Brown Marmorated Stink Bug
A shield-shaped, mottled-brown invasive stink bug from East Asia that crowds into homes in fall to overwinter and releases a foul odor when disturbed, but does not bite, breed indoors, or damage the structure.
Key facts
| Scientific Name | Halyomorpha halys |
|---|---|
| Beneficial Status | none |
| Class | Insecta |
| Family | Pentatomidae |
| Genus | Halyomorpha |
| Kingdom | Animalia |
| Order | Hemiptera |
| Organism Type | insect |
| Pest Status | True |
| Phylum | Arthropoda |
| Professional Recommended | rarely — exclusion and vacuuming handle most home invasions |
| Protected Status | none |
| Risk Level | low |
| Species | Halyomorpha halys |
| Taxon Authority | (Stål, 1855) (ITIS TSN 915660) |
| Treatment Recommended | contextual |
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Occasional invader: harmless indoors but a heavy fall home-invader and a major crop pest. is-it-a-pest = yes; treatment = exclusion + vacuum, NOT indoor sprays; beneficial_status = none. Every health / legal / taxonomy claim is cited; bite/disease/allergy claims carry TWO sources. -->
Overview
The brown marmorated stink bug is a shield-shaped, marbled-brown invader that crowds into homes each autumn to overwinter — an uninvited houseguest that pays its rent in smell. It arrived by accident from East Asia and was first found in Allentown, Pennsylvania in 1998. Source: https://extension.psu.edu/brown-marmorated-stink-bug For homeowners it is a nuisance, not a hazard. Source: https://ipm.ucanr.edu/PMG/PESTNOTES/pn74169.html
Identification
Adults are roughly ½–⅝ inch long — sources give about 15 mm (≈⅝ in) up to around 17 mm — with the flattened, five-sided stink-bug shield shape in a mottled mix of browns. Source: https://ohioline.osu.edu/factsheet/ent-90 Source: https://extension.psu.edu/brown-marmorated-stink-bug The most reliable marks are the pale bands on the antennae and the alternating dark-and-light blocks along the exposed rim of the abdomen. Source: https://ask.ifas.ufl.edu/publication/IN623 Source: https://extension.umn.edu/yard-and-garden-insects/brown-marmorated-stink-bug The shoulder behind the head is smooth and rounded, not spined. Source: https://ipm.ucanr.edu/PMG/PESTNOTES/pn74169.html
Lookalikes
Native brown stink bugs are easily confused with it, so check the antennae and shoulders. The rough stink bugs (*Brochymena*) and the brown stink bug (*Euschistus servus*) lack its clean white antennal rings. Source: https://ask.ifas.ufl.edu/publication/IN623 The rough stink bug also has a jagged shoulder edge and a two-pointed head, where this species stays smooth-shouldered and blunt-headed. Source: https://ipm.ucanr.edu/PMG/PESTNOTES/pn74169.html
Biology
The pale green-to-blue eggs are about 1 mm across and are laid in clutches of about 28 on the undersides of host-plant leaves. Source: https://ask.ifas.ufl.edu/publication/IN623 Newly hatched nymphs have a dark head and thorax and a reddish-orange belly, then molt through several wingless stages, darkening and banding, before reaching the winged adult. Source: https://ask.ifas.ufl.edu/publication/IN623 Generations per year depend on climate: Ohio and Pennsylvania typically see one (a second in a warm year), while Florida sources note one to two, with several possible in hot regions; only adults overwinter, passing it dormant rather than breeding. Source: https://ohioline.osu.edu/factsheet/ent-90 Source: https://ask.ifas.ufl.edu/publication/IN623
Where Found
Outdoors it feeds on a wide range of tree fruit, vegetables, and field crops, leaving corky spots and puckered "catfacing" injury. Source: https://ask.ifas.ufl.edu/publication/IN623 Indoors it concentrates in sheltered gaps — wall voids and the spaces around windows, doors, outlets, and light fixtures. Source: https://cals.cornell.edu/new-york-state-integrated-pest-management/outreach-education/whats-bugging-you/brown-marmorated-stink-bug Since its 1998 Pennsylvania arrival it has spread across much of eastern and western North America. Source: https://extension.psu.edu/brown-marmorated-stink-bug
Seasonality
The invasion is a fall event. Adults move toward overwintering sites in early autumn — Ohio reports flights starting in early September and peaking in late September or early October — before slipping into shelter. Source: https://ohioline.osu.edu/factsheet/ent-90 Source: https://ipm.ucanr.edu/PMG/PESTNOTES/pn74169.html They emerge in spring — Ohio around early May, Pennsylvania late April to mid-May — then mate and lay eggs through summer. Source: https://ohioline.osu.edu/factsheet/ent-90 Source: https://extension.psu.edu/brown-marmorated-stink-bug
Signs
The clearest indoor sign is the bugs themselves: clusters of slow-moving adults on warm fall days, or on winter days when household heat rouses them. Source: https://extension.umn.edu/yard-and-garden-insects/brown-marmorated-stink-bug A pungent smell when one is squished or disturbed is a second giveaway, and in heavy numbers their excrement can stain surfaces. Source: https://entomology.umn.edu/brown-marmorated-stink-bug Source: https://ask.ifas.ufl.edu/publication/IN623
Risks
