Every fall, residents throughout Wisconsin and many other parts of the country face an invasion by a number of insects: boxelder bugs, multicolored Asian lady beetles, western conifer seed bugs and cluster flies, to name a few. With the coming frosts, these insects are simply trying to find a sheltered location to settle for the winter. Out in nature, many of these insects would simply crawl into a rock pile or beneath the loose bark of a dead tree to overwinter.
But why rough it out in nature if there are perfectly good buildings to sneak in to? Next time you’re cleaning the gutters, take a moment to peek around the outside of your house. Small gaps in siding, soffit areas, around door and window frames, and cracks in the foundation are all potential spots for insects to sneak through. And if they make it through? Well, you could be in for some extended visitors. . .
In addition to the usual fall invaders, a relative newcomer starting to pop up in Wisconsin and other parts of the Midwest is the invasive Brown Marmorated Stink Bug (Halyomorpha halys). Like the boxelder bugs and multicolored Asian lady beetles, brown marmorated stink bugs (BMSB) like to find their way indoors for the winter. This Asian species was first detected in Wisconsin back in 2010 and for reasons we don’t fully understand, their numbers have been quite low the past few years. As of late 2014, BMSB has been confirmed or suspected in 10 Wisconsin counties, with most of the reports coming out of the Madison and Milwaukee area. A handful of sightings each year has been the pattern.
Unfortunately, we may be at the beginning of a shift in BMSB populations in the state. In early 2015, there were at least 6 specimens found in Wisconsin by early March. Despite the quiet summer, the sightings have started popping up again in late September and October of this year. What’s more concerning is that we’re starting to see groups of these insects clustered together (previous sightings had consisted almost exclusively of lone individuals).
Not only are these unwanted houseguests a nuisance, but quite frankly, they smell bad. True to their title of “stink bug”, brown marmorated stink bugs possess glands that can emit a pungent odor. Some consider the odor to be coriander-like, while others say it resembles musty gym socks. Invasive species [check]. Nuisance invader [check]. Smells bad [check]. That’s all, right? Unfortunately, not quite. Just like a bad late-night infomercial: Wait! There’s more!
It turns out that brown marmorated stink bug has the potential to be quite a nasty plant pest and rivals the Japanese beetle in the breadth of its palate. Brown marmorated stink bug seems to feed on just about anything under the sun: field crops like corn and soybeans, vegetables like tomatoes and peppers, and even ornamental trees and shrubs. Fruits like apples and grapes can be hit especially hard. In some cases, the mere presence of BMSB can be a problem: imagine being a vintner and having your batch of wine tainted by the presence of a few squished stink bugs! In the eastern U.S. there are regular reports of agricultural problems and growers have to spray to control these insects. We haven’t had any reports of plant damage in Wisconsin yet, but that could change over time if BMSB populations continue to climb.
So what can you do about brown marmorated stink bugs? For starters, learning to tell them apart from our native stink bugs is relatively easy. Look for the alternating “checkerboard” pattern along the back edge of these half-inch long insects and the two light bands on the otherwise brown antennae.
With relatively few sightings in Wisconsin at this point, we’re still trying to get a feel for where this insect is. If you suspect that there may be brown marmorated stink bugs around your house, take a picture of the insect and email it to me at (firstname.lastname@example.org) for identification. Another option is to collect a physical sample and mail them in to the Insect Diagnostic Lab for identification (instructions on how to submit samples can be found here).
If brown marmorated stink bugs or other fall invading insects are trying to get into your house, one of the best things to do is to inspect the outside of your home and physically seal up cracks and crevices where they’re trying to sneak in. Once fall invaders are indoors, hauling out the hose attachment on the vacuum cleaner is often one of the best steps to remove them.