The appearance of lady beetles indoors, particularly during cooler months, signals the presence of the Multicolored Asian Lady Beetle (Harmonia axyridis). While native ladybugs are welcomed in the garden for their appetite for pests like aphids, this invasive species becomes a significant household nuisance in the fall and winter. The Asian Lady Beetle aggregates on buildings seeking shelter for diapause, or winter dormancy, before entering wall voids and living spaces. This article provides practical steps for the immediate removal of these indoor invaders and outlines long-term structural prevention.
Distinguishing Nuisance Beetles from Beneficial Ones
The first step in control is correctly identifying the species, as native ladybugs should be left undisturbed outdoors. The Asian Lady Beetle is distinguishable by a prominent black marking shaped like an “M” or “W” directly behind its head on the white section called the pronotum. While their color varies widely from pale orange to deep red, this “M” marking is the most reliable identifier. Native ladybugs typically have a black head with smaller white markings on the sides.
The behavior of the Asian Lady Beetle makes it problematic once it enters a structure. They gather in large numbers, often on the sunnier, southwest-facing sides of buildings, before finding entry points. When disturbed or crushed, these beetles engage in reflex bleeding, secreting a yellowish fluid from their leg joints. This hemolymph fluid has a foul odor and can easily stain walls, fabrics, and carpets.
Non-Pesticide Methods for Immediate Indoor Removal
The most effective method for removing beetles already inside is using a vacuum cleaner, which avoids crushing them and triggering the release of staining hemolymph. To prevent the collected beetles from escaping and to protect the vacuum, a simple modification is recommended. Secure a nylon stocking or thin sock inside the vacuum hose attachment using a rubber band before starting suction.
This technique allows the beetles to be collected directly into the stocking, bypassing the vacuum bag or canister, which can retain odor. Once collection is complete, immediately remove the stocking, seal it closed with the rubber band or a knot, and dispose of it outdoors or in a sealed plastic bag. For smaller groups, gently sweep them into a dustpan or use paper to capture and release them outside, though this is less efficient for large numbers.
For beetles congregating in darker, enclosed spaces like attics, simple light traps can be used. These beetles are naturally attracted to light, and a trap can be constructed or purchased to draw them in without chemicals. Ensure the light trap is the only light source in the area to maximize its effectiveness.
Sealing Entry Points and Exterior Prevention
Long-term control focuses on exclusion, which involves sealing all potential entry points on the exterior of the home. This should be done in late summer or early fall before the beetles begin aggregating. Common entry points are small cracks and gaps around windows and door frames, which should be sealed with a high-quality silicone or silicone-latex caulk. Inspect all utility line entry points, such as those for cables or plumbing, and seal any openings around them.
Structural maintenance also involves ensuring all windows and vents are properly screened, and that any tears or holes in existing screens are repaired or replaced. Install door sweeps on all exterior doors to eliminate gaps along the threshold, a common access point for crawling insects. For larger structural gaps, like those beneath siding or in the foundation, use copper mesh or an appropriate sealant to plug the opening.
As a final preventative measure, an exterior barrier treatment using residual insecticides can be applied to the structure’s surface in late September or early October. These products, often containing synthetic pyrethroids like bifenthrin, deltamethrin, or cyfluthrin, create a chemical barrier that prevents the beetles from crawling inside. The insecticide should be applied to areas where beetles congregate, such as around windows, doors, eaves, and attic vents, but this treatment is ineffective once the insects are already inside for the winter.