Two invasive insects shape Maryland’s fall pest season more than any others: the brown marmorated stink bug and the spotted lanternfly. Both arrived from Asia, both have spread widely across the state, and both produce the kind of large, visible nuisance that gets homeowners reaching for the phone. They are different insects with different habits, though, and the right response to each is not the same. This guide covers both.
The brown marmorated stink bug
Maryland has a longer history with the brown marmorated stink bug than almost any state. The insect first arrived in North America near Allentown, Pennsylvania, in the mid-1990s, roughly 100 miles from Baltimore. From that epicenter it spread rapidly down the I-95 corridor, and Maryland was among the first states to experience economically significant infestations, in both agriculture and homes. Western Maryland, around Hagerstown, was an early hot spot given its proximity to the Pennsylvania origin.
Identification. The brown marmorated stink bug is a shield-shaped insect about three-quarters of an inch long, mottled brown, with the marbled pattern that gives it the name “marmorated.” The most reliable identifying features are the alternating light and dark bands on the antennae and along the edge of the abdomen. When crushed or disturbed, it releases the sharp, pungent odor stink bugs are known for.
Why Maryland sees so much of it. Beyond the early-arrival history, Maryland’s mix of agriculture, suburban tree canopy, and gardens gives the stink bug plenty of host plants, it feeds on hundreds of species, and plenty of homes to overwinter in. The insect’s whole life cycle suits the state.
The fall invasion. This is what most Maryland homeowners experience. As the weather cools in September and October, brown marmorated stink bugs look for sheltered places to spend the winter, and the warm exterior walls of houses are exactly what they seek. They mass on south- and west-facing walls, the ones the afternoon sun warms, by the dozens and sometimes the hundreds. From there they work their way into wall voids, attics, and the spaces behind siding and around window frames. On warm winter days and again in early spring, they become active and head toward the light, which is why homeowners find them on interior windows.
What works. The single most effective measure is sealing the exterior before the stink bugs get in. That means a careful pass before the first cool snap: caulk gaps around windows and doors, seal where utility lines enter, check siding and trim, screen vents, and close gaps along the roofline. Once the stink bugs are inside the wall voids, options narrow. Spraying inside a wall void does little. Vacuuming up the ones that appear indoors is the practical response, and a vacuum with a disposable bag is better than crushing them, which releases the odor. For a home that takes them in heavily, a professional exterior treatment, focused on exclusion and a perimeter application timed for fall, is more effective than anything from a store shelf. The brown marmorated stink bug profile covers the insect in more detail.
The good news, such as it is: brown marmorated stink bugs do not bite, do not breed indoors, and do not damage the structure of a house. They are a nuisance, not a danger to the home.
The spotted lanternfly
The spotted lanternfly is the newer arrival, and it works very differently. First detected in Pennsylvania in 2014 and in Maryland in 2018, it has spread quickly. As of 2026, the entire state of Maryland is under a spotted lanternfly quarantine, covering all 23 counties and Baltimore City. The densest established populations are in central Maryland, the Baltimore, Howard, Montgomery, Prince George’s, Carroll, and Frederick county area. Harford County, around Bel Air, was one of the first areas placed under quarantine.
Identification. Adults are about an inch long, with wings held tent-like over the body at rest. The forewings are pale gray with black spots; when the wings open, the hind wings show a vivid red and black pattern. Adults appear from late July through October. Younger nymphs are small and black with white spots; the later nymph stage adds red patches. Egg masses, laid from September into winter, look like dried mud or putty smeared on bark, stone, vehicles, and outdoor furniture.
Why it matters in Maryland. Unlike the stink bug, the spotted lanternfly is fundamentally a plant and tree pest, not a structural one. It feeds by sucking sap from stems, leaves, and bark, and it threatens grapevines, hops, fruit trees, and hardwoods. Its preferred host is tree-of-heaven, an invasive tree common along Maryland roadsides and disturbed ground. In late summer and fall, lanternflies congregate in dense numbers, and heavy feeding produces a sticky waste called honeydew that coats decks, furniture, and cars and grows black sooty mold. That mess is the most common homeowner complaint.
What works, and what does not. This is the key point: spotted lanternfly is not a structural pest, and spraying your home’s foundation does nothing against it. It is a plant pest, managed in the plant environment. What genuinely helps:
- Scraping egg masses. From October through early spring, scrape egg masses off bark, stone, vehicles, and outdoor furniture into a bag with rubbing alcohol or hand sanitizer, and seal it. This requires no chemicals and reduces the next generation. It is the most useful thing a homeowner can do.
- Circle traps on tree-of-heaven and other host trees intercept nymphs moving up the trunk, without pesticide.
- Targeted treatment of high-value plants. For grapevines, fruit trees, or prized ornamentals, several contact insecticides are effective, and a licensed applicator can advise on what is appropriate for your site and plants.
- Removing tree-of-heaven from your property reduces the most attractive host. Note that tree-of-heaven resprouts aggressively, so removal needs to be done correctly.
The spotted lanternfly profile covers the insect, the quarantine, and management in more detail. If you find egg masses in volume, reporting them to the Maryland Department of Agriculture helps the state track the spread.
Two pests, two responses
It is worth being clear on the difference, because homeowners often lump these two together.
The brown marmorated stink bug is a structural-invasion problem. It comes into the house to overwinter, and the response is sealing the exterior and, for heavy cases, a professional perimeter treatment.
The spotted lanternfly is a plant problem. It does not come inside to live, and the response is egg mass scraping, traps, host-tree management, and targeted plant protection, not foundation spraying.
Both are most visible in the same season, late summer into fall, which is part of why they get confused. Both are invasive, both are widespread in Maryland, and both are here to stay.
When to call a professional
For the brown marmorated stink bug, a professional makes sense when a home takes them in heavily each fall and you want an exterior exclusion and perimeter treatment done right before the season. You can get connected with a licensed Maryland exterminator who handles this as part of residential pest control.
For the spotted lanternfly, there is no standard recurring pest control service, because it is not a structural pest. If you have grapevines, an orchard, or high-value ornamentals and lanternfly numbers are building, a consultation with a licensed applicator or a certified arborist before the population peaks is worthwhile. For most homeowners, though, the egg-mass scraping and host-tree management are work you do yourself.
Maryland’s fall belongs to these two insects. Knowing which is which, and matching the response to the pest, is what keeps the season manageable.