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Bug of the Week is written by "The Bug Guy," Michael J. Raupp, Professor of Entomology at the University of Maryland.

Stink bugs on the move: Brown Marmorated Stink Bug, Halyomorpha halys


This brown marmorated stink bug is looking for just the right crack, crevice or home in which to spend the winter.


The closing days of September and opening days of October mark the time that brown marmorated stink bugs are on the move. This weekend on a gorgeous afternoon up on Sugarloaf Mountain, other trekkers and I were greeted by swarms of stink bugs cavorting on trees and stones near the rocky mountaintop. Upon returning home from my hike, I found a dozen stink bugs plastered on the side of my home gazing through the window. 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. Ah, but this cornucopia of earthly delights soon wanes for the stink bug.  

In the waning days of summer stink bug nymphs fatten-up on delectable vegetables like this tomato.

In 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 standstill. Prior to this inimical season, stink bugs seek refuges to chill-out where they are protected from the harsh weather and dangerous predators.

Stink bugs check out a shutter as a potential winter refuge.

Why do stink bugs enter homes and man-made structures? Many folks incorrectly believe they enter homes to be warm for the winter. 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 wonderful place for stink bugs to crawl under and escape the ravages of winter. Rocky ridge tops appear to 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 may seem like a remote problem. However, the nuisance potential of brown marmorated stink bug 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!

Loose bark, rock crevasses, and homes provide overwintering refuge for the brown marmorated stink bug. 

While populations of brown marmorated stink bugs 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. Some believe the polar vortex last winter greatly reduced numbers of stink bugs in our region. Others believe that indigenous 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).  It is likely that a suite of factors and events conspired to reduce stink bug numbers in our region. Let’s keep our fingers crossed that this trend continues while we await the autumnal arrival of these home invaders.



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, 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 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: