The brown marmorated stink bug (Halyomorpha halys) is a familiar, unwelcome presence in many homes and agricultural areas. This insect is recognizable by its shield shape and mottled brown coloration, which provides camouflage. When disturbed, these bugs release a strong, unpleasant odor, a defense mechanism and the source of their common name. Their increasing numbers have made them a significant nuisance.
The Invasive Journey
The brown marmorated stink bug is not native to regions like North America and Europe, originating from East Asia (China, Japan, Korea). It was likely introduced accidentally through international trade, possibly as a stowaway in shipping crates or machinery. The first documented U.S. specimen was collected in Allentown, Pennsylvania, in 1998. In Europe, it is believed to have arrived around 1998, potentially via imported roof tiles into Switzerland.
Their rapid proliferation in new environments stems from the absence of natural predators and parasites. In native habitats, parasitic wasps like Trissolcus japonicus (the samurai wasp) control populations by laying eggs inside stink bug eggs. In invaded territories, these biological controls were initially missing, allowing populations to grow unchecked and become agricultural and nuisance pests. While some native predators are adapting, their impact has not controlled widespread populations.
Biological Keys to Their Success
Several biological characteristics contribute to the brown marmorated stink bug’s high population numbers. They have a high reproductive rate. Females can lay multiple batches of eggs throughout a season, typically from May through August. Each egg mass usually contains 20 to 30 barrel-shaped, light green eggs, often deposited on the underside of plant leaves. A single female can produce between 100 to 500 eggs in her lifetime, averaging 240, leading to rapid population growth.
They are also highly polyphagous, feeding on over 100 plant species. Their diet includes agricultural crops such as apples, peaches, corn, soybeans, tomatoes, and peppers, as well as ornamental plants and wild vegetation. This diverse diet ensures a constant food supply, allowing them to thrive across various landscapes. Their piercing-sucking mouthparts extract juices from plants, causing damage.
Brown marmorated stink bugs exhibit remarkable adaptability, flourishing in diverse environments and climates. They establish populations in temperate and, less frequently, tropical areas. Their hardiness allows them to withstand various conditions and resist common pest control methods. A recent study suggests climate change could expand their suitable U.S. habitat by 70%, potentially allowing them to move further north.
Seasonal Habits and Indoor Invasions
The brown marmorated stink bug’s most noticeable behavior is its tendency to invade homes and structures as temperatures drop. This is part of their overwintering strategy, seeking sheltered locations to enter a state of dormancy (diapause). As late summer and fall cool, they are drawn to warm, protected areas like building walls and interiors.
They gain entry into homes through small openings like cracks around windows, doors, utility pipes, or gaps in siding. Once inside, they do not feed or reproduce, but aggregate in hidden areas like attics or wall voids. Their attraction to light and warmth draws them towards sun-drenched walls and windows, facilitating entry. Aggregation pheromones released by a few bugs attract many more, leading to large indoor clusters. This annual indoor migration brings them into direct contact with humans, making their presence apparent.
Managing Stink Bug Encounters
Brown marmorated stink bugs are nuisance pests in residential settings due to their numbers and unpleasant odor when disturbed. They do not bite humans, spread diseases, or cause structural damage, but their presence can be alarming and their scent persistent. Beyond household nuisance, they inflict significant agricultural damage, impacting fruit, vegetable, and field crops. Their feeding causes cosmetic and internal damage to produce, leading to unmarketable crops and economic losses for farmers.
For homeowners, preventing entry into structures is the most effective management approach. Seal all potential entry points by caulking cracks around windows, doors, pipes, and siding. Repair or replace damaged window and door screens. Install tight-fitting sweeps under exterior doors to block access.
Once inside, non-chemical removal methods are recommended to avoid odor release or indoor pesticides. Vacuuming is effective; use a dedicated vacuum or a stocking over the hose to prevent odor permeation. Sweeping them into soapy water is another simple method, as they will drown. Avoiding outdoor lighting that attracts them and promptly disposing of garbage can also reduce their appeal.