The Brown Marmorated Stink Bug (Halyomorpha halys) is an invasive insect that has become a widespread nuisance and a significant agricultural pest. This species generates frequent public concern, as large numbers often enter human structures to escape cold weather. While the bug poses little direct physical threat to people, its danger lies in its economic impact on food production and its status as a pervasive household pest. This article details the characteristics of the bug, evaluates its potential harm to human health, and clarifies the serious damage it inflicts upon plants and crops.
Identifying the Brown Marmorated Stink Bug
The adult Brown Marmorated Stink Bug (BMSB) is readily recognizable by its unique “shield” shape and a size that typically ranges from 12 to 17 millimeters in length. Its body color is a mottled mixture of various shades of brown, dark red, and black, giving it the characteristic “marmorated” or marbled appearance. Key identification features include distinct white bands found on the antennae and alternating dark and light bands along the thin outer margin of the abdomen.
The life cycle begins with light green, barrel-shaped eggs laid in clutches of about 28 on the underside of host plant leaves. Nymphs hatch from these eggs and progress through five developmental stages, growing from tiny, dark-bodied insects with red eyes to larger instars that develop the white bands on their legs and antennae. As the weather cools in late summer and fall, adult bugs enter a dormant phase called diapause, seeking sheltered, protected sites to survive the winter. This overwintering behavior is the primary reason large numbers aggregate inside homes and other structures.
Assessing the Danger to Human Health
The Brown Marmorated Stink Bug does not bite, sting, or transmit any known diseases to humans or pets. The most common human health concern is the powerful, unpleasant odor the insect releases as a defensive mechanism when it feels threatened or is crushed. This odor is produced by a chemical cocktail of volatile aldehydes secreted from glands on the underside of the thorax.
While the bugs pose no toxic threat, their presence can trigger mild allergic reactions in sensitive individuals. Exposure to the aerosolized defensive chemicals can cause symptoms such as rhinitis (runny nose) or conjunctivitis (eye irritation). Direct contact with the bodily fluids of a crushed bug can rarely lead to contact dermatitis or irritant keratitis if the fluid is rubbed into the eyes. These health issues are generally minor and result from physically disturbing the insect rather than an active threat.
Damage to Agriculture and Ornamental Plants
The greatest danger posed by the BMSB is its destructive impact on agriculture, as it feeds on over 300 different species of plants. The bugs possess piercing-sucking mouthparts, which they use to penetrate plant tissue and extract sap, injecting digestive enzymes into the feeding site. Both nymphs and adults feed extensively on fruits, vegetables, and field crops throughout the growing season.
Damage to tree fruits, such as apples and peaches, often manifests as surface deformities referred to as “cat-facing,” pitting, or scarring, which renders the fruit unmarketable for fresh consumption. In high-value crops like corn and soybeans, the bugs pierce the protective husks and pods to feed directly on developing kernels and seeds. This feeding causes shriveled kernels in corn and the “stay-green” effect in soybeans, where damaged plants remain green late into the season. Severe infestations have led to significant economic losses, including a reported loss of $37 million in apple crops in the Mid-Atlantic region in 2010.
Strategies for Control and Prevention
The most effective strategy for managing BMSB in a residential setting is exclusion, preventing the bugs from entering structures in the first place. This involves sealing all potential entry points, such as repairing torn window and door screens and applying caulk to cracks around utility pipes and window frames. Weather stripping should be installed around exterior doors to eliminate small gaps that the insects can use to gain access.
Once the bugs are inside, non-chemical removal methods should be used to avoid triggering the defense secretions. Vacuuming is an efficient method for removing large numbers of bugs from walls and ceilings; however, a stocking should be placed inside the vacuum tube to prevent the odor from permeating the machine’s canister. Manual removal can also be accomplished by sweeping the bugs into a container of soapy water, where they will drown without releasing their odor. Chemical treatments, typically involving synthetic pyrethroid insecticides, should be considered a measure of last resort and are best applied by a professional to the home’s exterior in the fall, before the overwintering period begins.