COLUMBUS, Ohio — Urban dwellers across the Midwest are having fits this time of year. The ever-increasing invasion of the pesky stink bug is making its way into small crevasses of homes everywhere.

But it’s the farmers’ fields these bugs prefer. According to those at the Journal of Integrated Pest Management, stink bugs were first found in the United States in 1996. They originated in Asia, and there are more than 50 species of stink bugs identified in the Midwest, with the brown marmorated garnering the most attention.

Ohio State University agronomists say since 2012 the brown marmorated has been regularly found in Ohio, Indiana and Illinois soybean fields, creating much economic loss. OSU entomology associate professor Andy Michel is leading research into the species of stink bugs that prey on soybeans: green, brown, red-shouldered and of course, the brown marmorated.

Michel is on the second year of a three-year project funded by the Ohio Soybean Council and the North Central Soybean Research Program to determine what species of stink bugs cause the most damage to soybeans and how prevalent the bugs should be before spraying.

“These bugs pierce through the pod with their wide and sharp mouths, go on to the seed, then add enzymes and saliva to suck up the nutrients,” he explained.

“In the end, it looks like a shriveled-up, brown, discolored seed.

“Oftentimes this damage is not apparent until harvest, because the pod usually retains its shape, despite the smaller seed. That makes it important to scout early for stink bugs and control them if necessary.”

Michel said drought conditions encourage the spread of stink bugs, so unusually dry summers – like those of 2012 and 2016 – saw some of the state’s worst infestations.

He observed a few fields which suffered a 30 percent yield loss in 2012.

Celeste Welty, an OSU extension entomologist, is involved in a 15-state study to determine the best and, ideally natural, way to get rid of the marmorated stink bug. “The stink bug is a terrible pest in agricultural crops, and we want to know how to control them with more sustainable methods than just spraying a lot,” she noted.

Welty said the marmorated stink bugs have a natural predator: The tiny Trissolcus japonicas wasp. It is native of China and was first detected in the U.S. in 2014. It has been found in eight states but not yet in Ohio.

Nowhere in the U.S. is it plentiful, she explained, at least not plentiful enough to keep down the stink bug’s population.

“The wasp appears to be spreading on its own, but it’s so early on in the introduction of the wasp that we really don’t know.”

The studies continue, but the obvious remedy to most growers is spraying – but not so fast, these researchers say.

“Just because you have stink bugs in the field doesn’t mean you need to spray,” Michel said. “That’s because stink bugs could develop a resistance to pesticides, some stink bugs don’t cause as much harm to soybeans as others and some species are actually beneficial, being natural enemies of other soybean pests.

“We want growers to be able to identify stink bug species and determine when their field is at risk for economic damage, and therefore when they should start spraying.”

Robert Koch, research author and assistant professor of entomology at the University of Minnesota, said farmers should start scouting early in corn and soybean fields.

“With corn, farmers should get out in the field the first two weeks after corn emerges,” he said. “Farmers should check at least 10 consecutive plants in five or more locations per field for stink bug injury and stink bugs. Examine the entire corn plant from near the base to within the whorl.

“For corn less than 2 feet tall, consider treatment if stink bugs are present on 10 percent or more of the plant. When injured plants are observed, consider treatment when 5 percent of the plants exhibit injury and stink bugs are present.”

With soybeans, he said, farmers should scout for stink bugs as soon as pods begin to develop, and continue through seed development. Producers should scout for the bugs by using a sweep net or a drop cloth. Farmers with 30-inch spacing or narrower should use a sweep net and those with wide-row spacing should use the drop cloth method to scout.

“All producers should regularly scout the fields in susceptible growth states to determine if the threshold of the stink bug is enough to warrant the use of insecticides,” Koch said.