Brown marmorated stink bug
An invasive stink bug from East Asia, first collected in Allentown, Pennsylvania, in 1998, and the stink bug that moves into houses. It is a pest twice over. In summer, adults and nymphs pierce tomatoes, peppers, beans, sweet corn and tree fruit, leaving sunken white or yellow blotches and misshapen fruit. From September, adults gather on sunny walls and squeeze indoors to spend the winter. Indoors they do not bite, breed or damage the house, but they smell when crushed. Seal the house before autumn and vacuum up any that get in. In the garden, use row covers and hand-picking; sprays do little against adults.
Adult Halyomorpha halys on a ripening tomato, showing the white antennal bands and banded abdominal edge. Photo: pending.
Identification
Adults are shield-shaped, about 14–17 mm (5/8 inch) long, and mottled — marmorated — brown, with metallic punctures on the head and thorax. The reliable tells are two white bands on each antenna, alternating light and dark bands around the edge of the abdomen, dark bands on the membranous tips of the forewings, and smooth, rounded shoulders. Eggs are barrel-shaped and about 1.3 × 1.6 mm (Penn State), laid side by side on leaf undersides in masses of 20–30 (NC State gives an average of 28). Sources describe the eggs as white to pale green (UC IPM) or light yellow to yellow-red (Penn State). The five nymph stages range from about 2.4 to 13 mm (Penn State gives 2.4–12 mm; NC State 1/10–1/2 inch), with red eyes, a yellowish-red to off-white abdomen spotted red, and white bands on the antennae and, in some stages, the legs.
Several native bugs look similar, and one is a friend. The spined soldier bug (Podisus maculiventris) is a predator, and StopBMSB lists it among the native insects that eat BMSB: its shoulders end in sharp points, its beak is shorter and thicker, and its antennae are often reddish rather than white-banded. Leave it alone. The rough stink bugs (Brochymena) have a tooth on each side of the face and a row of spines along the shoulders; they eat both plants and insects. The brown, dusky and one-spot stink bugs (Euschistus) have more pointed shoulders and yellowish, faint antennal bands. The wheel bug hunts stink bugs and should also be left.
Easily confused with
- Spined soldier bugBeneficial — leave itThe predator has sharp spines on the shoulders, and the first segment of its beak is shorter and thicker; BMSB has smooth, rounded shoulders and two white bands on each antenna.
- Rough stink bugHarmlessRough stink bugs have a toothed shoulder edge, a two-pointed front to the head and no white bands on the antennae.
- Consperse stink bugAlso a pestIt has banded abdomen edges like BMSB, but its antennae are plain and its legs carry dark spots rather than white bands.
- Boxelder bugAlso a pestBoxelder bugs are brownish-black with three red stripes down the thorax and red wing margins; BMSB is a mottled brown shield with white-banded antennae.
Damage symptoms
Stink bugs feed with piercing-sucking mouthparts, injecting enzymes that break down the tissue before they suck it out. The damage is discolouration and collapse, not holes. Virginia Tech notes that on tomato and pepper it significantly reduces the fruit's market value. On sweet corn and peaches, the damage may not show on the outside but is obvious when the fruit is cut open. In the house the only harm is the smell, the droppings and the numbers.
- Tomato and pepper: white or yellow scars where the bug fed, sunken where the flesh beneath has collapsed — "cloudy spot"
- Pepper: white, spongy tissue under the feeding site
- Apple, pear and peach: pockmarked, distorted "cat-faced" fruit
- Sweet corn: aborted, collapsed or discoloured kernels, often only visible once husked
- Beans: scarred, sunken pods, deformed pods and browned seeds
- From September: bugs clustering on sunny outside walls, then emerging indoors around windows, baseboards and fans
Lifecycle & degree days
Adults spend the winter in dry, confined spaces. NC State notes it is the only stink bug in the state that seeks out buildings to do so — attics, garages, behind picture frames, in tarps and curtains. They do not feed or breed while overwintering. In Pennsylvania they leave shelter from late April to mid-May, mate and lay eggs from May to August, and start looking for overwintering sites from September through October. There is usually one generation a year in Pennsylvania, two in a warm year; UC IPM gives one or two for the mid-Atlantic. We found no degree-day model for garden use in the extension sources checked.
- Generations / yr
- 1 in Pennsylvania (2 in warm years); 1–2 mid-Atlantic
- Egg-laying
- May to August (Pennsylvania)
- Nymph instars
- 5
- Into buildings
- September to October
- Overwinters
- Adults, in dry sheltered spaces incl. houses
Host crops
BMSB feeds on more than 170 known plants. In gardens, NC State lists tomatoes, peppers, okra, green beans, soybeans, corn, Swiss chard, peaches, apples, pears, plums and caneberries. Its preferred wild hosts include tree-of-heaven, paulownia, catalpa, wild cherry and black walnut.
