integrated pest management

Asian Lady Beetle
Harmonia axyridis

The multicolored Asian lady beetle, Harmonia axyridis, a native of Asia was introduced into the southeastern and southwestern portions of USA to deal with aphids on pecan trees. However, it spread rapidly to other portions of the US. It is a tree-dwelling lady beetle, more so than the native species of lady beetles, and a very efficient predator of aphids and scales. During the fall and early winter when the weather is cooler, the multicolored Asian lady beetle starts congregating on the south side of buildings and enters homes. The beetle does this because in their homeland of China they inhabit tall cliffs to overwinter. There are very few tall cliffs in Illinois, so the next best thing is a building.

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Spotted Lady Beetle Adult
Figure 1. Spotted Lady Beetle Adult

The multicolored Asian lady beetle can be easily distinguished from other species of lady beetles by the presence of a pair of white, oval markings directly behind the head, which forms a black M-shaped pattern. Adults are 1/4 inch long, 3/16 inch wide and yellow to dark-orange colored. In addition, their body is usually covered with 19 black spots. Adults can live up to 3 years. Female beetles lay yellow, oval-shaped eggs in clusters on the underside of leaves. The eggs hatch into larvae that are red-orange and black in color, and shaped like an alligator. The larvae are primarily found on plants feeding on soft-bodied insects such as aphids and scales. They eventually enter a pupal stage. The pupae can be seen attached to plant leaves. The adults emerge from the pupae and start feeding on aphids. The adults can be found on a wide-variety of trees including apple, maple, oak, pine, and poplar. There can be multiple generations per year.

The multicolored Asian lady beetle is a nuisance pest because the adults tend to congregate and overwinter inside buildings in large numbers. The beetles release a pheromone that attracts more beetles to the same area. Although it may bite, it does not injure humans nor can it breed or reproduce indoors. They are attracted to lights and light-colored buildings, especially the south side where it is warm. They then work their way into buildings through cracks and crevices. Dark colored buildings generally have fewer problems with beetles. Adult beetles will feed on ripening fruit such as peaches and apples, creating shallow holes in the fruit. Large numbers of beetles feeding on fruit may cause enough injury that it is less appealing for consumption.

Beetles can be prevented from entering homes by caulking or sealing cracks and crevices. Beetles already in homes can be physically removed by sweeping them or vacuuming. Be sure to empty the vacuum bags afterward. Do not kill the beetles. Just release them outdoors underneath a shrub or tree away from the house. Commercially available indoor light traps can be used to deal with beetles indoors. The traps need to be placed near the center of a room and they are only effective at night in the absence of competing light. In addition, they work best when room temperatures are 75°F or higher. If crushed, the beetles will emit a foul odor and leave a stain. The dust produced from an accumulation of dead multicolored Asian lady beetles behind wall voids may trigger allergies or asthma in people. Insecticides are not recommended for use indoors. Homeowners that want to avoid dealing with overwintering beetles entering their homes can hire a professional pest control company to treat the points of entry on the building exterior with a pyrethoid insecticide. The treatments need to be made in late September or early October before the beetles enter the building to overwinter. Beetles that are feeding on fruit can be controlled with a commonly used fruit insecticide. The beetle has been able to spread rapidly throughout portions of the USA because it was introduced into the country without its native natural enemies. However, populations may decline as cosmopolitan natural enemies start attacking them. For example, studies in North Carolina have demonstrated that up to 25% of the beetle populations are being parasitzed by a tachinid fly.

Prepared by Raymond A. Cloyd, Department of Natural Resources and Environmental Sciences, University of Illinois, Urbana, Illinois, in cooperation with the Illinois Natural History Survey. For additional copies, contact your local University of Illinois Extension Office.