Meet One of Our Dedicated Partners

Posted on Jan 23, 2016

ladybugonlupinestocSue Hubbel, author of Broadsides from the Other Orders: A Book of Bugs, dubbed lady beetles “the panda of the insect world.” It’s easy to believe that the phrase “cute as a bug” refers to the cheery, polka-dotted beetle. But, while even small children can recognize a typical lady beetle, ladybug to their market friendlier name, few of us really know much about this gardener’s good partner.

The commonly sold convergent lady beetle is a West Coast native. The introduction of a native insect for pest management is known as augmentative pest control, and can be a successful technique. In the case of the convergent lady beetle, however, garden releases are generally unreliable for pest control, primarily because of the beetle’s natural life cycle. Lady beetles form aggregations in the lower elevations of the Sierra Nevada, where they are commercially collected for sale. Beetles collected from over-wintering aggregations disperse quickly when released into the garden, rarely stopping to feed. Beetles collected from late spring aggregations may not disperse quickly when released but eat relatively few prey. They survive the summer on high fat reserves acquired from eating pollen and nectar in the mountains. Overzealous collection of lady beetle aggregations may be producing a “shadow effect” in parts of the Central Valley, where fewer beetles are returning to their natural habitat. Since purchasing lady beetles is of questionable value, and most useful species of lady beetles are unavailable commercially, how can gardeners encourage this useful predator?

To begin with, not all species of lady beetles migrate, and even convergent lady beetles have some year-round populations in milder areas. Lady beetles may form clusters, or aggregations, of anywhere from hundreds to thousands of individuals, and spend the winter sheltered under leaf litter and around the bases of perennial bunch grasses and ground covers. Providing winter habitat in the landscape, and including season-long nectar and pollen sources as alternative food, encourages lady beetles to stay in the garden even when there are no aphids or other pests around.

Good pollen and nectar choices are plants in the umbel family (Apiaceae), such as dill, and the daisy family (Asteraceae). They also like perennial fall asters, sunflowers, and cosmos—all suitable insectary plants over a wide geographic area. By providing conditions that attract and maintain native populations of insects, and minimizing or even eliminating the use of pesticides, we are practicing conservation biological control, by far the easiest and least expensive way for gardeners to encourage many species of helpful insects.

Once enticed to take up residence in the garden, the appetite of the lady beetle is nothing short of amazing, and certainly not lady-like! Many coccinellids are specialist predators, eating only certain other species of insects. Depending on species, a single larva may eat 350 aphids before it pupates; an adult may eat 5,000 aphids in a lifetime. It is fascinating to watch the voracious lady beetles cleaning up a colony of aphids. Scale-eating species can be equally effective, but, since the beetle larvae live under the scales, they are more difficult to detect. Other lady beetles specialize on mealybugs, whitefly, mites, and insect eggs. Some lady beetles eat a more general diet, snacking on a variety of pests.