Monitoring & action thresholds
None of the extension sources checked gives a home-garden number; their advice is to act on what you find — crush egg masses, hand-pick bugs, cover plants — rather than to count. For the house there is no threshold either: exclusion is done before autumn.
From midsummer, check tomatoes, peppers, beans and fruit trees for adults, nymphs and egg masses on leaf undersides; crush egg masses and knock bugs into a jar of soapy water. Pheromone traps are sold, but StopBMSB warns that traps placed near plants can draw more bugs in and increase damage — keep any trap well away from the plants you want to protect. In late summer, watch the sunny sides of the house: bugs clustering there in September are the ones looking for a way in.
Biological control
No beneficial you can buy is recommended for BMSB. Its most promising enemy, the samurai wasp (Trissolcus japonicus), is not sold: Cornell's fact sheet answers "Commercially available? No." It is a tiny black parasitoid, 1–2 mm long, that lays its eggs inside stink bug eggs, usually attacking every egg in a mass, and in Asia it kills a large share of BMSB eggs — 60–90% according to StopBMSB, up to 80% according to Cornell and UC IPM. It reached the US on its own, was first found in Maryland in 2014, and NC State counts it in at least 13 states; some states rear and release it within their own borders, but deliberate movement between states has been restricted. It does not sting people. The way to help it is to avoid broad-spectrum sprays. Native natural enemies do less: StopBMSB reports that predators caused about 9–22% of egg mortality in crops, and native parasitoids only 1–4%. Katydids, ground beetles and earwigs eat the eggs, and StopBMSB lists the spined soldier bug among its native predators. Wheel bugs and praying mantises have been seen eating nymphs and adults.
Cultural controls
For the house, exclusion is the answer, and it has to be done before the bugs arrive in September. In the garden, physical barriers and hand-picking do more than sprays.
- Before September, caulk cracks and gaps, especially on the side of the house facing the sunset
- Fit tight window screens, seal round window air conditioners, and screen attic, foundation and chimney vents
- Weather-strip doors and fit working door sweeps
- Indoors, vacuum them up or drop them in soapy water — crushing them only worsens the smell
- Do not use foggers or insecticides indoors: they will not stop more coming in, and dead bugs feed carpet beetles
- In the garden, use row covers where possible, hand-pick into soapy water and crush pale green egg masses; leave dark grey or black ones, which are parasitised
- Keep pheromone traps well away from plants you want to protect
Chemical, last resort
- Insecticidal soapREI 12 h
- PyrethrinsREI 12 h
- BifenthrinREI 12 h
- Lambda-cyhalothrinREI 24 h
Sources
Penn State Extension, Brown Marmorated Stink Bug (revised 2017)
NC State Extension, Brown Marmorated Stink Bug (Walgenbach, revised 2022)
University of Maryland Extension, Tips for Dealing with Brown Marmorated Stink Bugs (2021)
University of Maryland Extension, Brown Marmorated Stink Bug (2024)
University of Maryland Extension, Stink Bugs on Vegetables (2023)
Virginia Tech VCE ENTO-173, Diagnosing Stink Bug Injury to Vegetables (Lopez & Kuhar, 2021)
UC IPM Home and Landscape, Brown Marmorated Stink Bug (Ingels & Varela, 2014)
StopBMSB.org (USDA SCRI), IPM for BMSB Part 3; Look-Alike Insects; Native Natural Enemies (2017)
StopBMSB.org, Samurai Wasp (Trissolcus japonicus) (2017)
Cornell NYSIPM, Samurai wasp (Trissolcus japonicus) fact sheet (Quinn & Nixon, 2021)
Utah State University Extension, The Samurai Wasp: New Hope in Fight Against BMSB
WSU Tree Fruit, Brown Marmorated Stink Bug (Beers & Marshall, 2017)
UC IPM, Relative Toxicities of Pesticides Used in Cucurbits to Natural Enemies (2016)
UC IPM Pest Management Guidelines: Cucurbits — Squash Bug, treatment table REIs (2016)
Penn State Extension, Spotted Lanternfly Management in Vineyards, insecticide table (2025)
Simaz et al., Environmental Entomology 52:998–1007 (2023), Trissolcus japonicus releases in Michigan
Texas A&M Field Guide to Common Texas Insects, Spined Soldier Bug
UNH Extension, Boxelder Bug fact sheet
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
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