As fall temperatures begin to drop, Maryland pest management professionals can expect an increase in customer complaints about brown marmorated stink bugs (Halyomorpha halys). These insects often gather in large numbers on the exterior of homes and commercial buildings before finding their way indoors to spend the winter.
While customers may expect an insecticide treatment to solve the problem, effective management requires an understanding of stink bug behavior, careful inspection, and a focus on exclusion.
Native to parts of Asia, the brown marmorated stink bug was first observed in the United States in Allentown, Pennsylvania, in 2001. It later established populations in Maryland and has become a familiar seasonal nuisance.
In late summer and early fall, adult stink bugs begin seeking protected overwintering sites. They are strong fliers and often gather on warm, elevated building surfaces before entering through cracks and other openings.
Once inside, they may remain hidden in wall voids, attics, and other protected areas until warmer temperatures trigger activity.
Although their numbers can be alarming to customers, brown marmorated stink bugs do not bite, sting, damage wood, or spread disease. Their primary impact inside structures is as a nuisance pest.
Understanding this behavior is important when developing a management plan and explaining realistic treatment outcomes to customers.
Mechanical exclusion remains the most effective way to prevent brown marmorated stink bugs from entering structures.
During fall inspections, PMPs should pay particular attention to potential entry points, including:
Gaps around windows and exterior doors
Cracks and openings in siding
Utility pipe penetrations
Openings around chimneys
Gaps beneath fascia boards
Damaged or improperly fitted window and door screens
These openings should be sealed with appropriate materials, such as high-quality silicone or silicone-latex caulk. Damaged screens should be repaired or replaced.
Interior sightings can also provide clues about where stink bugs are entering occupied spaces. Common locations include gaps beneath or behind baseboards, around window and door trim, and near ceiling fixtures, lights, and exhaust fans.
Technicians should explain that sealing exterior entry points before insects move indoors is more effective than attempting to eliminate stink bugs after they have entered wall voids or attic spaces.
Once stink bugs have entered a building, insecticide applications generally provide limited benefit.
University of Maryland Extension does not recommend aerosol foggers for stink bugs that have accumulated on walls and ceilings. These applications may fail to eliminate the insects and will not prevent additional bugs from entering.
Similarly, applying insecticides into cracks, crevices, wall voids, or attic spaces is not considered an effective long-term management strategy.
Treating hidden populations may also create secondary pest problems. Dead stink bugs can become a food source for carpet beetles, which may subsequently damage woolens and other susceptible materials.
For accessible stink bugs, physical removal is often the preferred approach.
Vacuuming can efficiently remove insects from walls, windows, and other indoor surfaces. However, technicians should be aware that disturbed or crushed stink bugs release an unpleasant odor. Vacuum collection bags and canisters may retain that smell temporarily.
Stink bugs can also be collected and disposed of in soapy water.
These methods help reduce immediate nuisance activity without unnecessary pesticide applications.
Exterior insecticide applications may provide some relief when complete structural exclusion is difficult or impossible. However, University of Maryland Extension generally does not recommend relying on insecticides for brown marmorated stink bug management.
Where an appropriately labeled product is selected, timing is important. Applications made in the fall, just before stink bugs begin congregating on structures, have a better chance of contacting incoming insects than treatments made after they have entered protected spaces.
The Extension publication identifies several synthetic pyrethroid active ingredients that have been used for exterior stink bug control, including deltamethrin, cyfluthrin, lambda-cyhalothrin, cypermethrin, sumithrin, and tralomethrin.
However, technicians should recognize that sunlight can break down insecticide residues, reducing their effectiveness within days or approximately a week under some conditions.
Even when properly applied, exterior treatments may not provide the level of control customers expect.
PMPs must use products currently registered for the intended application and follow all label requirements, including approved treatment sites, application methods, and environmental precautions.
Customer communication is an important part of successful stink bug management.
Technicians should explain that brown marmorated stink bugs seek shelter in buildings as temperatures change and that insects already inside wall voids may continue to appear in living spaces even after exterior openings have been sealed.
A few points can help customers understand the management process:
Prevention works best before entry. Fall inspections and exclusion should be completed before large numbers of stink bugs begin entering structures.
Indoor sightings do not always indicate an ongoing infestation. Stink bugs may emerge from concealed overwintering sites as indoor temperatures change.
Insecticides have limitations. Treatments may reduce some activity but cannot guarantee that additional stink bugs will not enter.
Physical removal is often the most practical solution indoors. Vacuuming accessible insects can provide immediate relief without unnecessary pesticide exposure.
Setting these expectations before treatment can help avoid misunderstandings, repeated service calls, and customer frustration.
Brown marmorated stink bugs are a predictable fall nuisance, but their behavior makes them difficult to manage through insecticide applications alone.
A successful service approach begins with identifying entry points, recommending or performing appropriate exclusion work, removing accessible insects, and explaining the limitations of chemical control.
By emphasizing prevention and realistic expectations, pest management professionals can help customers manage seasonal stink bug activity while avoiding unnecessary treatments.
Source: University of Maryland Extension, Tips for Dealing With Brown Marmorated Stink Bugs, updated March 1, 2021. Original publication includes material adapted from Penn State Extension.