Pest Profile: The Asian Ladybug

That time of year is here again… actually, it’s been that time of year for several weeks, but they just showed up in my apartment over the last weekend. Zipping around, bashing themselves into light fixtures, clinging to windows, and generally making a nuisance of themselves. If they land on you, they’ll bite without much provocation at all. Such an unexpected move from such a pretty little insect…

I speak of course, of the Asian Multicolored Ladybeetle. Outdoors, they are wonderful beneficial insects, both larva and adults feasting on thousands and thousands of aphids, scale insects, and a myriad of other garden pests. When the weather turns cold, however, they seek shelter and warmth, and the most convenient place to get those is inside your nice snug house. Left to their own devices outdoors, they will huddle and semi-hibernate in large masses, keeping each other warm. Inside the house, there is no need for that, since it’s nice and warm already, so they crawl all over everything, eventually starving to death on the windowsills.

The Asian ladybeetle was imported as early as 1916 to help control insect pests in orchards, and they have spread everywhere since then. There are several species of ladybeetle native to this country, the most common being the 7-spot ladybeetle. All species are voracious eaters, both as larva and adults. The larva is as a familiar sight in the garden as the adults are, small black and orange banded 6-legged insects, usually clinging to the undersides of leaves if they are not attacking aphids. Adults are up to 1/4 inch long, ranging in color from pale yellow-orange to dark red, with anywhere from zero to 19 brown or black spots on their backs.

They’ve got no place in the house, though. The best and least messy way to rid your home of these pests is to vacuum them away. Do not try to swat them or sweep them away, as they secrete a noxious odor and a yellowish fluid that will stain walls and fabrics. There are various traps on the market that can be effective as well. Planting shade trees to cool the south and west sides of the house will also make it less appealing to the beetles.

The most effective method of keeping them out of one’s home, of course, is to seal any entry points. Gaps in windows and outside doors as small as 1/8 inch will admit ladybugs and other insects. Sealing gaps, also has the added benefit of improving the winter heating and summer cooling efficiency of your home; if bugs can’t get in, warm or cool air can’t get out! The outside of the building can also be treated, before the invasion begins, but such treatments are generally not as effective as people would like.

The good news in all of this is that the imported pests are doing what we brought them in to do, and are not really destructive beyond that. They seem to co-exist peacefully with our native species, and have helped cut down on the amount of pesticides sprayed in orchards to combat aphids and other insects. They don’t carry diseases, and it is truly just a nuisance when they come indoors for the winter. They do not attack the house structure, furniture or fabrics. They don’t sting, and their bites are nothing more than annoying. If it means running the vacuum a little bit more often this time of year to keep the insects away from my garden in the summer, I suppose I can do a little bit more housework.