Lady beetles are back! You may have noticed congregations of lady beetles on the sides of your home or even inside porches or garages already this year. These are the 'Asian lady beetles' or, because of the time of year that they usually arrive, 'Halloween lady beetles'. Most everyone associates lady beetles with their beneficial aspects of controlling insect pests such as aphids and scale insects, however this particular species, Harmonia axyridis, has become a regular nuisance pest throughout the whole eastern half of the country in the last few years.
Asian lady beetles are particularly obnoxious because of their habit of congregating in homes during the fall to pass the winter. Some reports have been received of them biting/pinching and certainly smelling bad. One of the defensive tactics of these beetles is to emit a foul smelling substance when disturbed. When hundreds or thousands of these beetles are grouped together, that smell is greatly intensified and usually becomes the biggest objection of all.
During the summer months the Asian lady beetles are helpful because they feed on aphids in trees on other plants. During the late summer and fall time, they often fly to light colored homes, usually south west facing sides, where they look for corners, cracks or other 'protected nooks' to congregate in preparation for overwintering. Because they are attracted to light, some have suggested using a light trap inside the home to control them. The effectiveness of this method of control has not yet been determined and, because it is an expensive option, it is not recommended at this time.
The easiest way to dispose of beetles found inside the home is with a vacuum cleaner. A long extension will suck them from ceilings and light fixtures. I have found that most die after being sucked through the vacuum and the few that survive seldom are able to find their way back out. This indicates that removal of the bag after each episode may not be necessary. As a preventive measure, exterior cracks and other openings can be sealed during the spring or summer months. Use a good quality silicone or silicone-latex caulk to seal cracks around windows, doors, siding, fascia boards, utility pipes, and other potential entry points. Repair damaged window screens and install insect screening behind attic vents. Insecticides are not generally recommended, unless the temporary annoyance can no longer be tolerated. Aerosol-type foggers containing synergized pyrethrins can be used in attics, but will provide no residual control of beetles that will emerge from cracks and protected cavities during the spring months. Aerosol foggers or sprays are not recommended for treatment of bedrooms or other living areas within the home. The effect of such treatment would be negligible unless beetles are crawling on exposed surfaces, where they could just as easily be removed by vacuuming.
Those who do not wish to chance a recurring problem with overwintering lady beetles next season may apply Dursban or Diazinon to the exterior of the building in an effort to prevent them from getting in. Some homeowners may want to enlist the services of a knowledgeable pest control firm that can apply long-lasting/rapid-knockdown formulations of synthetic pyrethroids (e.g., Tempo, Demon, Commodore, Saga, Suspend) around eaves, attic vents, windows, siding, and other likely points of entry. In either case, the key is to apply the treatments in late September or early October, before pests enter buildings to overwinter. For more information on Asian lady beetles, refer to Purdue's Extension publication E-214, available on-line at http://www.agcom.purdue.edu/AgCom/Pubs/menu.htm or from your local county Cooperative Extension Service Office or by calling Purdue's toll-free Extension information line at 1-888-EXT-INFO (1-888-398-4636).
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The Plant & Pest Diagnostic Laboratory at Purdue University.