The grey stink bug most people encounter is a rough stink bug, a group of at least six species in the genus Brochymena native to North America. These mottled grey, shield-shaped insects are often found clinging to tree bark, where their coloring works as near-perfect camouflage. Unlike many of their plant-feeding relatives, rough stink bugs are primarily predators that eat other insects, making them largely beneficial in gardens and landscapes.
How to Identify a Grey Stink Bug
Adults are shield-shaped and measure roughly half to three-quarters of an inch long (11 to 18 mm). Their coloring is a mottled mix of grey, brown, black, and white, sometimes with faint orange or yellow markings. Like all stink bugs, they have a large triangular plate on their back that covers the front portion of the abdomen.
A few features set rough stink bugs apart from other stink bug species. Look for two white bands on the hind legs and no banding on the antennae. Their face comes to small points, and the front edge of the “shoulders” (the thorax, just behind the head) has a rough, toothed margin you can see under close inspection. That jagged shoulder edge is where the common name “rough stink bug” comes from. The two most frequently encountered species are Brochymena affinis and Brochymena sulcata.
Grey Stink Bugs vs. Brown Marmorated Stink Bugs
If a grey or brownish stink bug is entering your home in fall, there’s a good chance it’s actually the brown marmorated stink bug, an invasive species that looks somewhat similar but behaves very differently. Brown marmorated stink bugs have alternating light and dark bands on their antennae, which rough stink bugs lack. Brown marmorated stink bugs are also serious agricultural pests that feed on dozens of fruit and vegetable crops, while rough stink bugs are beneficial predators that only occasionally nibble on leaves.
Brown marmorated stink bugs begin moving toward buildings by mid-September, and the heaviest influx into homes typically happens from late September through mid-October. Rough stink bugs, by contrast, tend to overwinter under bark rather than inside houses. Checking the antennae is the fastest way to tell the two apart.
What They Eat
Rough stink bugs are beneficial predators. They feed on caterpillars, beetle larvae, and other soft-bodied insects, which makes them allies in gardens and orchards. They may occasionally feed on leaves, but damage to ornamental and garden plants from rough stink bugs is typically negligible.
Other stink bug species that share a similar grey or brown coloring are far more destructive. Plant-feeding stink bugs pierce fruit, vegetables, and nuts with straw-like mouthparts, leaving behind dark pinpricks, pitting, and discolored patches. On tomatoes, feeding spots appear as dark pinpricks surrounded by an area that stays green or turns yellow instead of ripening normally. On stone fruits like peaches, damaged tissue turns brown and corky. The flesh beneath feeding spots on apples and pears becomes pithy, white, and firm rather than developing its normal texture. Seedlings and leafy greens can develop a tattered look after heavy feeding. If you’re seeing that kind of damage, the culprit is likely a plant-feeding species rather than a grey rough stink bug.
Are They Harmful to People or Pets?
Grey stink bugs do not bite and pose no direct health risk to humans. Their primary defense is the foul-smelling chemical they release from glands on their underside when threatened or crushed, which is where the “stink bug” name originates. The odor is unpleasant but harmless.
For pets, stink bugs aren’t poisonous, but the secretions can irritate a dog’s or cat’s mouth and digestive tract. If your pet chews on or eats one, you may notice drooling, vomiting, or irritation of the tongue, gums, and lips. These effects are short-lived, and there don’t appear to be serious long-term health consequences.
Keeping Stink Bugs Out of Your Home
Because rough stink bugs prefer tree bark for overwintering, they’re less likely than brown marmorated stink bugs to invade homes. Still, any stink bug species can wander indoors through gaps in window screens, door sweeps, utility penetrations, and siding. Sealing these entry points before fall is the most effective prevention step. Caulk cracks around windows and doors, repair torn screens, and check where pipes and wires enter the house.
If stink bugs do get inside, the simplest removal method is a vacuum cleaner. Use a bag you can discard immediately, since crushed bugs will release their signature odor inside the vacuum. Avoid swatting them against walls or fabric for the same reason.
Managing Stink Bugs in the Garden
Since grey rough stink bugs are predators, they generally don’t need to be controlled in garden settings. They’re helping you by eating pest insects. If you’re dealing with a plant-feeding stink bug species instead, a few practical approaches work well.
Hand-picking is most effective in the morning, when stink bugs are sluggish. They have a habit of dropping off plants when approached, so hold a container of soapy water beneath them and tap the plant. Because stink bugs are mobile fliers, they’ll reinvade from surrounding areas, so hand-picking works best as a routine rather than a one-time effort.
Woven row covers or fine netting placed over susceptible crops like tomatoes and peppers can physically block stink bugs from reaching fruit. These barriers need to go on before fruiting begins, with edges sealed tightly against the ground. Chemical control is generally a last resort for home gardens because it limits harvest timing and can harm pollinators and the beneficial insects (including rough stink bugs) that help keep pest populations in check.