The risk to people is minimal. It does not bite or sting, draws no blood, and is not known to pass disease to people or pets. Source: https://ipm.ucanr.edu/PMG/PESTNOTES/pn74169.html Source: https://www.canr.msu.edu/news/managing_brown_marmorated_stink_bugs_in_homes It does no structural harm either — it neither chews nor bores into wood and will not reproduce indoors. Source: https://www.canr.msu.edu/news/managing_brown_marmorated_stink_bugs_in_homes Source: https://ipm.ucanr.edu/PMG/PESTNOTES/pn74169.html Some people react to the chemical it releases: Penn State notes allergy-type symptoms such as runny nose or eye irritation in sensitive people, and UMass reports a mild allergic reaction described by some Maryland orchard workers. Source: https://extension.psu.edu/brown-marmorated-stink-bug Source: https://www.umass.edu/agriculture-food-environment/greenhouse-floriculture/photos/brown-marmorated-stink-bug Crushing one against bare skin can also cause a localized dermatitis. Source: https://extension.psu.edu/brown-marmorated-stink-bug Source: https://cals.cornell.edu/new-york-state-integrated-pest-management/outreach-education/whats-bugging-you/brown-marmorated-stink-bug
Is It A Pest
Yes — on two fronts. In the home it is a nuisance pest that invades in large fall aggregations and stinks when handled, though it does no lasting harm. Source: https://ipm.ucanr.edu/PMG/PESTNOTES/pn74169.html On the farm it is a serious crop pest whose feeding deforms and ruins fruit and vegetables. Source: https://ask.ifas.ufl.edu/publication/IN623
Beneficial Notes
This species has no recognized beneficial role in North America. It is an invasive insect from East Asia that is both a household nuisance and a damaging crop pest, so its presence is not something to encourage. Source: https://ipm.ucanr.edu/PMG/PESTNOTES/pn74169.html Source: https://ask.ifas.ufl.edu/publication/IN623
When Not To Treat
Skip the spray can indoors. Once bugs are in the wall voids and living space, interior insecticides tend to be ineffective and can contaminate living areas. Source: https://ipm.ucanr.edu/PMG/PESTNOTES/pn74169.html Source: https://entomology.ces.ncsu.edu/faqs-brown-marmorated-stink-bug/ Timing matters too: NC State advises against sealing tight in fall or winter, which traps bugs inside — let overwintering adults leave in spring, then seal before the next fall return. Source: https://entomology.ces.ncsu.edu/faqs-brown-marmorated-stink-bug/
Prevention
Prevention is exclusion. Seal the gaps bugs use to get in — around windows, doors, siding, utility lines, and chimneys — with a quality silicone or silicone-latex caulk or foam sealant. Source: https://extension.psu.edu/brown-marmorated-stink-bug Source: https://ipm.ucanr.edu/PMG/PESTNOTES/pn74169.html Bugs that do get in are best vacuumed up and emptied into soapy water rather than squashed, avoiding both the smell and the staining. Source: https://extension.umn.edu/yard-and-garden-insects/brown-marmorated-stink-bug Source: https://entomology.ces.ncsu.edu/faqs-brown-marmorated-stink-bug/
Treatment
The program is exclusion and physical removal. Beyond exterior sealing, caulk the cracks and crevices around window and door trim, ceiling fixtures, and chimneys to confine bugs to the walls, and drown any found inside in soapy water. Source: https://ohioline.osu.edu/factsheet/ent-90 Source: https://entomology.ces.ncsu.edu/faqs-brown-marmorated-stink-bug/ Do not rely on interior sprays — extension programs report they are generally ineffective against this mobile, reinvading insect and are not recommended indoors. Source: https://ipm.ucanr.edu/PMG/PESTNOTES/pn74169.html Source: https://extension.umn.edu/yard-and-garden-insects/brown-marmorated-stink-bug
Inspection
Confirm the species first by its white antennal rings and smooth shoulder margin, which separate it from native rough and brown stink bugs. Source: https://ipm.ucanr.edu/PMG/PESTNOTES/pn74169.html Source: https://ask.ifas.ufl.edu/publication/IN623 Time inspections to the fall window — heavy clustering on warm building faces in September and October — and trace the active entry routes for sealing. Source: https://ohioline.osu.edu/factsheet/ent-90 Source: https://extension.psu.edu/brown-marmorated-stink-bug
Kids
The brown marmorated stink bug looks like a little brown shield with stripey antennae, and in fall it sneaks into houses for a warm winter nap — a tiny freeloader with a built-in stink alarm. Bump one and it puffs out a smell some say is like cilantro. Source: https://entomology.umn.edu/brown-marmorated-stink-bug The friendly part: it does not bite, sting, or make you sick. Source: https://ipm.ucanr.edu/PMG/PESTNOTES/pn74169.html So if you spot one, don't squish it — scoop it into a cup or let a grown-up vacuum it up. Source: https://extension.umn.edu/yard-and-garden-insects/brown-marmorated-stink-bug
Sources
How we know — institutions cited: Penn State, Minnesota, Florida/IFAS, Ohio State, UC IPM, Cornell NYS IPM, Michigan State, NC State, and UMass extension/IPM programs, with taxonomy from ITIS (*Halyomorpha halys* (Stål, 1855), TSN 915660). Safety-critical claims each carry two independent allowed sources. Review status: unreviewed (draft).
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