Have you had ladybugs seeking shelter in your home this fall and winter? They’re probably not our native, garden-friendly ladybugs, but Asian ladybugs. And unlike our native ladybugs, which tend to be more solitary and die off in the fall and winter, these “Asian ladies” like to gather in groups and overwinter in sheltered areas, like the eaves or windowsills or even inside our homes. While both species are helpful to our gardens by eating aphids and other soft bodied insects like white flies and mites, of the two, we really ONLY want the native ladybugs.
Here’s why: The Asian lady beetles were imported into the U.S. in the early 20th century to devour garden pests. This means of insect control, although non-chemical, became quite dangerous to much of our native ladybug and other native insect populations. The Asian lady beetles seek out and destroy the larvae and eggs of other insects, including our garden-friendly beneficial ones. They also possess a parasitic fungus, to which they’re immune, but which can infect and ultimately kill any other insect which consumes them. Hence, the Asian ladybugs are aggressive predators to our native ladybugs.
Who are they? The insects we usually call “ladybugs” are also called “lady beetles”, “7spotted lady beetles” or in Britain, “ladybirds.” In this article our native ladybugs are classified as members of the Coccinellidae family. The Asian ladybug Harmonia axyridis is an imported species.
How to tell the difference: The Asian ladybugs tend to look more orange sometimes, have more black spots on their backs, have larger white cheeks and a white border around what may seem to be their mouths, and are usually seen in clusters. Some sources describe a white M shape on their heads. They also emit a yellowish residue as well as a foul odor when smashed, not unlike the odor of a stinkbug. The native ladybugs, sometimes called the 7 spotted lady beetle, tend to have fewer black spots and smaller white cheeks than the Asian ladybugs, are usually more reddish in color (although color is not always a distinguishing characteristic), and have more rounded, less pointed heads.
How to attract and retain the native lady beetles: It is possible to purchase the “good” lady beetles for release into our gardens from nature-friendly suppliers. However, some scientific sources report that because these insects have a tendency to disperse long distances in search of food and because they often do not lay eggs just after being released, this purchase route is not always an effective method of getting the good lady beetles into our gardens.
The preferred method, of course, involves more than a 1-stop purchase. Recognizing that lady beetles tend to constantly be searching for food, be vigilant during the growing season to attract these friendly ladybugs by providing nectar sources from shallow flowers such as alyssum, cosmos, coreopsis, dill, coriander, and fennel to name a few. Offer these and they will find you. (It also helps if you have an infestation of aphids, which they love.) The other obvious course also is to avoid use of insecticides in your yard or garden, which destroy the not only the destructive insects, but also the helpful ones, like ladybugs.
Watch for these critters in your home or garden and learn to tell the difference.
Linda Mobley, Headwaters Master Gardener, March 1, 2019 - Photo Credit: Plunkett’s Pest Control
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