Toward the end of the 20th century, homeowners noticed a new winter houseguest: the Asian lady beetle. Confusion arose because many of us assumed that this was our beloved native ladybug that had never expressed any desire to spend winter with us.
Like the native ladybug, the Asian lady beetle is a vast consumer of aphids, eating 90-270 aphids daily. Introduced by the U.S. Department of Agriculture’s Agricultural Research Service into this country in the 1970s and 1980s to decimate the pecan aphid, the Asian lady beetle today is the dominant species of ladybugs in North America. They have done their job well, nearly eliminating these harmful aphids.
The Asian lady beetle differs from our native ladybug in several ways. First, it is larger than our native species, with colors ranging from yellow to orange to red. Second, although it remains outside in its native habitat, the Asian lady beetle hibernates inside our houses during the winter whereas our native ladybug prefers to remain outside.
Typically, in North Carolina they will seek indoor shelter in November, thereby becoming something of a seasonal pest.
While they can produce multiple litters in a year, they will not lay eggs in our house while they are busy hibernating. They are most prolific during a cool and moist growing season, explaining why some winters we experience more guests than in others.
They are hibernating in an effort to conserve their food reserves and will not eat until they suddenly leave us in the spring.
What should you do if you find yourself inundated with Asian lady beetles? Don’t swat or crush them because they can emit a yellow body fluid that is quite smelly. During hibernation they aren’t breeding so you needn’t be concerned with offspring.
The best advice is to leave them alone if possible. They can bite, which can be an irritant. In my house they seem to settle in a kitchen window where they park themselves and simply sit throughout the winter.
If sharing your house with a group of uninvited guests isn’t your thing, you can vacuum them up — but remember, they are of great benefit in the garden as soon as spring arrives. They do not carry disease, nor do they eat building materials. All they want is a warm area to sleep away the winter.
How do they get in? They can squeeze through tiny cracks, cracks that are almost impossible to see. You can drive yourself crazy trying to find these cracks, but chances are they will outwit you. They love the warmth of overhead light fixtures so you’ll probably find yourself emptying them once the beetles have left.
Above all, please don’t resort to chemical measures in the house. Not only is their impact upon the beetles limited, few of us want to smell the chemical fumes in a house that’s tightly sealed for the winter. The best treatment is to wait them out, as they will leave once the outside temperature has risen.
And remember: The next time you reach for a pecan, you have the Asian lady beetle to thank.
Absent from their gardens, Kit and Lise enjoy roaming our region exploring the intersection of horticulture and suburban living. More on Instagram @AbsenteeGardener or email firstname.lastname@example.org.