Stinkin Overwintering Pests

It’s a beautiful fall day, and through my open windows I can appreciate the changing of seasons. Buzzzz…. clunk! But there it is again, a sound that brings frustration and anxiety. Hesitantly, I glance over from my typing machine and observe the small 5-sided body creeping along the screen. It pauses, orients, and starts moving again as it looks for an entry point around the window frame. And so begins another invasion by the brown marmorated stink bug!

The brown marmorated stink bug (BMSB) and I share a long history. I went to college in Allentown, Pennsylvania, where this insect first arrived in the US on a shipment from the Orient. With piercing/sucking mouthparts, this BMSB feeds on plant juices, damages fruit and renders apples, pears, peaches, and other fruits aesthetically unacceptable for sale.

During summer months, stink bugs feed on a variety of host plants and large numbers can be found in agricultural fields. Their reign of terror continues into the fall, when adults seek overwintering sites to protect them from harsh winter conditions.

Around widows and doorframes in our Allentown dormitories, we encountered so-called “crunchy bugs” that made a pungent odor when crushed. The BMSB has since spread to several states, and is reported as for north as Maine, south to North Carolina, and west to Michigan with new populations in Wisconsin and Washington. A once unknown pest, the BMSB now receives great attention at trade shows and other events to which I bring my insect display. When viewing the 3/4 inch, brown, shield shaped insect, onlookers protest, “how do I get rid of stink bugs?!”

The BMSB belongs to the pest management professional’s category of “overwintering pest,” which also includes the Western conifer seed bug, the multicolored Asian ladybird beetle, the boxelder bug, and cluster flies. As fall approaches and important cues such as cooler temperatures, shorter days, and decreased quality of host-plant material arrives, these insects start their assault on homes and other structures.

Why? In their natural habitat, overwintering insects seek southwest-facing, light-colored structures such as rocks that are warmed by afternoon sun. These areas provide some protection and buffering against cold winter temperatures, and enhance survival of the insects. Where buildings have replaced natural landscapes, these structures now provide similar cues to insects preparing for winter.

Some overwintering pests use pheromones to form large aggregations, later fleeing to enter buildings. For the most part, overwintering pests cause no damage for the homeowner. However, some species can bite and leave fecal stains (boxelder bug), while a mass of dead insects (ladybird beetles) is displeasing to homeowners.

The best way to address overwintering pests is also the most difficult: exclusion. These insects are adapted to exploit tiny cracks and crevices leading to safe harborage areas. Eliminating entry points is a guaranteed way to provide long-term control. Here are just a few tips to keep overwintering pests out of your home.

1. Screen exterior vents that lead into the home
2. Seal pipe chases and openings around wires with expanding foam
3. Eliminate cracks, crevices, and openings around doors, window frames, fascia, etc. with caulk (silicone)
4. Replace or repair damaged screens or doors
5. Remove window air conditioning units that provide direct access to interior

If you experienced an infestation in the past, or have recently observed large numbers of insects invading your home, consult your pest management professional for treatment options.