UPDATE: Wet spring kills harmful gypsy moths in Virginia

The cool, wet spring wasn’t just good for replenishing water reserves — it also has killed off vast swaths of gypsy moths that infested mountain forests throughout the state.

Virginia Department of Forestry officials said Tuesday the moths damaged nearly 75 percent fewer acres than last year. They credit the weather for allowing a virus and fungus to flourish and kill off most caterpillars this spring.

The moths, which are an invasive species, voraciously feed on the leaves of hardwood trees, particularly oaks. This year, the moth defoliated — or destroyed the leaves of trees — about 29,000 acres statewide. Last year 112,340 acres were damaged.

Areas in Central Virginia are not currently infested with the moth, mostly because the oak tree density is not as high, said VDF spokesman John Campbell. The majority of the damage, 12,288 acres, occurred across the George Washington and Jefferson National Forests, mostly close to the West Virginia line, officials said. Nearly 7,500 acres in Shenandoah National Park were impacted.

Most significantly, said state forester Bob Boeren, is many trees that were damaged early this spring grew leaves back to nearly normal amounts by early July, something he’s never seen.

In early June, Boeren said he noticed that the caterpillars were dying off. By late June, he saw none alive.

When he flew over the area in mid July, Boeren said what trees had been defoliated were growing new leaves. Ordinarily, once a tree loses leaves it rarely grows them back in the same season, which robs the tree of essential nutrients to stay alive through the winter, “It’s unusual to see that, but because of the wet weather, I guess, the trees were able to produce another set of leaves quicker,” Boeren said.

The only area that saw an increase in acreage defoliated was around Roanoke, particularly around Bent Mountain and Poor Mountain. This year, 5,389 acres were impacted compared to 4,376 acres last year.

“This year, they surfaced in a lot of places I hadn’t seen them before,” Boeren said. However, this year, only 12 counties had defoliated acres, compared to 20 counties in 2008.

Large swaths of Augusta County forest that was defoliated last year was relatively untouched, a state map showed. The most widespread pockets of infestations were in Rappahanock County, western Montgomery County and Giles County, the map showed.

Boeren said during his aerial surveys, he made sure to check the Peaks of Otter, and while he saw some trees without leaves on Sharp Top and other nearby peaks, ground checks showed that gypsy moths were not the culprit.

Gypsy moths, which are native to Europe, Asia and Africa, were introduced in Massachusetts in 1869 and have gradually filtered south since. In 1984, almost 400 acres in Virginia were defoliated for the first time.

National, state and local agencies have worked together for years to control the pest, usually using some type of spray, Campbell said. Several years ago, the population crashed, but has gradually rebounded because of dry and warm springs, he said.

While it’s unlikely that this year’s kill has fully eradicated the pest from state forests, Boeren said he has hope that next year’s impact will be negligible because this year’s crop did not survive long enough to mate and lay eggs.

“We’re keeping our fingers crossed that we won’t have much, if any, defoliation next year.”