The term “tree roach” is a common, non-scientific label used to describe large cockroach species that primarily live outdoors near trees and wood. These insects frequently seek refuge inside human dwellings, causing concern. Understanding their identity and outdoor habits is the first step toward effective management. This article clarifies the most common species and provides actionable steps to prevent entry.
Defining the “Tree Roach”
The insect most frequently identified as the “tree roach” is the Smoky Brown Cockroach, scientifically known as Periplaneta fuliginosa. This species is notably larger than many common indoor pests, typically measuring between 1.25 and 1.5 inches in length. They possess a uniform, deep mahogany or dark brown coloration, giving them a distinct, shiny appearance.
Both males and females have fully developed wings that extend slightly beyond the abdomen. This makes them one of the few domestic cockroach species capable of sustained flight, often gliding from trees or high places toward light sources at night. Their size and dark coloring are key characteristics that distinguish them from smaller, lighter species.
Natural Environment and Behavior
The Smoky Brown Cockroach is an outdoor species that requires a high-moisture environment to survive, as it is highly susceptible to desiccation. They thrive in warm, humid climates. The female deposits a dark brown egg case, or ootheca, in a hidden, sheltered spot.
These insects are primarily nocturnal detritivores, meaning they feed on decaying organic matter such as leaf litter, mulch, dead insects, and plant material. They congregate in damp, dark harborages close to human structures, including tree holes, under loose bark, in woodpiles, and within the organic debris found in clogged gutters and roof lines. Their preference for vertical locations explains their common nickname and their tendency to access buildings from above.
Preventing Indoor Intrusion
Tree roaches typically move indoors when their outdoor environment becomes unsuitable, often seeking shelter from extreme heat, drought, or cold weather. They are also strongly attracted to light, a phenomenon called positive phototaxis, which frequently draws them to illuminated doorways and windows at night. To stop their entry, exclusion and moisture reduction are the most effective strategies.
Exclusion
Exclusion involves creating a physical barrier to block all potential entry points into the structure. Use a high-quality silicone-based caulk or expandable foam to seal cracks and holes in the foundation and exterior walls. Pay close attention to gaps around utility lines, such as pipes, cables, and air conditioning units, where they penetrate the siding. Ensure that all doors and windows have tight-fitting weatherstripping and door sweeps, as a gap of just one-sixteenth of an inch is large enough for many insects.
Moisture Control and Habitat Removal
Address moisture sources outside by clearing clogged gutters and downspouts, which can serve as both a water source and an outdoor habitat. Trimming back tree limbs and shrubs that touch the house also removes a potential bridge the roaches use to access the roofline and upper story entry points.