The Brown Marmorated Stink Bug (BMSB), an invasive species, is a common nuisance for homeowners and a significant agricultural pest. Understanding what attracts these insects is the most effective defense against their presence near human structures. Their attraction is driven by two primary needs: the search for food during warmer months and the need for warm, protected shelter as temperatures drop. Identifying these attractants allows people to take practical steps to reduce the likelihood of an invasion.
Preferred Food Sources and Habitats
During spring and summer, the brown marmorated stink bug is primarily attracted to food sources. This insect is a generalist feeder, using its piercing-sucking mouthparts to feed on over 120 different plant species, including agricultural products and ornamental plants. They are particularly drawn to plants bearing fruit or reproductive structures, such as buds and pods, which offer concentrated nutrients.
Their diet includes popular crops like apples, peaches, pears, figs, tomatoes, and corn, with a strong preference for mature fruit. The bugs locate these feeding sites using chemical cues released by the plants. Their presence in these areas, especially near homes, establishes a local population that will later seek shelter nearby.
The Seasonal Urge to Seek Shelter
The most noticeable attraction for homeowners is the insect’s movement indoors during late summer and fall, triggered by the biological need to survive winter. This annual migration is driven by environmental cues, specifically the shortening of daylight hours, which signals the approach of colder weather. This cue induces a state of winter dormancy known as diapause, which improves their cold tolerance.
The bugs are not seeking food inside the house; they are looking for a stable, protected location to enter this non-feeding dormant state. They seek overwintering sites that are dry and shielded from harsh weather, which human-made structures provide perfectly. Once in diapause, they remain inactive until the warmth of spring triggers them to emerge.
This biological imperative causes them to aggregate on the sunny, exterior walls of homes before crawling into any available crack or crevice. They utilize chemical cues, including aggregation pheromones, to attract other stink bugs to a suitable overwintering location, leading to mass invasions. The best way to prevent this attraction is to seal all potential entry points, such as utility penetrations, window frames, and foundation cracks, before the insects begin their seasonal search.
How Light and Visual Cues Draw Them Indoors
While the primary seasonal motivation is shelter, the immediate mechanism guiding stink bugs to an entry point is often light and other visual cues. Stink bugs exhibit a phototactic response, meaning they are attracted to light. They are drawn to various light sources, with white light being a particularly attractive stimulus, followed by blue light.
The attraction to light is most pronounced during the evening hours when they are actively seeking entry. Artificial light sources like porch lights, floodlights, and light leaking from windows can draw them directly to an entryway. The contrast of a dark house against a brightly lit surface, or the vertical nature of a structure, can also serve as a visual landmark for their movement.
To minimize this attraction, homeowners can switch exterior white lights to less attractive yellow or amber LED bulbs, which have a longer wavelength that insects are less sensitive to. Turning off unnecessary outdoor lighting during the evening hours of the fall migration season can significantly reduce the number of bugs drawn near potential entry points.