2018 Update: Brown Marmorated Stink Bug in Wisconsin

One of the most concerning invasive insects to appear in Wisconsin in the last decade is the brown marmorated stink bug (Halyomorpha halys).  This Asian species delivers a double-whammy of not only damaging crops and other plants, but also being a significant nuisance when it sneaks into buildings in the fall. Since its initial detection in the state in 2010, populations of this insect have built up slowly but steadily. 

Brown marmorated stink bug adult on the side of a building in fall. This is becoming a common site in some parts of the Midwest. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab.

What’s the current status of BMSB in Wisconsin?

As of late 2018, 27 counties have confirmed reports of the brown marmorated stink bug and a handful of other countries have suspected sightings.  This insect has a strong foothold in the state and was confirmed in seven new counties in 2018 alone—Eau Claire, Jackson, La Crosse, Marquette, Monroe, Richland, and Trempealeau counties. 

Distribution of the brown marmorated stink bug in Wisconsin as of late 2018. BMSB has been confirmed in 27 counties. Map Credit: PJ Liesch, UW Insect Diagnostic Lab.

Two core areas currently stand out for brown marmorated stink bug activity in Wisconsin: the Highway 41 corridor from Fond du Lac up to Green Bay and southern Wisconsin from Dane and Rock Counties east to the Milwaukee metro area.  These two areas have the longest history of BMSB in the state and account for the majority of reports thus far. 

Much of the state has yet to encounter this insect or truly experience its impacts.  When the brown marmorated stink bug is first detected in an area, there’s a proverbial “calm before the storm”.   The pattern observed in the state thus far has been a few “quiet” years where low initial populations of this insect result in only a few sightings annually.  However, after a few years in a given area, BMSB populations build up to the point where nuisance problems around structures are noted and reports of potential plant damage begin to trickle in.

What’s the Outlook for BMSB?

Unfortunately, Wisconsin has yet to see the full impact of this invasive insect.  Observations over the last few years have found that BMSB is able to survive our winters and reproduce in the state, so this adaptable pest will most likely continue to build its numbers in the coming years. 

Over time, the brown marmorated stink bug is likely to emerge as one of the top structure-invading pests in the state alongside the likes of boxelder bugs and multicolored Asian lady beetles.  In the eastern US, where BMSB has been established for over a decade in spots, problems can be significant.  In some cases these malodorous insects have been documented invading homes by the tens of thousands

Several brown marmorated stink bug juveniles on a dogwood shrub. Ornamental trees/shrubs, vegetables, and fruit crops can all be attacked by this insect. Photo Credit: PJ Liesch, UW Insect Diagnostic Lab.

While widespread crop damage has not yet been observed in Wisconsin, it may only be a matter of time as population of this insect continue to build in the state.  Agricultural problems have also been significant in the eastern US, giving us a glimpse into what could potentially happen in coming years.  For example, brown marmorated stink bug caused $37 million dollars in losses to apples in the mid-Atlantic states in 2010 alone.  

Having been detected in Portage County in 2017, brown marmorated stink bug may soon start to pose a threat to vegetable production in central Wisconsin.  Similarly, specimens confirmed from Door County in 2017 are forcing fruit growers in that part of the state to keep a close watch on their orchards and vineyards.  With the recent detection of BMSB in several western Wisconsin counties, we’ll likely see BMSB populations slowly build in that part of the state over the next few years as well. 

What should you do?