The quintessential “good bug,” ladybugs (aka ladybird beetles) are the poster child of the beetle world. Everyone knows that ladybugs eat aphids and other “bad bugs” (especially scale insects) and should be welcomed in the garden.
Actually, not all ladybug species are red. Some species are orange, yellow, white, black, brown, or gray. And not all ladybug species eat aphids, although most do. Some are even agricultural pests, such as the infamous Mexican Bean Beetle. Still, most ladybugs are red, and they eat vast numbers of aphids, as well as scales, mealy bugs, leaf hoppers, mites and other soft-bodied insects and their eggs.
Every spring, our local garden center sells tubs of adult beetles that can be released at home in the garden. I started wondering where these thousands of ladybugs come from, and if they really lived up to their pest-eating reputation.
I learned that most of the ladybugs sold in the U.S. are harvested during the winter, when the adults congregate in huge masses in warm, sheltered spots such as the south side of a house or tree. There, they enter a kind of hibernation, called diapause, to wait out the cold weather. This makes collecting the bugs easy, as they can be scooped up by the hundreds.
The problem comes in the spring. As days lengthen, the adults wake up and disperse. That’s fine in the wild, but if you’ve just paid good money for a bucket ‘o bugs, you want them to linger in your garden, not take off for greener pastures.
As gardeners, our goal is to keep the adult beetles around long enough for them to lay eggs. Those eggs will hatch into larvae, and it’s the larvae that we really want. They don’t have wings, so they’ll hang around and do garden duty until they pupate and become adults. That process, from egg to adult, takes about two weeks.
A single ladybug larva will consume its weight in aphids every day. In the same time, an adult will eat approximately 50 aphids. The larvae aren’t nearly as cute, looking like a monster from a Tokyo sci-fi film, but I guarantee they’re much scarier if you’re an aphid.
The best way to delay the adult’s departure is to provide plenty of prey. In other words, you should have lots of aphids available for them to eat. On the other hand, if the pests get the upper hand, it can be very difficult to make any headway against them. As you can see, timing is tricky!
It takes a lot of self control to allow these sap-sucking pests to multiply in our gardens without reaching for the spray can. But spraying not only kills the aphids, it also kills the ladybugs—and any other beneficial insects hanging around. We can’t have our pesticides and our good bugs, too. Instead of aiming to eradicate every last bug from our gardens, it’s better to think in terms of balance. If keeping an aphid or two around makes the ladybugs happy, then that’s a small price to pay. Just make sure to wash your produce well before serving it for dinner!
Are ladybugs a good way to control aphids and other garden pests? When you consider the $14.95 price tag for 900 ladybugs (enough for 1,000 square feet, according to one company), you might decide they aren’t worth the cost. Instead of buying these insects, perhaps a better alternative is to make your yard ladybug friendly.
Ladybugs (and many other beneficial insects) supplement their insect diet with nectar and pollen, especially when storing up fuel for the winter. Make sure you have some of their favorite flowers available. Cilantro, wild mustards, wild carrot, parsley, and other flat-topped flowers are especially appealing. Organic Gardening recommends Bachelor’s Buttons, Sweet Alyssum, Borage, Agastache, Golden Marguerite (Anthemis tinctoria), and buckwheat, among others.
While they aren’t ideal, ladybugs are one more tool in our pest management toolkit. Next month, I’ll talk about some other biological controls gardeners have available.