Ladybugs (family Coccinellidae) are recognized insects in gardens. Their presence near herbs like basil frequently prompts questions about whether they are harming the plants. Understanding what they eat is essential for appreciating their role in a healthy garden ecosystem.
Ladybugs Are Predators, Not Plant Eaters
Ladybugs do not consume basil, lettuce, or other common garden plants because they are biologically equipped to be predators. They are classified as beetles, and their mouthparts are adapted for chewing and grasping small prey. This morphology is specialized for hunting and crushing soft-bodied insects, not for tearing or grinding plant tissue.
The common species found in North American gardens, such as the Convergent Lady Beetle or the Seven-spotted Lady Beetle, are overwhelmingly carnivorous. When a ladybug is observed on a basil leaf, it is nearly always there in search of pests, not to eat the herb itself. Finding a ladybug near a plant often signals a problem with tiny pests.
A small fraction of the Coccinellidae family, specifically the subfamily Epilachninae, includes herbivorous species like the Mexican bean beetle or the squash beetle. These plant-eating exceptions are uncommon and can be easily distinguished from the beneficial, predatory species. The vast majority of ladybugs are considered beneficial allies to gardeners.
The Primary Diet of Ladybugs
The primary food source for most ladybug species consists of soft-bodied garden pests that feed on plant sap. Their diet revolves heavily around aphids, which cluster on stems and the undersides of leaves. Ladybugs are such effective aphid predators that their presence can quickly suppress a localized infestation.
A single adult ladybug can consume between 50 to 75 aphids per day. A female will lay her eggs near a colony of these pests to ensure an immediate food source for her offspring. The larval stage, which looks like a tiny, gray or black alligator with orange markings, is often more voracious than the adult beetle. These larvae can consume hundreds of aphids during the few weeks it takes them to mature.
Beyond aphids, ladybugs also feed on other common garden nuisances, including scale insects, mealybugs, spider mites, and whiteflies. They will also eat insect eggs. When pest populations are low, adult ladybugs supplement their diet with pollen, nectar, or honeydew, but their preference remains the protein-rich pests.
Encouraging Ladybugs for Natural Pest Management
Utilizing ladybugs for pest control focuses on retention and attraction, rather than relying on the introduction of mass-purchased insects. The best way to keep ladybugs in the garden is to avoid using broad-spectrum chemical pesticides, which kill beneficial insects along with the target pests. Even organic sprays can harm ladybugs, so use them selectively or avoid them completely.
A steady supply of water and shelter also encourages ladybugs to stay and reproduce. Placing a shallow dish of water with small stones provides a safe drinking source, preventing the beetles from drowning. Offering groundcover or leaving some dried plant stems provides suitable locations for the adults to shelter or overwinter.
Gardeners can actively attract ladybugs by planting companion flowers that offer supplementary pollen and nectar. Herbs like dill, fennel, and yarrow are particularly effective because their tiny, flat-topped flower clusters make pollen easily accessible to the beetles.
Sweet alyssum and cosmos are other flowering plants that provide sustenance when prey is scarce. Maintaining a small population of pests, perhaps on a designated “trap crop” like nasturtiums, helps ensure that ladybugs have a consistent food supply, keeping them from flying away to find better hunting grounds.