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Ladybug, Ladybug, Fly Away from My Home!

Author: Linda McCandless, Communication Services, NYSAES, Cornell University.

The invasion of the Halloween lady beetle has just begun. They're moving in for the winter after gorging on your aphids during the summer. They're found clustering in windowsills, winging about, and crunching underfoot! The little beetles are only 1/4 inch long and 3/16 inch wide, and they range in color from pale yellow-orange to brighter orange, with or without black spots on the wing covers.

"Homeowners should not worry," said Janet J. Knodel, entomologist with the NYS IPM Program at the Agricultural Experiment Station. "They may be here in record numbers, but multicolored Asian lady beetles don't sting, carry human disease or eat wood, clothing, food or houseplants." They have been reported to bite, but it is rare and harmless.

The spotted ladies are becoming somewhat of a major nuisance to homeowners because of their habit of invading houses and buildings in large numbers in the fall, and appearing again on warm, sunny days in February and March. Despite its annoyance value, H. axyridis preys upon many species of injurious soft-bodied insects such as aphids, scales, and psyllids, and is considered beneficial to growers and agriculturists.

Harmonia axyridis (Pallas) was first found in New York in Chemung County in early 1994. It was introduced as a biological control agent and is rapidly spreading through the Empire State and New England. An adult beetle is capable of eating 90 to 270 aphids per day, and each larva can consume 600 to 1,200 aphids during its development. In New York, these lady beetles have been prevalent on copper beech, honeysuckle, and European spindle trees heavily infested with aphids. They have been used in Connecticut for control of red pine scale, and have been observed feeding on the balsam twig aphid and pine bark adelgid in Christmas tree plantations and on aphid-infested apple, birch, cotoneaster, and rose, in Pennsylvania.

The native range of H. axyridis encompasses much of Asia. It was first released to control aphids on several agricultural crops in North America. Although the beetle was officially introduced by the USDA in California in 1916, 1964, and 1965, some researchers think the current lady beetle populations originated from accidental introduction of the species during freighter activity in New Orleans. Since the early 1990s, this exotic lady beetle has proliferated and moved rapidly from the Deep South into the Northeastern states and eastern Canada and is now widely distributed across much of the United States east of the Mississippi River. The beetle is also found on the West Coast.

In central New York, Knodel says the multicolored lady beetles are beginning to congregate by the hundreds on walls, doors, ceilings, and windows, as well as outside surfaces, especially on warm sunny days. They prefer the light-colored houses located in open fields, because they mimic the beetle's natural overwintering habitat - rock cliffs - in Asia.

Knodel does not recommend the use of insecticide for controlling populations of H. axyridis. The best technique for managing lady beetles is first to prevent their entry into houses and other buildings by sealing cracks and openings around windows, doors, siding, and utility pipes with a quality silicone or silicone-latex caulk. Similarly, repair door and window screens or other openings to the outdoors using regular window screening (about 18 X 16 mesh size). If beetles still gain entry into living spaces, Knodel recommended removing and disposing of them using a broom and dustpan, or vacuum cleaner, and releasing them outdoors. When using a broom and dustpan, gently collect the beetles to avoid alarming them. If alarmed, they may discharge a yellow fluid that can stain walls, paint, and fabrics, and that has an unpleasant odor.

Scientists predict that multicolored Asian lady beetle populations will become more balanced when its prey numbers decrease and Harmonia itself falls prey to native natural enemies. Its large, even explosive population is probably caused by the massive abundance of prey (predominantly aphids and scales), apparent lack of competition from native lady beetles, and apparent lack of native natural enemies.

For further information, see the fact sheet on the Multicolored Asian Lady Beetle, written by Janet J. Knodel, IPM, Geneva, NY, and E. Richard Hoebeke, of the Dept. of Entomology, at Cornell.

Other information available at: Biological Control: A Guide to Natural Enemies in North America and: Proceedings of the Cornell Community Biological Control Conference