There are several thousand species of ladybugs, also known as ladybeetles or ladybirds. Most are considered to be beneficial insects, eating pesty aphids, mealybugs, thrips, leafhoppers and mites. But some ladybugs are also pests, eating cultivated plants, invading homes, emitting stinky secretions, and even biting.
While there are 400 native species of ladybugs in the Americas, the Asian ladybug was imported by the millions in the 1970s and 1980s to control aphids on soybean crops in southern states. They have been spreading west ever since. And yes, the ladybug invading homes is the Asian ladybug.
Home Invasions and How To Stop Them
In Asia, the native ladybugs overwinter in cracks in cliffs. Since there are more houses than cliffs in the United States, they think that a house is a good place to spend the winter. They find a crack under the siding or along a window frame. As more come, they leave more pheromone scent, which attracts even more beetles. Sometimes the crack leads all the way into the house and they find their way indoors.
Vacuuming them up is the easiest way to dispose of them. If they are on the house walls outside, you can spray them with an insecticidal soap to kill them.
The one possible benefit to having this problem is that it identifies that your house has a leak that lets in outside air. Caulking the leaky spot stops the beetles and may lower your energy bill.
American Ladybugs vs. Asian Ladybugs and other pests
The biggest problem with Asian ladybugs is they are thriving while some native populations of ladybugs are declining to the point of extinction.
Insects overwinter in different ways, some as eggs, some as larvae. Ladybugs spend the winter as adults. They get together in large groups, using their own body heat to stay warm. Native ladybugs prefer piles of mulch, hollow trees and logs. Some gardeners put up ladybug houses in sheltered locations in hopes of attracting native ladybugs to their gardens.
Having ladybugs spend the winter in your garden means an earlier start on getting rid of bad bugs next spring.
Many of the native, beneficial ladybugs are bright, stop-sign red in color with black spots. But they are also yellow, gray, and black -- with or without spots. Asian ladybugs are orange to orange-red in color.
If the ladybugs have stripes, they are probably Colorado potato beetles and are also considered a pest. The adult and larvae of Colorado potato beetles are voracious eaters of tomato, potato, eggplant and petunia plants.
Green ladybugs are not ladybugs at all, but adults of northern corn rootworm or cucumber beetles. Both are serious pests.
Native ladybugs can be picked up by hand and will not bite or cause a stink. Asian ladybugs can secrete a yellow liquid that does stain and stink.
Source: Jeff Rugg, University of Illinois Extension horticulture educator
