The story below is an excerpt from our November/December 2017 issue. For the rest of this story and more like it subscribe today, log in to read our digital edition or download our FREE iOS app. Thank you!
Why do Asian lady beetles invade Blue Ridge homes in winter?
If pesky swarms of black-spotted, orange insects are invading your home, like they do every year, take heart, says Lee Townsend, extension entomologist at the University of Kentucky. It won’t always be like this.
“When they first show up, the first few years they’re around, they tend to just be out of control in overwhelming numbers,” Townsend says of the Asian lady beetles that appear in droves in late fall and winter. “Then things tend to settle down. You’ll see a few, but not the massive infestations.”
A native of Asia, the hardy bug with few natural enemies presumably hitched a ride on a Japanese freighter that docked at a Louisiana port in the 1960s. Coincidentally, pest control experts were already releasing them in Georgia, South Carolina and other states to get rid of insects that were damaging pecan groves and apple orchards. The first attempts were unsuccessful, but the Asian lady beetles were soon chomping their way through the Southeast and beyond.
“It likes forested areas, and the Blue Ridge region is forested,” says Townsend. “So it’s just an ideal habitat for the Asian lady beetle to thrive.”
By the 1990s, the ladybugs had spread like kudzu, taking over as both a beneficial import and an annoyance. “It’s got kind of a split personality in terms of being very helpful for some things but a nuisance in the fall,” Townsend says. “And that basically has to do with its behavior for spending the winter.”
All adult lady beetles overwinter in large clusters, with most indigenous species gathering at the base of trees where they’re not readily noticed. The Asian type, on the other hand, is visually attracted to vertical surfaces and contrasting colors. “So a light-colored house on a hill, surrounded by woods, is ideal for them,” says Townsend.
Once they land on a building, the insects crawl into cracks and crevices around window frames, doorways or exterior attic entrances. They are most active in late afternoon, when the temperature is warmest and the sun hits the structure’s surface from the west and south.
“For us [in Kentucky], it’s around Halloween when we tend to see the beetles really start to fly to their wintering sites,” says Townsend.
Asian lady beetles pose several problems. They can reproduce more quickly than the native red species, outcompete them for food sources, and in some cases, even kill them. The same needle-sharp mouth parts that puncture and eat aphids can also nip humans, who can develop asthma-like reactions to the defensive chemical the bugs produce. The odor itself, which the beetles emit from their leg joints to ward off danger and guide each other—a mass of ladybugs is less likely to become prey for mice or other animals—isn’t pleasant.
Then there’s the sheer downside of having bugs inside your humble abode.
“It’s not a good thing to have hundreds or thousands of those beetles crawling around in your house during the winter,” Townsend points out. And if they’re hunkered down in baseboards, walls and suspended ceilings during the cold-weather months, they’ll surface again once spring arrives when they try to escape to the outdoors.
Still, the beetles do what they were originally brought here to do: eat a lot of bad bugs, especially soft-bodied insects that can devastate trees, shrubs and crops. “The benefits,” Townsend notes, “are in the several hundred aphids that each one of these beetles eats as it grows up from egg to adult.”
If They’re Bugging You...
To keep Asian lady beetles from taking over your house this winter:
• Deal with them outside. Spray accumulations of beetles with insecticidal soap. “You’re way behind in the battle if you’re trying to fight them inside,” says Lee Townsend, extension entomologist at the University of Kentucky.
• Block obvious pathways. Install screens on attic ventilation openings, make sure door sweeps fit tightly, and caulk around windows. “The kinds of things that you would do to prevent heat loss and make your home energy-efficient in the winter,” Townsend says, “are going to be the same kinds of things that will help keep the insects out.”
• Vacuum them up and release them outdoors or dispose of the bag. Otherwise, they might survive and crawl out later.
• Don’t overreact with bug bombs and other interior pest control methods.
• Maintain your perspective. “We can reduce numbers but we can’t eliminate them because we’re trying to protect a small island from an ocean of production with the beetles,” Townsend says. “Hopefully we get to where we reach some sort of peace or balance with them.”