Most ladybugs do not eat plants. The vast majority of the roughly 5,000 ladybug species worldwide are predators that feed on aphids, scale insects, and mites. However, a small group of ladybugs in the subfamily Epilachninae are genuinely plant-eating, and they can cause real damage to garden crops. Many predatory species also snack on pollen and nectar as a supplement, but this light grazing doesn’t harm plants.
Why Most Ladybugs Are Plant-Friendly
The ladybugs you’re most likely to see in your garden are hunters. They eat soft-bodied insects, especially aphids, and a single ladybug can consume dozens of them per day. This is why gardeners consider them beneficial and sometimes buy them for pest control. Some predatory ladybugs sip nectar or nibble pollen when prey is scarce, and in doing so they actually help with pollination by transferring pollen between flowers. One genus, Psyllobora, feeds on fungus rather than insects or plants, making it useful against problems like powdery mildew on grapevines.
The Plant-Eating Exceptions
Two ladybug species in North America are true plant feeders: the Mexican bean beetle and the squash beetle. Both belong to the subfamily Epilachninae, and both feed on plants as adults and larvae. The Mexican bean beetle targets beans and other legumes, while the squash beetle feeds on cucumbers, squash, pumpkins, and other members of the cucurbit family.
The Mexican bean beetle is native to southern Mexico and was first detected in the western United States in 1849. It has since spread across much of the country, with populations in the Rocky Mountain states and a separate eastern population extending into northern Florida. The squash beetle has a wide distribution across the eastern U.S. These are the only two members of Epilachninae commonly found in American gardens, and they’re the rare ladybugs that gardeners should worry about.
How to Tell Them Apart From Helpful Ladybugs
Mexican bean beetles are about the same size as common ladybugs (roughly a quarter inch long) and have a similar rounded shape, which makes misidentification easy. The key difference is their spot pattern: Mexican bean beetles have eight black spots on each wing cover and none on the section behind their head. Their color tends toward copper or orangish-yellow rather than the bright red of many beneficial species.
Squash beetles are easier to distinguish because they’re noticeably larger, about twice the size of a typical ladybug. Both species lay yellow eggs in clusters on the undersides of leaves, and their larvae are yellow and covered in branching spines, looking nothing like the smooth, dark larvae of predatory ladybugs.
What Plant Damage Looks Like
If plant-eating ladybugs are in your garden, the damage has a distinctive pattern. Both adults and larvae feed from the underside of leaves, chewing away green tissue in small patches between the leaf veins. This creates a lacy, see-through appearance that’s often described as “skeletonized.” Over time, the damaged leaves lose moisture, turn brown, and dry out. On beans, you’ll notice this lace-like damage on the lower leaf surfaces first. Heavy infestations can defoliate entire plants and significantly reduce your harvest.
Managing Plant-Eating Ladybugs in Your Garden
The challenge with plant-eating ladybugs is controlling them without harming their beneficial relatives. Broad-spectrum insecticides will kill both types, so targeted strategies work better.
- Row covers: Draping lightweight fabric over your bean or squash rows right after planting creates a physical barrier. You can leave the covers on through harvest.
- Hand removal: Crushing egg clusters, larvae, and adults by hand is effective in small gardens. Check the undersides of leaves regularly, since that’s where all life stages congregate.
- Trap planting: In gardens with heavy Mexican bean beetle pressure, planting a small patch of beans early in the spring draws overwintering adults to those plants first. Once the trap crop is fully infested, pull the plants and seal them in plastic bags to destroy the beetles before planting your main crop.
- Beneficial wasps: A tiny parasitic wasp called Pediobius foveolatus specifically targets Mexican bean beetle larvae. Releasing these wasps when you first spot larvae gives them the best chance of establishing control.
None of these methods will harm the predatory ladybugs that are keeping aphids off your tomatoes and roses. That distinction matters, because losing your beneficial ladybug population to a broad pesticide application often creates worse pest problems down the line than the bean beetles themselves.