northwest from Asia in the 1920s. A second infestation occurred on the East Coast in Virginia in the 1950s. They currently infest about half the area where hemlocks grow in the eastern United States. Eighty percent of the hemlocks in Virginia’s Shenandoah National Park are now dead.

These pests are on the move and were first observed in the Chattooga River Watershed in 2001. The damage is not isolated to the forest. Hemlocks are also susceptible in homeowner’s yards, parks and golf courses.

Jackson-Macon Conservation Alliance, National Forest Foundation, Chattooga Conservancy, USDA Forest Service, Department of Natural Resources and South Carolina Parks, Recreation and Tourism have either provided or helped raise funds for the establishment of a predator beetle rearing facility at Clemson.

For Sasajjscymnus tsugae, predator beetle, nicknamed “Sasaji”, the adelgid is the food of choice. The beetle’s life cycle and the ability to survive the winter are in sync with the prey, according to scientists.

A second predator beetle, Laricobus ningrinus – nickname, “Lari” -- is also being reared to be released at a later date. Raising the beetles is a challenge. They have a complicated life cycle and currently are being reared indoors, where the beetles require different temperatures at different life stages.

So far this year, about 4,000 “Sasaji” beetles have been released in Oconee County and 31,000 into the Georgia Chattooga Watershed. More than 100,000 “Sasaji” beetles were released in 2004 in the Chattooga Watershed in South Carolina, Georgia and North Carolina.

Hemlocks live longer than any other native tree in the eastern United States. Individual trees may live to be 800 years old.

Widespread hemlock deaths would have devastating effects on the Southern Appalachian watershed. Loss of tree cover would affect the number of species and types of plants in the area, as well as diminish the cooling effect of the trees on water, jeopardizing temperature-sensitive trout.

The adelgid can be moved easily by wind, birds, deer, squirrels and other animals. They also can be carried by hikers and campers as well as on infested nursery plants.

For more information, contact Hugh Conway, Clemson researcher, at (864) 656-5071 or hconway@clemson.edu.

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