With our planet reaching the unenviable landmark of experiencing the warmest February on record and the warmest 12-month period in history, March temperatures keep marching right along with more projected highs near 70. As predicted, record warmth in temperate zones like the DMV means that insect activity will begin earlier and extend later each year than it has in years past. Not only will the action start earlier outdoors, but insects that have overwintered in our homes will be on the move earlier as refuges in attics and various nooks and crannies around our homes heat up. With temperatures now in the mid to upper 60s, home invaders like stink bugs are on the move in homes and offices, accumulating on windowsills, walls, and doors and buzzing about indoor lights at night. Why all the activity at this time of year?

In autumn stink bugs seek shelter in attics, beneath siding, and behind shutters.

The answer lies in the age-old pattern of life crafted by stink bugs to survive the ravages of winter and emerge just in time to take advantage of bountiful leaves and fruit found on plants in the spring. 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. Many people mistakenly believe that stink bugs enter buildings in winter to ‘get warm’, but this is not the case. In the natural realm where stink bugs evolved over millions of years, 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 season of inactivity akin to hibernation where they awaited the return of favorable temperatures and springtime food. Lengthening days and warming temperatures signaled the return of leaves, flowers, and fruit. With the return of food sources, stink bugs answered Mother Nature’s wake-up call and moved from their refuges to the greening landscape. During the past week with warm weather, flowers, leaves, and yes, pollen, exploded on trees, shrubs, and herbaceous plants in the Washington metropolitan region. Inside attics or beneath the siding on homes, these warm days have convinced 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 laying eggs. On warmish days this winter, every now and then I collected a stink bug or two wandering about the kitchen or living room. But as of this week, these occasional sightings have turned into a steady stream and I collect stinkers daily.

As you deal with stink bugs this spring, here are some things to consider. Recently, I was asked if “stink bugs 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 laid 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 lies 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 is “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 of children and pets to stink bugs. In fact, many pets and some children will be amused by a few stink bugs wandering about.

Window sills collect stink bugs on warm days in late winter and spring as they attempt to exit homes.

Will stink bugs be as problematic this year as they were in the watershed years of 2010 and 2012? Probably not. Although stink bugs have now spread to 47 states and 4 Canadian provinces, in our region most people agree that fewer stink bugs plagued gardens, homes, and farms recently than they did several years ago. Fascinating studies suggest that a combination of climatic events and Mother Nature’s Hit Squad of predators, parasitoids, parasites, and pathogens have conspired to smack down populations of stink bugs. Scientists at Virginia Tech found that rapidly plunging temperatures associated with weather phenomena such as the polar vortex may reduce survival of overwintering stink bugs. Studies conducted at the University of Maryland revealed that young stink bugs thrive only when the proper complement of microbes are present in their gut. These microbes pass from mother to offspring when youngsters consume exudates smeared on the surface of their eggs by their mother. Without this complement of microbes, survival and development of stink bugs is reduced. Authors suggest that high temperatures may harm this microbiome and thereby reduce colonization by stink bugs. Maybe our record warmth does some good after all.

With respect to Mother Nature’s Hit Squad, in previous episodes of Bug of the Week, we met vicious predators such as the Chinese Mantis, Wheel Bug, and Black and Yellow Garden Spider as these feasted on stink bugs. Scientists at the USDA found several species of indigenous predators such as ground beetles and katydids attacking eggs of stink bugs in orchards and vegetable crops. Researchers at the University of Maryland discovered several species of tiny native wasps metering out significant mortality on eggs of stink bugs in ornamental plant nurseries. And yes, stink bugs are susceptible to pathogens as well. Scientists at Cornell have described a tiny microsporidian parasite called Nosema maddoxi infecting several populations of stink bugs around the nation. Collectively, weather events and natural enemies are helping humans to win the war on one of the most serious recent invaders to arrive in our country.

Acknowledgements

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

The following articles were used to prepare this episode: “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. “The Importance of Gut Symbionts in the Development of the Brown Marmorated Stink Bug, Halyomorpha halys (Sta˚l)” by Christopher M. Taylor, Peter L. Coffey, Bridget D. DeLay, and Galen P. Dively. “Frequency, efficiency, and physical characteristics of predation by generalist predators of brown marmorated stink bug (Hemiptera: Pentatomidae) eggs” by William R. Morrison III, Clarissa R. Mathews, and Tracy C. Leskey. “Field surveys of egg mortality and indigenous egg parasitoids of the brown marmorated stink bug, Halyomorpha halys, in ornamental nurseries in the mid-Atlantic region of the USA by Ashley L. Jones, David E. Jennings, Cerruti R. R. Hooks, and Paula M. Shrewsbury. “Nosema maddoxi sp. nov. (Microsporidia, Nosematidae), a Widespread Pathogen of the Green Stink Bug Chinavia hilaris (Say) and the Brown Marmorated Stink Bug Halyomorpha halys (Stål)” by Ann E. Hajek, Leellen F. Solter, Joseph V. Maddox, Wei‐Fone Huang, Alden S. Estep, Grzegorz Krawczyk, Donald C. Weber, Kim A. Hoelmer, Neil D. Sanscrainte, and James J. Becnel.