The brown marmorated stink bug is Maryland’s most notorious household invader, arriving by the hundreds each fall as temperatures drop. Native to Asia, this shield-shaped insect first appeared in the mid-Atlantic region near Allentown, Pennsylvania in the mid-1990s and quickly spread into Maryland, where it now thrives in every county. If you’re dealing with stink bugs in your home or garden, here’s what you need to know about their behavior, timing, and the most effective ways to manage them.
How Stink Bugs Arrived in Maryland
The brown marmorated stink bug (often shortened to BMSB) was accidentally introduced to the United States from eastern Asia. After its initial detection in Pennsylvania, it spread rapidly through New Jersey, Maryland, Delaware, West Virginia, and Virginia. By 2003, it had been found in orchards across the region, and it has since established itself in agricultural areas including vineyards in Frederick and Washington counties.
Maryland sits at the heart of the stink bug’s adopted range. The state’s mix of farmland, suburban developments, and wooded areas provides ideal habitat for feeding, breeding, and overwintering. Unlike many invasive species that remain confined to rural areas, the brown marmorated stink bug is equally at home on a tomato plant and inside your attic.
When Stink Bugs Show Up
Stink bugs follow a predictable seasonal cycle in Maryland. Adults become active during the first warm days of spring, typically in April, when they leave their overwintering sites to feed and reproduce. Through the summer months, they feed on fruit, vegetables, and ornamental plants, and females lay clusters of pale green eggs on the undersides of leaves.
The real headaches start in fall. As nighttime temperatures begin to dip in September and October, adult stink bugs seek warm, sheltered spots to spend the winter. In nature, that means fence rows, grassy field borders, spaces under stones, or beneath tree bark. In suburban Maryland, it means your house. They’re drawn to sun-warmed exterior walls, especially south- and west-facing surfaces, and work their way inside through any gap they can find. Once inside, they enter a dormant state and typically stay hidden in walls, attics, and crawl spaces until spring warmth rouses them again, at which point they start appearing on windows and light fixtures as they try to get back outside.
Damage to Gardens and Crops
Stink bugs feed by piercing plant tissue with their needle-like mouthparts and sucking out juices. On fruit like tomatoes, peppers, peaches, and apples, this leaves behind dimpled, discolored spots that make the fruit unmarketable or unappetizing. On vegetables, feeding damage can cause distorted growth or corky, white patches beneath the skin. Home gardeners in Maryland frequently notice damage on tomatoes, beans, peppers, and sweet corn.
At the commercial scale, the impact has been significant. Maryland orchards and vineyards have reported substantial losses since the bug’s arrival, particularly in the western part of the state. The stink bug’s broad diet, which includes more than 100 plant species, makes it difficult to manage in diverse agricultural landscapes. It feeds on tree fruit, row crops, and ornamentals with equal enthusiasm.
A Tiny Wasp Is Helping
One of the more promising developments for Maryland’s stink bug problem arrived on its own. A parasitic insect called the samurai wasp, barely bigger than a sesame seed, was first detected in Maryland in 2014. This wasp is the same natural enemy that keeps stink bug populations in check across Asia. It lays its eggs inside stink bug egg masses, killing the developing nymphs before they hatch.
The samurai wasp is remarkably effective. In its native range, it parasitizes 60 to 90 percent of stink bug egg masses. It has since been found in at least 12 states and appears to be following the stink bug’s distribution westward from Maryland. While it hasn’t eliminated the problem, its presence is one reason some researchers believe stink bug populations in the mid-Atlantic may gradually stabilize over time rather than continuing to spike.
Keeping Stink Bugs Out of Your Home
Physical exclusion is the single most effective strategy. Stink bugs enter through cracks around windows, doors, siding, utility pipes, behind chimneys, and underneath wood fascia boards. A systematic inspection of your home’s exterior in late August or early September, before the fall migration begins, gives you the best chance of sealing entry points before the bugs arrive.
Use a good quality silicone or silicone-latex caulk to seal gaps and cracks. Pay special attention to where utility lines and pipes enter the house, where siding meets the foundation, and around window frames. Repair or replace any damaged screens on doors and windows. Attic vents and weep holes in brick can be covered with fine mesh screening. Even small gaps matter: stink bugs can squeeze through openings as narrow as a few millimeters.
Removing Stink Bugs Indoors
If stink bugs make it inside, your options are simple but important to get right. Crushing them releases the foul-smelling compound that gives them their name, so most people prefer gentler removal. A vacuum cleaner works well for collecting large numbers, though you’ll want to empty the bag or canister promptly into an outdoor trash bin to avoid lingering odor.
For a hands-off approach, researchers at Virginia Tech found that a homemade light trap outperformed commercial alternatives by a wide margin. The setup is straightforward: fill an aluminum foil roasting pan with water and a squirt of dish soap, then place a desk lamp directly over the pan in a dark room. The light attracts the bugs, they fall into the soapy water, and the soap breaks the surface tension so they can’t escape. In testing, this simple trap eliminated 14 times more stink bugs than store-bought traps costing up to $50.
There are currently no indoor insecticides labeled for use against brown marmorated stink bugs, which makes mechanical removal and trapping your best indoor tools. Exterior perimeter sprays applied by pest control professionals before fall can reduce the number that enter, but they won’t eliminate the problem entirely and need to be timed correctly to be worthwhile.
Why They Smell
The stink bug’s defining feature is the pungent, cilantro-like odor it releases from glands on its underside when disturbed or crushed. This chemical defense deters birds and other predators in the wild. Indoors, it means that swatting or squishing a stink bug leaves a lingering smell on your hands, walls, or carpet. The scent can also attract other stink bugs to the same area, which is another reason gentle removal (vacuuming, trapping, or sweeping into soapy water) is preferable to crushing them.