Ravenous gypsy moths return

BY CARLOS SANTOS
Media General News Service
Published: July 30, 2008

CHARLOTTESVILLE — The ravenous gypsy moth is back.
The pest has defoliated 112,340 acres of Virginia’s forests this year, which is more than the combined acreage defoliated from 2004 through 2007.
Virginia Department of Forestry officials attribute the moth’s comeback to some very dry springs that killed off a fungus that feeds on the moth in its caterpillar stage.

“We’ve had two dry springs in a row,“ in 2006 and 2007, said Chris Asaro, the Virginia Department of Forestry Forest Health Specialist.

Wet spring weather fosters the fungus. Asaro said this year’s wet spring, combined with another wet spring next year, should make the gypsy moth population crash again. That didn’t occur this year because the caterpillars are killed by the fungus only when they are nearly full grown and most of the defoliation is done.

“On the other hand, dead caterpillars mean fewer adult moths will be around this summer to lay eggs,“ Asaro said. “So, next year’s defoliation could be considerably lower.“ Officials will know more this fall when they conduct a gypsy moth egg mass survey.

Most of the damage is done because the pests eat leaves in the caterpillar stage, which is ending now as they turn into moths.

Nearly 70,000 acres of defoliation cut across the George Washington-Jefferson National Forest close to the West Virginia state line. An additional 11,750 acres affected Shenandoah National Park, officials said.

The most heavily affected area was in the national forest in Augusta County and southern Rockingham County, which had almost 43,000 acres of heavy defoliation. That area covers about 30 square miles. Heavy defoliation strips most of the leaves from a tree, which then is weakened. Successive defoliation will kill trees.

Another heavily affected area was northwestern Giles County, where more than 15,000 acres of forest sustained defoliation, most in the Jefferson National Forest.

Asaro said oak trees — which the gypsy moth prefers to eat — are slowly being replaced by tulip poplars and maples, which are more resistant to the pest.

The state’s oak tree population is aging anyway and entering a state of decline.

“The gypsy moth is just speeding up the process,“ Asaro said. “The forest is going to be different over time.“

Gypsy moths were introduced into the United States in Massachusetts in 1869 and have been slowly spreading southward ever since. The first defoliation in Northern Virginia was recorded in 1984.

Carlos Santos is a staff writer for the Richmond Times-Dispatch.