Stink bugs are a significant and destructive invasive pest. The most commonly encountered species, the Brown Marmorated Stink Bug (BMSB), is native to East Asia (China, Japan, and Korea) and was first documented in the United States in the late 1990s. Because it is invasive, the BMSB lacks natural predators in its new environment, allowing populations to grow rapidly and cause widespread problems. The insect’s common name comes from its defense mechanism: the controlled release of a pungent, foul-smelling odor when threatened or crushed.
Defining the Stink Bug as a Pest
Stink bugs are classified as true bugs in the order Hemiptera, characterized by specialized mouthparts designed for feeding on fluids. Both nymph and adult stages possess a rigid, needle-like proboscis, or stylets, which they use to pierce plant tissue. This piercing-sucking feeding habit is the fundamental mechanism that classifies them as an agricultural pest. They are herbivorous insects that primarily extract juices from various parts of a plant, including leaves, stems, and fruit.
These shield-shaped insects are also defined by the noxious chemical compounds they release when agitated. This defensive cocktail is produced in specialized glands located on the underside of their body. The odor is often described as smelling like burnt tires or musty cilantro, caused by the aldehydes trans-2-decenal and trans-2-octenal. This foul scent serves as a warning to potential predators and is the primary reason they are considered a nuisance to humans.
Agricultural Damage and Economic Impact
The BMSB is a highly destructive pest because it feeds on a vast array of high-value crops, posing a threat to commercial agriculture. Its wide host range includes fruits, vegetables, and row crops such as apples, peaches, corn, soybeans, and tomatoes. Damage occurs when the bug inserts its proboscis into the plant, injects digestive enzymes, and then sucks out the liquefied plant material.
On developing stone fruits like peaches and nectarines, early-season feeding causes “cat-facing.” This results in a distorted fruit shape with sunken, corky areas on the surface. On pome fruits like apples, feeding leaves discolored depressions on the skin and irregular necrotic spots in the flesh beneath the surface.
This feeding damage directly affects the marketability of the produce. Internal damage to the fruit’s flesh makes the product unsalable, leading to significant economic losses for farmers. The defensive compound can also taint the flavor of certain crops, such as grapes destined for juice or wine production. The BMSB’s ability to spread aggressively and feed throughout the growing season compounds the economic threat.
Stink Bugs as Household Invaders
Stink bugs invade homes due to their biological need to survive the winter. As autumn temperatures drop, the insects seek a sheltered location to enter a dormant state called diapause. They are not attracted to indoor food sources, but rather to the warmth and protection a human dwelling provides from the cold.
They are attracted to sunny, south-facing walls in the late afternoon, which radiate heat and serve as a beacon for overwintering sites. Their flat, shield-shaped bodies allow them to squeeze through surprisingly small exterior openings. Common entry points include cracks around window and door frames, utility pipes, vents, and gaps behind fascia boards.
Once inside, they move into wall voids, attics, and crawl spaces, often clustering together. They typically emerge during warm spells in the winter or upon the return of spring, which is when homeowners notice them. If removal is necessary, avoid crushing them to prevent the release of the lingering odor, which can stain fabrics. A preferred method is to gently sweep them into a container or use a vacuum fitted with a stocking to contain the insects before disposal outside.
Safety Concerns for People and Pets
Despite their alarming appearance and defensive odor, stink bugs do not pose a physical danger to people or household pets. They are incapable of biting or stinging humans, as their mouthparts are designed solely for piercing plant material. Stink bugs are also not known to transmit any diseases to humans.
The strong odor they release is non-toxic and does not contain venom or poison that can cause serious harm. However, direct contact with the defensive fluid may cause mild, localized skin irritation or allergic symptoms, such as a runny nose or itchy eyes, in highly sensitive individuals.
For pets, the risk is minimal, as the foul taste of the bug’s defense secretions generally discourages consumption. If a pet consumes a small number of stink bugs, the worst outcome is usually mild digestive upset, such as excessive drooling or vomiting. While the insects are not poisonous, consuming a very large quantity could potentially cause a mass in the stomach, necessitating veterinary attention.