Ladybugs Are Good At Eating Aphids

When aphids threaten to overrun a garden, they are devouring plant tissue and stealing vital nutrients. They are the bane of many a gardener’s existence, but luckily, there is a natural enemy for them: ladybugs. A single adult female can eat up to a hundred aphids in a day. Ladybugs are voracious predators that feed on aphids, soft scale insects, thrips, spider mites, and leaf beetles. They also eat pollen and nectar. To encourage ladybugs in the garden, plant shallow flowers such as dill, coriander, and sweet alyssum that they can easily reach into.

Most ladybugs will hunt aphids all summer long. The harlequin lady beetle (Rodolia cardinalis), introduced to North America in the 1880s, is especially voracious and will also prey on other insects such as cottony cushion scale, soft scale, and cosmos.

In the field, one adult ladybug can eat up to 100 aphids per day, and each larva will consume about 400 aphids in three weeks before they pupate. To control aphids, plant a mix of early-, mid-, and late-blooming flowers to attract ladybugs all season long. These plants will provide aphid-eating nourishment as well as other pollen, nectar, and protein for the hungry ladybugs.

Scientists have found that ladybugs can eat aphids even in zero gravity. In fact, the first ladybugs sent into space were designed by school children in Chile. They hung from the edges of the onboard greenhouse and were observed crawling up stems to reach the aphids on their backs, just as they do on earth. When the aphids jumped down to escape, they dropped into the ladybugs’ mouths.

Like other insects, ladybugs have appetites for five major nutrient groups: carbohydrates, fat, protein, sodium, and calcium. But a study by Todd Ugine, a research associate in the lab of John Losey at Cornell University, found that aphid-eating ladybugs also have an additional appetite for sterols. A nutrient in the fat of aphids, sterols are essential to aphid-eating ladybugs, which are devoid of them naturally. In order to meet this dietary need, aphid-eating ladybugs will scour the leaves of their host plants for sterols.

If you are interested in introducing ladybugs to the garden, look for them at local nurseries or garden centers. They are often sold in the pupal stage and shipped to you in a tray of vermiculite. This is the best way to get them, as they will be healthy and ready to hunt aphids. Before releasing them, be sure to avoid chemical insecticides that leave toxic residues, and use mild insecticidal soaps or horticultural oils such as neem oil instead.