Ladybugs, classified in the family Coccinellidae, are recognized insects in the garden, distinguished by their bright, dome-shaped bodies. The vast majority of the approximately 6,000 species worldwide are beneficial predators, not plant eaters. Most ladybug species are natural enemies of soft-bodied insects and play a significant role in ecological pest management. The few exceptions that consume plant matter are a small subset of this large beetle family.
The Primary Diet of Ladybugs: Pest Control
The primary function of most ladybugs in a garden ecosystem is their appetite for pest insects. They are valued by gardeners and farmers for their role as biological control agents against agricultural threats. Ladybugs, in both adult and larval stages, feed primarily on insects like aphids, which are their preferred meal.
They also consume a variety of other soft-bodied pests, including scale insects, mealybugs, whiteflies, thrips, and mites. When pests are scarce, ladybugs can survive on pollen and nectar, making them adaptable natural enemies. An adult female ladybug may consume up to 5,000 aphids during its lifetime to produce eggs.
Ladybug larvae, often described as tiny, spiky, alligator-like creatures, are more effective predators than the adults. These larvae are strictly carnivorous and can consume approximately 400 aphids before they enter the pupal stage. Adult ladybugs lay their eggs directly within pest colonies, ensuring their newly hatched young have an immediate and abundant food source.
Herbivorous Look-Alikes and Exceptional Species
Confusion arises because a few true ladybug species are herbivores, and several plant-eating insects resemble the beneficial beetles. The subfamily Epilachninae consists of these vegetarian ladybugs, which exclusively feed on plant tissue. The Mexican Bean Beetle (Epilachna varivestis) is a notable example; both its adults and larvae feed on bean plant leaves, causing significant damage.
Another destructive species is the Squash Beetle (Epilachna borealis), which targets plants in the squash and cucumber family. Unlike the smooth, glossy shell of most predatory ladybugs, these plant-feeding species often have a duller appearance. The difference is their diet, as these exceptional ladybugs can quickly defoliate crops rather than protecting them.
Gardeners may also confuse beneficial ladybugs with other plant-eating insects that have similar dome shapes and colors. The bright colors on most predatory ladybugs are a form of warning coloration, signaling to birds that they are distasteful. Distinguishing between a pest and a predator comes down to observing their behavior and the pattern of their markings.
Encouraging Ladybugs to Stay in Your Garden
Attracting and maintaining a healthy ladybug population involves providing habitat, non-prey food sources, and a chemical-free environment. Since ladybugs require water, offering a shallow dish with small stones or wet sand allows them to drink safely. Ground cover plants, mulch, and leaf litter provide shelter for adults to hide from predators and overwinter.
Pesticides, especially broad-spectrum varieties, should be avoided as they kill ladybugs along with the target pests, eliminating natural control. To supplement their diet when pest numbers are low, incorporate flowers that produce nectar and pollen, which serve as an alternative food source. Effective plants include those with clustered flowers that offer easily accessible pollen and nectar:
- Dill
- Fennel
- Yarrow
- Sweet alyssum
Gardeners can also plant decoy crops, such as nasturtiums, to attract aphids away from valuable plants, providing a concentrated food source. A consistent supply of both prey and plant resources is the most effective strategy for encouraging these beneficial beetles to establish a permanent presence.