By Kevin Fitzgerald
Since its discovery in Pennsylvania in 1998, the brown marmorated stink bug (Halyomorpha halys), an invasive species native to eastern Asia, has swept into most U.S. states, parts of Canada, and several European countries. The creature feasts on a wide variety of fruits, vegetables, soybeans, and ornamental plants.
New research published in Environmental Entomology in an article called “Occurrence of Brown Marmorated Stink Bug, Halyomorpha halys (Hemiptera: Pentatomidae), on Wild Hosts in Non-Managed Woodlands and Soybean Fields in North Carolina and Virginia” may offer growers some relief, however. Scientists from Virginia, North Carolina, and Georgia have found that these stink bugs prefer certain wild hosts, including tree of heaven, catalpa, yellowwood, paulownia, cherry, walnut, redbud, and grape. This knowledge, according to the authors, should “aid in the search for H. halys in new areas, as well as serve as one predictor of the likelihood of a certain area to attract and sustain large H. halys populations.”
“During the early part of the summer, about now, you have bugs in those trees laying eggs,” said co-author Dr. Thomas Kuhar, assistant professor of entomology at Virginia Tech. “They’re going to hatch and then they’re going to start developing and later on that edge, wherever there are trees, that’s where you’re going to have an invasion of the bug moving onto an agricultural commodity.”
The authors also found that the stink bugs prefer the edges of crop fields, and knowing that may give farmers clues about where and where not to spray pesticides.
“We learned that they don’t move very far,” Kuhar said. “If it’s a big soybean field, you’re only going to find them in the first fifty feet from the edge. We’ve got three years of data showing that growers only need to treat the perimeter of the field. The bugs really don’t move all the way to the center of the field. They like that adjacent wooded area.”
Part of the reason why the stink bugs stay near the edges of fields has to do with food, and part of it has to do with temperatures. Flat fields can be hot, so the insects escape to the shade of the trees.
“It’s good for moving back and forth for food, and they require that shade when you get into the heat of the summer,” Kuhar said. “The bugs can’t tolerate extremely high temperatures. So that’s some other information that we’ve learned, that if you have a day of 100 degrees and you’re in a wide open cotton field, the bugs probably aren’t going to survive that. We’ve tried to put bugs in mesh bags on cotton bolls to see their effect on cotton. We found that experiment challenging because when we did it in Virginia, on days that exceeded 100 degrees, it would kill all the bugs. It’s starting to tell us that the bugs need certain things, temperatures a little bit cooler and a chance to get to shady areas, so that’s why that edge is important. Not to mention that these earlier host plants are these trees. That’s a key finding, especially as this bug moves into other states from the mid-Atlantic states. Spreading out to the south and spreading out to the midwest, you’re going to get different kinds of habitat. The mid-Atlantic states may just be absolutely favorable for it, because we have our Appalachian Mountains and a lot of our agricultural fields are surrounded by woods. Whereas when you get into the Midwest and the Cornbelt, that’s not the case. And when you get into the deep South, all of a sudden it’s hot and we’ve got big open fields. These findings, as the bug moves forward, may show that this may not be so big of a deal in some of these large-acreage commodities that everyone thought, so that’s kind of new.”
That’s good news for farmers in the Midwest and the South, but there may be more. According to Dr. Kuhar, nature may eventually bring the BMSB under control.
“We’re also looking at some of our native natural enemies that are out there, predators that are eating the bugs or parasitoids that are stinging them and developing on them,” he said. “Are some of these native ones starting to recognize brown marmorated now? There’s a little indication that more and more we’re seeing natural predators and parasitoids starting to attack this insect. It’s one of these things that over time indicates that nature may right itself there and come back into balance. It’s a theory, but it’s a theory that’s been proven before. Anything else that’s come over before and that’s been an invasive, in time Mother Nature takes care of itself. There’s not much really we can do to manipulate the system, just let it happen and take note of whether more insects are eating the stink bugs.”
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Kevin Fitzgerald is a freelance science writer living in Connecticut. He has published in newspapers, encyclopedias, and online.