Home sweet home bugged by uninvited winter guests, Nov. 11

The welcome mat outside your home’s front door probably isn’t intended for all species of life, especially those with lots of legs. Nonetheless, many insects jump at the chance– or more likely crawl– to find a cozy shelter as winter approaches. Oregon homeowners and apartment dwellers may notice the usual increased indoor activity of insects associated with this time of year. “During fall and winter, several insect species– both introduced and native– can enter homes in large numbers,” says Oregon Department of Agriculture entomologist Jim LaBonte. “They may be a nuisance but homeowners should not be overly concerned with these bugs. They are not a threat to humans, pets, or structures in any way, manner, or form.” As temperatures drop and days become shorter, these insects can aggregate in houses and other structures. In nature, they seek winter shelter under loose bark, in rock crevices, rotten logs, and leaf litter. Unfortunately, human residences also work just fine as shelters. When such insects enter homes in large numbers, they can become what entomologists refer to as AHPs– aggregative house pests. Because AHPs are relatively small– some species are very tiny– they can easily enter through gaps under and around doors leading outside, poorly fitting windows, dryer vents, and other points of access into a residence. While almost all species of AHPs feed on plants, they do not feed while overwintering and should not harm house plants. These insects do not reproduce while inside homes. Keeping these bugs out in the first place is probably the best choice for residents. “The best thing to do is to seal up points of access,” says LaBonte. “For bugs that have already entered the home, it depends on how many you have and your tolerance for AHPs. You can escort them outside, flush them down the toilet, or dispose of them as you see fit. If there is a large number of them, a vacuum cleaner works well. We don’t recommend calling a pest control company this time of year. First, these bugs aren’t harmful. You should be able to deal with them on your own. Secondly, your home is like an island in a sea of bugs. Spraying pesticides, might get rid of pests inside the house at that time, but others likely will come in and take their place, especially if you haven’t sealed the accesses.” After a few hard frosts, the outdoor bugs will likely become very inactive or will have already found shelter for the winter. In either case, they aren’t likely to come indoors. Several native species find their way into the home during winter, most commonly the box elder bug, Boisea rubrolineata, which normally feeds on maple leaves. ODA has received calls about the native western conifer seed bug, Leptoglossus occidentalis, a leaf-footed bug sometimes mistaken for the “conenose” or “kissing” bug.  That bug is a species of assassin bug, which bites people, sucks their blood, and can transmit Chaga’s disease. However, “conenose/kissing” bugs are not found in Oregon. Over the past dozen years, a handful of exotic species have burst onto the local scene in high numbers. One insect pest with an unsavory name and an unappealing scent first showed up in Portland in 2004. At the time, it was the first appearance of the brown marmorated stink bug (BMSB), Halyomorpha halys, west of the Mississippi. Since then, the bug has become established throughout Oregon, with large populations in the Portland area, covering the south to Jackson and Josephine counties, and east to Umatilla and Union counties. BMSB– native to Asia– is similar in looks to some Oregon’s native stink bugs, but is not affected by the natural predators, parasites, or diseases that help control native stink bugs. Where established, it can enter homes by the thousands, which can be stressful and disturbing to residents. BMSBs can release an unpleasant odor when disturbed but are otherwise harmless to people. However, unlike other AHPs, they are a major concern for Oregon agriculture. “Brown marmorated stink bug is a major crop pest in the east and now, as anticipated, Oregon growers are starting to see damage, especially in apples and hazelnuts,” says LaBonte. “The insect feeds on more than 300 species of plants and commodities ranging from fruit to soybeans, and practically everything in between. It can reach high numbers and do a lot of damage just feeding on fruits and vegetables, rendering these commodities worthless in the marketplace. It can even damage trees by feeding on sap through the bark. No pesticides labeled for stink bugs are very effective against this species. There are no effective traps and lures commercially available for the insect pest, although research is promising.” ODA is collaborating with Oregon State University and U.S. Department of Agriculture on research regarding a tiny wasp, Trissolcus japonicus, that parasitizes the eggs of BMSB. This wasp is a natural enemy of BMSB and could help control this pest. The wasp is currently being reared in quarantine labs and may eventually be released on a national level. Accidentally introduced populations of the wasp were recently found in Portland. Plans to use these populations to spread the wasp elsewhere in Oregon are being considered. Several other exotic species distantly related to the brown marmorated stink bug have also been reported as being AHPs in Oregon. These include the big-nosed bug, Metapoplax ditomoides, and the tuxedo bug, Raglius alboacuminatus. Elm seed bug, Arocatus melanocephalus, has been more of an indoor pest in the summer as it goes into homes to avoid the heat. Found only where elms are present, the elm seed bug can also emit a foul odor when crushed or killed. Like other AHPs, none of these are problems otherwise. House or ground spiders often enter homes this time of year, especially while seeking mates. These spiders are nothing to be concerned about, according to LaBonte. The only truly poisonous Oregon spider is the black widow, which is rarely common in residences except perhaps in eastern or southern Oregon. It appears to be a normal year of indoor bug activity in Oregon. ODA is receiving fewer reports of brown marmorated stink bugs in homes, but that may be a sign of Oregonians just getting used to having them around. No matter the species, its normal for you to share your home this winter with insects whether you like it or not.