Ladybugs, belonging to the Coccinellidae family, are familiar insects in home gardens, recognized by their dome-shaped bodies and bright colors. Gardeners often observe these beetles crawling on fruiting plants, such as tomatoes. This observation sometimes leads to the concern that ladybugs might be feeding on the crop. To understand the ladybug’s true role in the garden, it is important to examine why they visit plants like tomatoes and what their actual diet consists of.
Why Ladybugs Do Not Eat Tomatoes
The vast majority of ladybug species are carnivorous predators. They are not equipped to eat the tough, fibrous material of a tomato plant. Their mouthparts are specialized for crushing the soft bodies of small insects, not for tearing through the thick skin of a tomato or the structure of a leaf. If you find a ladybug on a tomato plant, it is using the plant as a habitat or a hunting ground, not as a food source. The beetle is there because the tomato foliage is often infested with the exact pests that make up its primary diet.
The Ladybug Diet: Beneficial Garden Predators
Ladybugs are highly valued by gardeners and farmers because they are voracious consumers of soft-bodied garden pests. Their main prey is the aphid, a sap-sucking insect that can quickly devastate plant health. An adult ladybug can consume up to 50 aphids per day, and potentially up to 5,000 over its lifetime. Beyond aphids, ladybugs also prey on scale insects, mealybugs, and mites. The juvenile, or larval, stage of the ladybug is an even more aggressive hunter than the adult, consuming hundreds of aphids before they pupate.
Identifying Ladybug Species and Look-Alikes
Confusion regarding ladybug feeding habits often stems from misidentification, as not all spotted beetles are beneficial. The Asian Lady Beetle (Harmonia axyridis), an invasive species, is the most common look-alike. It can be distinguished by a distinct black “M” or “W” marking on the white plate behind its head, called the pronotum. While native ladybugs are generally a vibrant red with seven distinct, symmetrical black spots, the Asian Lady Beetle can range in color from pale yellow to dark orange and may have anywhere from zero to nineteen irregular spots. True ladybug larvae are beneficial predators with an alligator-like appearance, which sets them apart from the larvae of plant-eating beetles, such as the Mexican Bean Beetle.
How to Encourage Ladybugs to Stay
Creating an environment that encourages ladybugs to remain in the garden ensures a continuous source of natural pest control. The most effective method is eliminating the use of broad-spectrum pesticides, which kill ladybugs and their prey indiscriminately. Allowing a small, manageable population of pests, such as aphids, to persist acts as a necessary food source to attract and sustain the beneficial beetles. Ladybugs also need supplementary food and shelter when their primary prey is not abundant.
Providing Food and Shelter
Planting companion flowers with flat-topped blooms provides easy access to pollen and nectar. These flowers include:
- Dill
- Fennel
- Yarrow
- Cosmos
Providing shallow water sources, like a dish with small pebbles for safe landing, is also helpful. Leaving ground cover, mulch, or dead stems until spring offers necessary shelter and overwintering sites.