Home sweet home bugged by uninvited winter guests

The brown marmorated stink bug (BMSB an insect pest with an unsavory name and an unappealing scent first showed up in Portland in 2004.

The brown marmorated stink bug (BMSB an insect pest with an unsavory name and an unappealing scent first showed up in Portland in 2004.

Cooler temperatures drive many insects indoors, including some exotic species

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.”

Because these pests 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 these pests 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 them. You can escort them outside, flush them down the toilet, or dispose of them as you see fit.”

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 Willamette Valley area.

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.

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.

  1. Rough stink bug, Brochymena affinis

  2. Arhyssus sp. 

  3. Box elder bug, Boisea rubrolineata

  4. Various color morphs of multicolored asian ladybird beetle, Harmonia axyridis

  5. Xanthochilus saturnius

  6. Tuxedo bug, Raglius alboacuminatus

  7. Elm seed bug, Arocatus melanocephalus

  8. Western conifer seed bug, Leptoglossus occidentalis

  9. Brown marmorated stink bug, Halyomorpha halys

  10. Big nose bug, Metopoplex ditmoides (with a silhouette to scale, as they are ~4mm in length.)


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