Marion Barnes – Senior County Extension Agent
Multicolored Asian Lady Beetles, aka “ladybugs” often invade our homes in search of a spot to ride out the winter months. In the fall these multicolored beetles may congregate on the sunny side of buildings, often by the thousands. These insects were first introduced by the U.S. Department of Agriculture into California in 1916 and other areas of the United States and Canada on several occasions (1978 through 1982) as beneficial insects for the control of the pecan aphid. Some scientists believe the current infestations in the United States originated not from these intentional releases, but from beetles accidentally introduced from Japan. Adult Asian ladybug beetles are oval-shaped, convex, and about one-fourth of an inch long and three sixteenth inches in width. Their color varies from orange to tan, to red, often with several black spots on their wings. On some Asian ladybug beetles, the spots may be indistinct or missing. Females tend to be multi-spotted, with males having few or no spots at all. A small, dark “M” or “W”- shaped marking can be found on the whitish area behind the beetle’s head. Asian ladybug beetles have four distinct life stages: egg, larva, pupa, and adult. Adult ladybug beetle begins laying eggs, usually found on the underside of leaves of host plants in the early spring. Eggs hatch in about three to five days and the larvae begin searching for aphids or other soft-bodied prey. Larvae and adults can consume hundreds of aphids a day and are considered beneficial insects. Larvae molt (replacement of an outer skin or exoskeleton) four times before entering a pupal stage after the last molt. At the end of the pupal stage, the adult beetle emerges from the pupa case. Depending on temperature and availability of food, development time from egg to adult generally requires about fifteen to twenty-five days. The multi-colored Asian lady beetle has become a problem in some areas of the United States. The tendency to congregate in large numbers and overwinter in buildings and homes make them a nuisance. Beetle flights are heaviest on sunny days following a period of cooler weather, when temperatures return to the mid-sixties. In the fall, most flight activity occurs during the afternoon and varies in intensity from day today. These beetles are classified as “ reflex bleeders”. When handled or disturbed they emit an odorous red to yellowish fluid from the joints of legs as a defensive mechanism to discourage predators. But in the home, the fluid may stain walls and fabric.
Studies indicate that Asian lady beetles are attracted to illuminated surfaces where they tend to congregate on sides buildings illuminated by the sun. Beetles seem to be attracted to contrasting light-dark features such as dark shutters on a light background or light shutters on a dark background. House color or construction (brick, concrete, wood/ vinyl siding) was less of a factor for attraction than surface contrast. Dwellings near fields or woods are especially prone to infestations. Once beetles alight on buildings they will find cracks, crevices, and other protected areas to overwinter and often congregate in attics, wall cavities, and other locations. Cracks around windows and door frames, soffit, behind fascia boards, and vinyl siding are typical entry points. Structures in poor repair with many cracks and openings are most vulnerable. Once temperatures begin to warm in late winter or early spring, beetles attempt to escape outdoors and may end up inside the building or home. Since they are attracted to light they are often seen around windows and light fixtures. Impacts on humans are minimal, other than being a nuisance. Asian ladybug beetles do not reproduce indoors like fleas and cockroaches, so those emerging in the spring are the same individuals that entered the structure in the winter. Although these beetles do not transmit diseases, studies have indicated they may cause allergies in some individuals. Ladybug beetles have chewing mouthparts for eating other insects, so if they land on you their bite may feel like a pinprick. Prevention seems to be the best ladybug beetle control method. Sealing cracks, openings, and other entry points are the most permanent way to prevent these nuisance pests from entering a building. Gaps of one-eighth of an inch or less will permit the entry of ladybug beetles or other insects. Damaged screens on windows, doors, or attic vents should be repaired. Caulk or weatherstrip exterior cracks and other openings to prevent entry. Unfortunately, there is no “quick fix” or easy solution to the annual invasion of the Asian ladybug beetle.
For more information on the Asian ladybug beetle, check out the Clemson Extension Home and Garden Information Center fact sheet.
Information for this article was taken in part from Entomology Fact Sheet 416: Asian Lady Beetle Infestation of Structures by M.F. Potter, R. Bessin, and L. Townsend, Extension Entomologists, University of Kentucky College of Agriculture.
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