Yes, they’re back and they’re right on time. The brown marmorated stink bugs (BMSB) have certainly made a name for themselves in eastern Nebraska for invading houses. Over the last few years, they’ve become known as a structural pest and indoor nuisance.

Entomologists call them fall invaders or incidental invaders, due to the timing of their invasions into our spaces. BMSB begin to move by the dozens and sometimes hundreds into homes, schools, sheds, outbuildings, and other structures just after the autumn equinox. We are not sure why some buildings attract more BMSB than others, but homeowners often complain about being a favored overwintering site year after year.

The good news is BMSB do not cause any damage to the structure and they are not harmful to humans. They do not bite or spread disease. They will not reproduce indoors. They are “true bugs” (Hemipterans) with piercing-sucking mouthparts, used to feed on fruits, vegetables, and ornamental plants. When threatened or crushed, they release a strong, putrid, stinky odor.

Fall is the time to get out and look around your house. It is the time to manage populations of BMSB in order to minimize the number of bugs that want to get in for the winter. Fall is the time to prevent, exclude, remove, and treat with insecticide (if you choose). An effective integrated pest management program is all about knowing the pest biology and behavior and taking action at the proper time. So, the time is now!

Identification

Although BMSB undergo five nymphal stages, they overwinter as adults. Like other stink bugs, BMSB adults are recognized by their shield-like body shape. There are several brown stink bugs found in the landscape, but BMSB can be identified by the following:

• Mottled or marbled (marmorated) brown color pattern
• Alternating dark and light bands on the margin of the abdomen
• Smooth “shoulders”
• White bands on antennae

Tips for Managing BMSB in the Fall

Here are some things you can do to prevent and exclude BMSB from entering the structure:

1. Use caulk or sealant for gaps around utility openings, door and window frames, vents, and other cracks and crevices that allow entry into home.
2. Fix or replace weather-stripping around doors and windows.
3. Keep doors and windows closed or make sure they are properly screened.
4. Remove debris such as firewood, leaf litter, and yard items from around foundation where BMSB hide.

Stink bugs start to aggregate on the warmest side of the home (usually south or west wall) and crawl upward toward the eaves, fascia, soffits, chimney, and roof overhang. If you see a large number of BMSB, hose them down and/or brush them off into a bucket of soapy water.

Professional pest management companies may provide exterior insecticide treatments and there are products available to homeowners, but timing is very important. If the residual is applied too early, it may break down in the sunlight, and if it is applied too late, the BMSB may have already entered the structure. Be sure to read and follow the label.

After the Fall

Once they’re in and you spot one or two during the winter, there is little you can do. There are likely several overwintering inside the structure, in wall voids, and attic spaces. BMSB become active on sunny days when their habitat warms up. Homeowners see them come out from behind curtains, window screens, and light fixtures, flying around as an indoor pest. Unfortunately, the best way to eliminate BMSB at this point is to trap each one and drop in soapy water. Squishing or vacuuming results in the stink, and using insecticides indoors is not effective and may pose more of a risk than a solution.

In the spring, it will be equal feelings of frustration, but the reverse action, as overwintered BMSB will want to get out! Prevention and exclusion now, will be the best form of management. Good luck!

Resources:

My predecessor, Dr. Jonathan Larson, wrote a blog post about these invasive little stinkers in 2018, Four Things to know about Brown Marmorated Stink Bug.

A Bug’s Life: Brown Marmorated Stink Bug

Stop BMSB: Management of Brown Marmorated Stink Bugs in US Specialty Crops

Jody Green, PhD

Extension Urban Entomologist at Nebraska Extension

Jody Green is the extension urban entomologist at Nebraska Extension in Douglas-Sarpy Counties. She specializes in structural, household, and health-related insect pests.