Large numbers of lady beetles (ladybugs) infesting homes and buildings in the United States were first reported in the early 1990s. Ladybugs normally are considered beneficial since they live outdoors and feed on plant pests.
One species of lady beetle, Harmonia axyridis, can be a nuisance however, when they fly to buildings in search of overwintering sites and end up indoors. Once inside they crawl about on windows, walls, attics, etc., often emitting a noxious odor and yellowish staining fluid before dying.
In many areas of the U.S., these autumn invasions are such a nuisance that they affect quality of life.
How To Get Rid Of An Infestation
The Asian Lady Beetle, Harmonia axyridis (Pallas), is relatively new to this country. The beetle is native to Asia (e.g., China, Russia, Korea, Japan), where it dwells in trees and fields, preying on aphids and scale insects. The first field populations in the United States were found in Louisiana in 1988. Since then the beetle has expanded its range to include much of the U.S. and parts of Canada.
During the 1960s to 1990s, the U.S. Department of Agriculture attempted to establish the Asian lady beetle to control agricultural pests, especially of pecans and apples. Large numbers of the beetles were released in several states including Georgia, South Carolina, Louisiana, Mississippi, California, Washington, Pennsylvania, Connecticut and Maryland. Some scientists believe that current infestations in the U.S. originated not from these intentional releases, but from beetles accidentally transported into New Orleans on a freighter from Japan.
Once the beetles are indoors, the easiest way to remove them is with a vacuum cleaner. If you later wish to release the beetles outdoors, place a handkerchief between the vacuum hose and the dust collection bag to act as a trap. A broom can also be used, but is more likely to result in staining when beetles emit their yellowish defensive secretion.
Sealing Entry Points
Sealing cracks and openings is the most permanent way of preventing lady beetles from entering buildings. The time to do this is in late spring or summer, before the adults begin flying to buildings in search of overwintering sites. Cracks should be sealed around windows, doors, soffits, fascia boards, utility pipes and wires, etc. with caulk or other suitable sealant.
Larger holes can be plugged with cement, urethane foam or copper mesh. Repair damaged window screens and install screening behind attic vents, which are common entry points for the beetles. Install tight-fitting door sweeps or thresholds at the base of all exterior entry doors. Gaps of 1/8" or less will permit entry of lady beetles and other insects. Gaps under sliding glass doors can be sealed with foam weather stripping. These practices will also help prevent entry of flies, wasps, crickets, spiders and other pests. Some householders may find it more practical to hire a pest control firm, building contractor or painter to perform these services.
Indoor Treatment - Insecticide foggers, "bug bombs" or sprays are generally not recommended for eliminating beetles indoors. Insecticides applied indoors for lady beetles tend to be ineffective and may stain or leave unwanted residues on walls, countertops and other surfaces. A vacuum is more sanitary and effective. Attempting to kill beetles hibernating in wall cavities and other protected locations is seldom effective. A better approach is to take preventive measures to reduce beetle entry in subsequent years.
Exterior Barrier Treatment - While sealing cracks and openings is a more permanent way to limit beetle entry, the approach is time-consuming and sometimes impractical. There can be countless cracks associated with eaves, siding, vents, etc. where insects can enter. On multi-story buildings, sealing becomes even more difficult.
If lady beetles are a perennial problem, owners may want to hire a professional pest control firm. Many companies apply insecticides to building exteriors in the fall, which helps prevent pest entry. Fast-acting residual insecticides can be sprayed in a targeted band around windows, doors, eaves, soffits, attic vents, and other likely points of entry.
To be effective, barrier treatments should be applied before the beetles enter buildings to overwinter. In Massachusetts, the proper timing for such treatments is typically late-September to early October although this will vary with seasonal conditions. During late winter or early spring, barrier treatments are ineffective since the beetles gained entry the previous autumn.
Other approaches have been suggested to alleviate problems with Asian lady beetles. Ladybug "houses" sold in garden supply catalogs will have no effect in keeping the beetles out of your home. Light traps can be useful for capturing flies and lady beetles in dark confined spaces such as attics, but will capture relatively few beetles entering living spaces in the fall or emerging from hidden locations the following spring.
Unfortunately, there is no "quick fix" or easy answer to annual lady beetle invasions. Vacuuming, pest proofing and properly timed exterior insecticide treatments can provide relief but will not prevent entry of every single beetle.