A stink bug crawls around an apple. (Photo by Katherine Frey/The Washington Post) (Katherine Frey/THE WASHINGTON POST)

For months in the spring and summer, homeowners and farmers alike in Loudoun County braced themselves for the return of the brown marmorated stink bugs – the dreaded insect that invaded houses, fields and orchards last year, dealing a hefty blow to the agricultural community and the sanity of local residents.

Scientists cautioned that the 2011 might be even worse, with the population predicted to peak between August and October.

But there was an unexpected turn of luck: Fall arrived, and the anticipated tidal wave of stink bugs did not.

“We have no idea as to why that is,” said Christopher Bergh, a Virginia Tech associate professor of entomology. “But there does seem to be an emerging consensus that the populations are down compared with last year.”

Last year, stink bugs – which are known to feed on more than 300 types of host plants – inflicted significant damage to crops of apples, peaches, grapes, soybeans and other fruits and vegetables in Loudoun County.

While experts said it was difficult to determine total losses due specifically to stink bugs, they estimated that the mid-Atlantic region suffered roughly $37 million in losses last year solely as a result of stink bug-inflicted damage to apple crops. Organic farmers, who avoid using insecticides that might provide some measure of protection from the insects, were also hit especially hard.

Tyler Wegmeyer, who owns Wegmeyer Farms in Hamilton and is a director of congressional relations for the American Farm Bureau, said local farmers were pleased to see fewer injuries to crops.

“We haven’t had the same numbers of the bugs that we did last year,” he said. “There’s been a little damage, there’s been some, but not the severity of last year. We’re very pleasantly surprised.”

Wegmeyer said he lost 50 percent of his raspberry crop last year to stink bugs – a number that he estimates dropped to around 10 or 15 percent this season. He credits the lower numbers of stink bugs as well as the heightened awareness of local farmers and growers.

“It wasn’t a surprise situation like it was for us last year,” Wegmeyer said. “This was one of the biggest threats that we’ve had in some time. We really spread the word, and people were looking at their crops and taking precautionary measures to make sure they were on top of it.”

Local homeowners also report seeing fewer bugs, Bergh said. Last year, many residents were overwhelmed by the sight of the insects gathering in windows and doorways and crawling across walls and ceilings.

“Fortunately we haven’t encountered the same number of calls from homeowners this year as we did last year,” Bergh said. “It’s a mystery to us at this time.”

Bergh said that members of a brown marmorated stink bug working group — including stakeholders, researchers, and representatives of the Environmental Protection Agency, among others — will gather for a two-day meeting in late November, after the harvest season is over and further data has been collected and analyzed. They will attempt to answer the question of why the stink bug population appeared to drop in 2011, and what factors — environmental and otherwise — might be responsible.

“It will be a comprehensive meeting... we’ll begin to interpret what the data means, and what that tells us about how we should proceed in 2012 and beyond,” Bergh said.