Now is the time to strike, said fellow entomologist George Hamilton, of the New Jersey Agricultural Experiment Station at Rutgers University, who studied the insect's habits with Cooper.
Their work last year revealed the best time to attack the brown marmorated stinkbug: the end of August and first half of September, just before it heads indoors.
The Halyomorpha halys - which is native to China, Korea, and Japan - has flourished across the region since it showed up in Allentown about 15 years ago and has spread across several states.
Earlier efforts to eradicate this skunk of the insect world fell short. Exterminators didn't know when to apply insecticide.
"A lot of insects, like ladybird beetles - ladybugs - come into buildings in the fall, after the weather turns cold," said Cooper, author of The Bedbug Handbook and an owner of Cooper Pest Solutions in Lawrenceville.
Not these little stinkers. They're coming in now, necessitating treatment at entry points - attic vents, and door and window frames. Exterminators use pyrethroids, a synthetic insecticide of low toxicity. No organic alternatives are available, the entomologists said.
"We're talking about preventing them from coming into people's homes," Hamilton said.
Once indoors, "warm spells trick them into thinking it's time to go outside, and that's when people see them inside their houses," he said.
The insects are more a nuisance than anything else. They don't bite, but they do "like to get into the folds of things. They get into your clothes, into your shoes and papers," added Cooper. "Every time you turn around, there's another one."
From the study, "we learned when to kill them with insecticide and how to keep them out of structures," Hamilton said.
In warmer months, stinkbugs are drawn to plants, bushes and trees that bear berries or fruits. "They gravitate toward ripening fruit, seedpods, peach and apple trees," Hamilton said.
Homeowners will never secure their properties well enough to prevent all of the unwanted guests. "But you don't have to leave it open to them. Seal up the major entry points, then leave the [insecticide] applications to the professionals," Cooper said.
Barbara McCormack battled the bugs for a few years at her home in Hopewell Township, Mercer County.
"I hate these guys. They're so creepy," said the retired gynecologist, who now lives in Plainsboro, Mercer County.
"They don't bite you, but they're so ugly," she said. "They're like little dragons."
In Yardley, the pests took up residence in the drop ceiling of Jean Torongo's kitchen in 2008.
"There were dozens of them," said Torongo, 80. "They would drop down into the light when they died and you'd see their silhouettes."
She saw their numbers sharply reduced after her home was treated last year, and she expects to see even fewer this year.
"You have a visceral reaction to them, said David McDonough, 58, of Hopewell, who began seeing stinkbugs at his home two years ago.
"They are ugly and bumbling and fly in a slow pattern, so they're easy to catch," McDonough said. "But if you squash them, they stink - like stale perfume."
An exterminator treated McDonough's home last year and reduced the insects by an estimated 75 percent. This year's early treatment is expected to eliminate 90 percent.
"If you wash them down the sink, they crawl back up," McDonough said. "The only way to get rid of them is flush them."
The pests exit on their own in the spring, usually after other overwintering insects.
Large-scale eradication in the future may require introduction of natural enemies from the stinkbugs' native countries, possibly other insects that attack their eggs, Hamilton said.
"The U.S. Department of Agriculture is looking at other options and may import something from Asia," he said.
In the meantime, stinkbugs are "spreading in an unrestricted fashion, expanding quite a bit geographically," Cooper said. "Our calls [about them] have gone up 50 percent over the past few years.
Stinkbugs have been found in Maryland; Virginia; Delaware; West Virginia; Tennessee; Ohio; New Hampshire; Long Island, N.Y.; Los Angeles; and Portland, Ore.
In these parts, "the heat may have had something to do with it," Hamilton said. "The hotter it is, the faster they develop."
In Pennsylvania and New Jersey, "it's going to be heavy this year," Cooper said. "This is going to be big news in three weeks."
Contact staff writer Edward Colimore at 856-779-3833 or firstname.lastname@example.org.