Maybe now, they’ll come over. Entomologists say the population of this invasive species from Asia appears to have cratered in the Mid-Atlantic. Hurricane Irene and Tropical Storm Lee caused flooding, drowning stink bugs and snuffing out nymphs before they could develop.
But there is also bad news. The bugs have marched to the Deep South. Recently they were detected in South Carolina, Georgia and Florida, where farmers grow juicy vegetable and citrus crops the bugs are known to destroy.
It gets worse. Another type of Asian stink bug has established itself in Georgia. It eats invasive Asian kudzu, a good thing. But the kudzu bug also eats soybeans and other lucrative Georgia legumes.
On a working trip to Atlanta last week, Inkley, a senior scientist for the National Wildlife Federation, saw them flying about, attaching to walls by the hundreds.
“Here we go again,” he said.
Stink bugs come in a wide variety. Many are native to the United States, where prey insects keep them in check. Brown marmorated stink bugs native to China were first discovered in Allentown, Pa., in 1998, likely after crawling out of a cargo ship.
Pennsylvania, West Virginia and Maryland, especially where Inkley lives, were particularly hard hit, for reasons entomologists have not figured out.
So far, the pest has been detected or established in the District and 36 states, a dozen more than last year. Detected means that they’ve been observed and confirmed through lab testing, as opposed to established, which means that they have slipped into homes by the hundreds and ravaged food crops by the thousands.
In the Mid-Atlantic region, where brown marmorated stink bugs are well established, they caused an estimated $37 million in damage in apple crops alone in 2010, the most recent year for which data are available. Some farmers in Maryland said they ruined a third of their peach crop and half of their raspberries last year.
That’s nothing compared with what the warmth-loving bug might do in the Sunshine State, said Douglas G. Luster, research leader for the U.S. Department of Agriculture’s Agricultural Research Service. “It could be like the atomic bomb going off,” he said in an interview last year, implying that the population might explode.
“There is great fear that if the brown marmorated stink bug gets established in Florida, it will do a lot of damage,” Denise Feiber, a spokeswoman for the Florida Department of Agriculture and Consumer Services, said Thursday.
Florida is testing a non-stinging parasitic wasp from Asia, a natural stink bug predator that entomologists might unleash in October, if necessary, Feiber said. The USDA Agricultural Research Center has tested for more than a year a similar wasp that preys on stink bug eggs but has delayed its release for fear that it, too, could become an invasive pest.
The so-called kudzu bug was first spotted in Georgia in 2009. Back then, state entomologists had to search kudzu patches repeatedly for a sign of the insect. But as female bugs lay eggs, with no natural predator, the population exploded in two years, making them easy to sweep into butterfly nets by the thousands. Kudzu bugs are now established in 143 Georgia counties, 42 counties in North Carolina and five in Alabama, according to the University of Georgia’s College of Agricultural and Environmental Sciences.
For a while, they appeared to be a kind of welcome pest. Kudzu bugs, from Japan, chomped on Asian kudzu, reducing growth of the vine by up to 50 percent, said Dan Suiter, an associate professor of entomology at the University of Georgia.
But as it turned out, the bug had a taste for other legumes, such as soybeans. It migrates from kudzu in spring to soybean in July, reducing yields by about 20 percent for two years and costing farmers millions of dollars.
On top of that, the bugs are really annoying. “They’re a general nuisance,” Suiter said. “I was just driving home yesterday and had one in my vehicle. They fly very well. We’ve found it on the 40th floor of high rises. When we first found it in 2009, they covered 2,500 square miles in the area. Their known distribution as of last fall is 108,000 square miles.”
With kudzu bugs limited for now to a smaller area, brown marmorated stink bugs, which, like kudzu bugs, give off a foul bittersweet odor like rotten cilantro when threatened, get the lion’s share of attention from entomologists.
Tracy Leskey, a research entomologist for the U.S. Department of Agriculture, said entomologists can’t stop stink bugs, but they can slow them down. The USDA research program and its academic partners received a $5.7 million grant, allowing them to watch the bugs’ every move.
So far they’ve learned that males emit a scent that attracts both sexes, a possible signal that they’ve found food or they want to mate. Entomologist want to use that to trap them, or “attract and kill,” as she put it.
Entomologists have found stink bugs in woods, in dead trees, under vegetation, “dispersed across the landscape,” Leskey said. “We have to think about a landscape-level solution.”
Hurricane Irene and Tropical Storm Lee weren’t what she had in mind, but they turned out to be a landscape solution. “There appears to be a reduction in the late-season population,” Leskey said.
Inkley, who vacuums the bugs up and collects them for science, counted only 3,000 in his attic this year, enough to make most people’s skin crawl. “I feel like I’m living in heaven, relatively speaking,” he said.
But with a mild winter blending into spring, stink bugs are returning. On a recent warm night, Inkley said he felt tiny legs crawling on his back. He knew right away what was up.
“Any warm day, they come crawling out,” he said.