With the passing of the autumnal equinox last week, it’s time to turn our attention to the home invasion of stink bugs that has become a stinky annual tradition throughout much of the country. Brown marmorated stink bugs (BMSB) now occupy 42 states and two Canadian provinces here in North America. In recent years they have also turned up in several European countries including Lichtenstein, Switzerland, France, Italy, Germany and Hungary.
Last week on one of those spectacular autumn afternoons that grace our region, I and other trekkers on Sugarloaf Mountain were greeted by the vanguard of stink bugs cavorting on trees, stones, and buildings near the rocky mountaintop. On warm afternoons last week dozens of stink bugs decorated fruits of a redbud tree in my yard and leered through my window screens.
Why are stink bugs on the move? For the past several weeks, stink bugs have been fattening up on corn, soybeans, garden vegetables, and fruit. But soon this cornucopia of earthly delights will disappear for BMSB and other herbivorous insects. In temperate locations like Maryland, winter halts the growth of deciduous trees and shrubs and withers herbaceous plants. Food for the plant and fruit-eating stink bugs all but disappears. With the arrival of cold weather stink bug movement slows to a crawl and their development grinds to a halt. Prior to this inimical season, stink bugs seek refuge to chill-out where they are protected from harsh weather and dangerous predators.
Why do stink bugs enter homes and man-made structures? Many folks incorrectly believe these home invasions provide warm winter refuge for stink bugs. Bear in mind that millions of years ago when these creatures evolved, there were no mansions or man-made structures to invade. Until recently, the natural winter redoubts of these stinkers were largely unknown. However, a clever study revealed large, freshly deceased but still standing trees are a prime winter hideout for stink bugs in natural settings. The loose bark of these trees affords a fine location for stink bugs to crawl under and escape the ravages of winter. Rocky ridge tops can provide many dead trees and abundant places for stink bugs to chill-out.
For many viewers of Bug of the Week, stink bugs on rocky ridge tops seems like a remote problem. However, the nuisance potential of BMSB is almost without equal. To a stink bug, a home provides a wonderful assortment of overwintering opportunities beneath siding, behind shutters, and in attics. The pending invasion some homeowners face is no trivial matter. In 2011, a homeowner in western Maryland captured more than 26,000 BMSBs from January through June as they moved about his home seeking egress from their overwintering refuge. That’s a lot of nuisance!
While populations of BMSB were lower throughout our region in 2011 and 2012, 2013 was a year of relatively high numbers of stink bugs and an onslaught was expected in 2014. Fortunately, the stink bug tsunami never really arrived and farmers, growers, and gardeners in our region experienced some much needed relief during the summer of 2014. A similar phenomenon was observed in many parts of the invaded range in 2015. The prolonged cool wet spring and early summer witnessed fewer BMSBs in many parts of Maryland. However, record heat in July, August, and September has spiked stink bug numbers along the piedmont in West Virginia and Virginia and many places will have a bumper crop of BMSB this fall.
In the waning days of summer stink bug nymphs fatten-up on delectable vegetables like this tomato.
Why do populations of BMSB fluctuate so dramatically from year to year? Scientists at Virginia Tech and the USDA’s Appalachian Fruit Lab have evidence that visits from polar vortices in the winters of 2014 and 2015 put a beat-down on overwintering BMSB in our region. Fascinating studies at the University of Maryland suggest that our smoking hot summers kill some of the gut microbiota critical to the normal growth and development of stink bug nymphs. Mounting evidence from several universities and government laboratories in our region suggests that indigenous and introduced predators and parasites may be catching up with stink bugs and levying a toll on their populations (see Death of a stink bug, Part 1, Part 2, and Part 3). My money is on the possibility that a suite of factors and events conspired to reduce stink bug numbers in our region.
As we await the autumnal arrival of these home invaders, there is a way you can help scientists better understand how BMSB has affected you and how you have dealt with this stinker. If you click on the following link, you will arrive at a short survey at the world famous StopBMSB website, the premier information source for all things BMSB. By completing the survey you will help us learn where BMSB is, how much of a problem it is to you, and how you are dealing with BMSB. And we promise, the survey is anonymous and you will not receive crazy phone calls, emails, texts, or junk though the mail by completing it. Bug of the Week and StopBMSB thank you in advance.
To complete the BMSB survey, please click here: https://www.surveymonkey.com/r/BMSBsurvey
To learn how to keep BMSB out and what to do when they get in, please watch this video.
Bug of the Week thanks Doo-Hyung Lee, Doug Inkley, Tracy Leskey, Galen Dively, Tom Kuhar, Chris Taylor, Paula Shrewsbury, and other members of the BMSB Working Group for providing information and inspiration for this episode. Interesting studies, including one by D. B. Inkley, “Characteristics of home invasion by the brown marmorated stink bug (Hemiptera: Pentatomidae)”, were also consulted. Support for our research and outreach on BMSB comes from USDA-NIFA SCRI Award #2011-51181-30937. To learn more about BMSB biology, distribution, and management, please visit the following web site: StopBMSB.org