Jeffrey Hahn, Asst. Extension Entomologist
It has been a long summer but fall is finally catching up with us. Fall is also the time when nuisance insects fly to buildings and other structures to look for places to spend the winter. One insect to be on the watch for is the boxelder bug Although these orange and black insects are around every year, they have been particularly numerous this summer. The weather has a lot to do with that as years of hot, dry summers are very favorable for their development and we often experience much larger populations of them then.
Control is two fold. First, seal as many spaces and openings as possible that may allow boxelder bugs into your home. Concentrate around widows and doors, roof lines, where utility lines enter buildings, and where horizontal and vertical surfaces meet. Second, supplement this with a residual insecticide application, especially around areas where boxelder bugs are most likely to gain access. This is something homeowners can try themselves; common active ingredients that could be used would include permethrin and beta-cyfluthrin (make sure products are labeled for the outside of homes). Or they can contact an experienced pest management service to make this application for them.
Not only is it important to take action now to keep boxelder bugs out of your home this fall but a lot of these insects can also become nuisances later during days of mild winter temperatures. Once they get inside, they seek out wall voids, attics and other nooks and crannies in which to hibernate. It is important for boxelder bugs to find a place that is unheated and will remain cold during winter. As long as they are in such place, they will remain dormant.
However, as temperatures warm up the sites where boxelder bugs are hiding, they will wake up, 'thinking' spring has arrived. They will move towards the warmth and will end up being trapped indoors. Boxelder bugs typically aggregate in clusters; insects on the outer part of these clusters will become active first. This results in boxelder bugs emerging at different times. When boxelder bugs appear in the middle of the winter, it appears that they have been reproducing indoors, however what people are seeing are adults that entered their homes the previous fall. (Note: Boxelder bugs are occasionally observed laying eggs indoors. However, either immature boxelder bugs don't hatch from them or if they do the young bugs do not have food and do not live long. They certainly are not able to mature into adult bugs.)
The boxelder bugs that get inside your home can definitely be annoying; in fact the more there are the more bothersome they usually are. Fortunately, boxelder bugs are harmless to people. They may occasionally stain surfaces but are otherwise not damaging to property. Once they are in your home, you have few options to deal with them. The easiest solution is physical removal, such as with a vacuum cleaner. This may not always be helpful when boxelder bugs are really numerous, but that is still the best control. This is why the more you can prevent from entering your home during fall, the fewer you will deal with later.