Everyone loves ladybugs, right? Well times have changed, and this beloved insect is causing some problems. Now we are not talking about all ladybugs – just one species in particular: the multicolored Asian lady beetle, Harmonia axyridis.
You can tell the multicolored Asian lady beetle apart from others by the “M” on the tops of their heads, as you can see in this close-up.
Photo Credit: ©2002 Buglady Consulting
In its larval stage, the multicolored Asian lady beetle is an active feeder, controlling many garden pests.
Photo Credit: ©2005 Buglady Consulting
When the multicolored Asian lady beetle, Harmonia axyridis, becomes irritated, it secrets a yellow liquid that can stain walls.
Photo Credit: ©2004 Buglady Consulting
The multicolored Asian lady beetle gets its name because the insects are “multicolored,” as you can see from this photo. They can be orange to red in color, and when it comes to spots, some do not have any while others have many markings. To ID them, you need to look for the “M” on the head.
Photo Credit: ©2002 Buglady Consulting
The multicolored Asian lady beetle was intentionally imported from Russia, Japan, Korea and elsewhere in Asia for release in the United States as part of a federal effort to naturally control insect pests in trees. With the first releases back in 1916 and 1960, the beetle did not establish. In the 1970s and the early 1980s, tens of thousands of these beetles were intentionally released by the USDA’s Agricultural Research Service (USDA-ARS) in an effort to control insect pests that injure trees. It’s believed these beetles didn’t establish either.
Then in 1988, some beetles were collected in the wild in Louisiana. Some scientists believe the current infestations aren’t the beetles that were released intentionally. They think these lady beetles were accidentally transported into the US from Japan. Since then, the beetle has expanded its range to include much of the US and parts of Canada.
What’s the problem with the lady beetle? In their native countries there isn’t a problem. These beetles overwinter on cliff faces and crevices. But here in the US, they have taken to our buildings to overwinter. The multicolored Asian lady beetles are attracted to light-colored houses, especially light-colored walls with a south or southwest exposure. They settle down into the dark cracks to spend the cold season. This means in the winter they are likely to crawl inside houses and become an annoyance to the human inhabitants.
Recent studies have shown that the beetles’ attraction isn’t strictly to white or light-colored homes. Rather, these beetles are drawn to strong vertical contrasts in a home’s structure that are made apparent in the late afternoon – when the beetles’ urge to migrate is strongest. Homes or structures with vertical columns, dark-colored shutters against a light-colored wall or strong vertical shadows all simulate the appearance of trees against a mountainside, which resembles the beetles’ natural hibernation destination in Asia.
Once in the walls, these lady beetles are more likely to become active on warm winter days. When they are in your home, multicolored Asian lady beetles don’t feed or breed, - just die. They don’t do structural damage or lay eggs indoors either. But when they come indoors, they’re hard to control, which makes prevention very important.
Multicolored Asian lady beetles have been reported to nibble or “bite” humans. They aren’t aggressive, but they may taste to seek moisture. These nibbles won’t cause health problems, but there have been reports of allergy issues when high levels of these beetles are in buildings.
To prevent these unwanted visitors in your home, caulk up cracks and other openings that allow the lady beetles into the walls. Inspect the outside of building from top to bottom, and screen or seal any openings small enough to admit the beetles. Don’t forget the roof lines. If they’re inside, they can be removed by vacuuming them up or by using an insect trap. You can buy these from pest control companies, but you can build your own, too. The USDA provides directions online. I have also heard of people putting bay leaves or basil in windowsills or stuffing cotton balls with camphor essential oil on them in the entry holes. People even use Bengay around windows to keep them from entering (Bengay has both camphor and menthol).
Before you go off thinking multicolored Asian lady beetles are bad, you need to know they do have some great qualities in the garden. They are very aggressive feeders as adults and larva, and they’ll help control pests in your yard. They feed on aphids, caterpillar eggs, mites and many other pests. So if you find them in your house, bring them to your garden where they can go to work for you.