UNIVERSITY PARK, Pa. -- As the weather warms, many Pennsylvanians are experiencing an onslaught of foreign insect invaders -- Asian lady beetles. But despite the distress they may cause homeowners, these beetles provide a valuable service by reducing pest insect populations in crops, woodlands and home landscapes.
"In the last several years, multicolored Asian lady beetles have caused quite a stir," says Steven Jacobs, extension entomologist in Penn State's College of Agricultural Sciences. "Although they can be a nuisance, they do far more good than harm."
A native of eastern Asia, the beetle was introduced into the United States by the U.S. Department of Agriculture as a biological control agent. The tree-dwelling insect can live up to three years and is a voracious predator of aphids, scale insects and other pests.
Asian lady beetles originally were released in 1978 and 1981, but overwintering adults of the species first were observed in Pennsylvania in 1993. "Recent population increases probably did not result from those earlier USDA releases," Jacobs says. "The growth in numbers in Pennsylvania and other states is thought to be from a more recent accidental release of beetles from an Asian freighter in New Orleans. Contrary to some rumors, Penn State never has released Asian lady beetles into the environment."
At 9/32 of an inch long and 7/32 of an inch wide, these beetles are oval or convex and slightly larger than native lady beetles. They are yellow to red in color, with or without as many as 19 black spots on the wing covers. The head is usually concealed beneath a disk-shaped "collar," which is cream to yellow in color with a black 'M' design in the center.
Asian lady beetles become a nuisance when they invade homes in search of shelter and warmth. "Starting around the first of October, these insects will begin to congregate on windows, doors and porch decks, seeking sites to overwinter," says Jacobs.
"If they have entered your house, you may not notice them until temperatures begin to rise in the spring," he says. "After a few warm, sunny days, the beetles emerge from their hiding spots in search of an exit. This is not a new infestation -- they have been in your home all winter."
The presence of Asian lady beetles in large numbers can lead to near hysteria among some homeowners. Despite the nuisance the beetles can cause, they generally are harmless. They can bite, but they do not carry human diseases nor feed on wood, clothing or food. They also can exude a foul-smelling, yellow defensive chemical, which sometimes will cause spotting on walls and other surfaces.
Some people have reported allergic reactions to these defensive excretions. "Individuals who experience sinus irritations or mild skin irritations after encounters with Asian lady beetles probably should wash hands or other skin after contacting the insects," advises Jacobs. "In one controlled study, allergic reactions subsided with the removal of beetles from the home."
Mechanical exclusion seems to be the best way to keep them out of your house, says Jacobs. "Seal cracks and openings around windows, doors, siding, utility pipes and chimneys with silicone or silicone-latex caulk. Repair or replace damaged screens. Cover attic vents and fireplace chimneys with number 20 or smaller screen mesh.
"If beetles are already in your house, use a broom and dust pan or vacuum cleaner to remove them," Jacobs says. "But because they're very beneficial in controlling damaging pests, they should be released unharmed in a protected area outside."
For a free fact sheet on multicolored Asian lady beetles, contact the Penn State Cooperative Extension office in your county or visit the Web at http://www.ento.psu.edu/extension/factsheets/multc_asian_ladybeetle.htm.
###
EDITORS: Steven Jacobs can be reached at 814-863-3963 or sbj2@psu.edu.
Contact: Chuck Gill cdg5@psu.edu 814-863-2713 814-865-1068 fax