Each year as winter’s chill retreats and springlike temperatures climb into the 60s and 70s, many insects including stink bugs make their presence known both outdoors and inside our homes. Why all the activity at this time of year? The answer lies in age-old patterns of life crafted by insects in temperate zones to survive the ravages of winter. As we learned in previous episodes of Bug of the Week, many insects evolved clever adaptations such as antifreeze proteins and cryoprotectants that enable them to survive temperatures far below freezing. No such luck for other insects such as brown marmorated stink bugs (BMSB). BMSBs are classified as chill-susceptible, meaning they are intolerant of cold temperatures. Their survival in unprotected locations declines dramatically as temperatures drop near and below freezing (32 degrees Fahrenheit), as they did with the unrelenting polar vortex last winter. To survive in urban and suburban settings stink bugs depend on human-made structures for winter survival.
Millions of folks throughout the nation were treated to invasions of stink bugs last autumn as the horde sought refuge in homes, schools, and office buildings. Some people mistakenly believe that stink bugs enter buildings in winter to get warm, but this is not the case. In the natural world where stink bugs evolved over millions of years, there were no McMansions. Stink bugs sought winter refuge in sheltered spots beneath the bark of trees or in rocky crags. Protected from the onslaught of winter, stink bugs chilled out and entered a state akin to hibernation where their activity declined as they awaited the return of favorable temperatures and springtime food. Lengthening days and warm temperatures signal the return of leaves, flowers, and fruit. With the return of warmth and food sources, stink bugs answered Mother Nature’s wake-up call and moved from their refuges to the greening landscape. Ah, but humans build structures and provide other places for stink bugs to survive. Inside attics or beneath the siding of homes where stink bugs sheltered for the winter, warm days convince stink bugs that spring has arrived and that it is time to return to the wild to seek food and pursue the biological imperative of finding mates and reproducing. With many stink bugs wandering about, it appears that my home, like many others, proved to be an excellent choice for surviving the rigors of winter.
With the arrival of warm spring days, brown marmorated stink bugs that invaded homes in autumn try to escape to the world outdoors. Their appearance on computer screens, appliances, furniture, and calendars attest to their luck in choosing the thermal refuge of my home for overwintering. Stink bugs that invaded my unheated tool shed chose poorly. Prolonged periods of subfreezing temperatures resulted in high levels of mortality in the shed. Could severe cold in many parts of our country last winter translate into fewer stinkbugs this summer?
But not all choices of human-made structures are equal when it comes to surviving winter for BMSB. Choosing the right overwintering shelter is a matter of life and death for a stink bug. The business of shelter-choice by stink bugs reminds me of the famous line in the movie Indiana Jones and the Last Crusade. Hero Indy and villain Donovon must choose a potential Holy Grail cup from which to drink. The surviving Grail Knight warns Jones "Choose wisely, for while the true Grail will bring you life, the false Grail will take it from you.” Stink bugs face a similar choice. Based on the hordes of stink bugs running about, it appears that my home provided a thermal refuge from the winter of 2025 – 2026, classified as “severe” due to extended periods of nights and days below freezing. Well, what other choices were available to my neighborhood stink bugs? They had the option of overwintering in my unheated shed. And how did they fare? Maybe not as well. I visited several hundred stink bugs in my tool shed recently. Of hundreds I found littering the shed, less than 8% were still alive. In the words uttered by the Grail Knight, these stink bugs apparently “chose poorly”. These results are not surprising as several previous studies highlight the importance of different types of human-made shelters in providing suitable overwintering refuges for brown marmorated stink bugs.
Unheated sheds are a bad choice to overwinter in when winters are severe. Hundreds of stink bugs perished in my outbuildings last winter.
As you deal with stink bugs this spring, here are some things to consider. Some folks have asked if “stink bugs can breed in my home?” To the best of our knowledge, the answer to this question is no. In the normal course of events, stink bugs move from winter refuges to plants outdoors where they feed for several weeks before they become competent to lay eggs. In your attic or an unused bedroom there is simply no food to provide the sustenance needed by stink bugs to produce eggs. Even if a stink bug could lay eggs indoors on a windowsill or wall, there would be nothing to sustain the young bugs, which require plant food for growth and development. Having made this claim, I might back-peddle just a little, as we have received reports of stink bugs feeding on house plants such as orchids and potted ponytail palms. Will stink bugs lay eggs on houseplants indoors? One homeowner discovered a batch of stink bug eggs on a houseplant in the spring a few years ago. So, the final answer to this jeopardy question is yes, they might breed in your home. The chances of stink bugs sustaining a population in your home probably lie somewhere between zero and nil, unless you have bountiful fruit bearing plants in your home and do everything to ignore stink bugs dashing about on those plants.
Another question that always comes up: What should I do about stink bugs that appear in my home this spring? Sweeping, vacuuming, or simply picking them up and disposing of them is still our recommendation for control indoors. Because they will be active for a relatively long period of time, we are not recommending the application of insecticides to indoor living spaces to control stink bugs as they appear. Exposure of children and pets to pesticides could be worse than exposure to stink bugs. In fact, many pets and some children will be amused by a few stink bugs wandering about. My daughter’s cat loves them and, not surprisingly, my grandkids don’t fear the stink bug.
To learn more about the brown marmorated stink bug, please visit the following website: http://www.stopbmsb.org/
To learn what to do when stink bugs get inside, and how to keep them out, watch the following video: https://youtu.be/0kG-2fetbZA
Acknowledgements
Thanks to stink bug hunter Dr. Shrewsbury for providing inspiration for this episode. Great references including “Cold tolerance, water balance, energetics, gas exchange, and diapause in overwintering brown marmorated stink bugs” by John J. Ciancio, Kurtis F. Turnbull, Tara D. Gariepy, and Brent J. Sinclair and “Cold Tolerance of Halyomorpha halys (Hemiptera: Pentatomidae) Across Geographic and Temporal Scales” by Theresa M. Cira, Robert C. Venette, John Aigner, Thomas Kuhar, Donald E. Mullins, Sandra E. Gabbert, and W. D. Hutchison provided insights into the cold tolerance of BMSB.