Asian lady beetles are voracious predators that feed primarily on aphids and other soft-bodied insects. A single adult can eat 15 to 65 aphids per day, and during its larval stage, one beetle consumes anywhere from 90 to 370 aphids before reaching adulthood. But their diet extends well beyond aphids, and some of their eating habits cause real problems for both native ecosystems and agriculture.
Aphids and Other Soft-Bodied Insects
The core of the Asian lady beetle’s diet is soft-bodied insects: aphids, scale insects, and psyllids. They’re not picky about which species of aphid they target. Cornell University lists pecan aphids, balsam twig aphids, and pine bark adelgids among their documented prey. This broad appetite is exactly why the USDA originally introduced them to North America as biological pest control agents.
The numbers are impressive. Larvae average about 23 aphids per day across their developmental stages, while adults eat 15 to 65 per day depending on the aphid species available. Some estimates put adult consumption even higher, at 90 to 270 aphids daily under ideal conditions. This feeding capacity makes them genuinely useful in agricultural settings. In soybean fields, for instance, even a modest population of Asian lady beetle larvae (one per seven plants) can suppress explosive aphid growth if the beetles arrive early enough in the season.
Pollen, Nectar, and Damaged Fruit
When insect prey runs low, Asian lady beetles shift to plant-based food sources. They’ll feed on pollen and nectar as a stopgap. In autumn, they tend to aggregate on late-season fruits like grapes, apples, and raspberries, though they generally feed only on fruit that’s already been damaged by birds or other insects rather than puncturing intact skin themselves.
This fruit-feeding behavior matters most for grape growers. As fall approaches and insect prey populations decline, the beetles move into vineyards and shelter inside grape clusters, likely seeking sugars and carbohydrates before winter hibernation. They don’t cause direct yield loss since they don’t attack undamaged berries, but their presence creates a different kind of problem entirely.
The Wine Taint Problem
When Asian lady beetles get crushed along with grapes during harvest, they release a compound from their body fluid that produces peanut, bell pepper, and earthy flavors in the finished wine. This “lady beetle taint” is detectable at astonishingly low concentrations. Most sources agree that just one beetle per pound of grapes creates a taint noticeable to casual wine drinkers. Trained tasters can detect it at even lower levels, around one to two beetles per 30-pound harvest container.
The beetles release this compound either when they’re crushed at the winery or through a defensive mechanism called reflex bleeding, where they excrete fluid from their leg joints when stressed. Neutral wines like Chardonnay are more vulnerable than aromatic varieties like Riesling, because there’s less natural flavor to mask the off-notes. Trained panelists have detected the taint at concentrations as low as 0.3 parts per trillion in Chardonnay.
Eggs and Larvae of Native Ladybugs
One of the more troubling parts of the Asian lady beetle’s diet is other ladybugs. They’re aggressive intraguild predators, meaning they eat the eggs and larvae of native ladybug species. This isn’t unusual behavior in the insect world (native ladybugs also eat Asian lady beetle eggs when they find them), but Asian lady beetles are simply better at it. Combined with their ability to outcompete natives for aphid prey, this predatory edge has contributed to population declines in several native ladybug species across North America.
Cannibalism within their own species also occurs. Asian lady beetle larvae will eat unhatched eggs from the same cluster if food is scarce, giving early-hatching individuals a protein boost at the expense of their siblings.
How Diet Changes With Life Stage
The beetle’s nutritional needs shift as it grows. Larvae are dedicated predators that spend virtually all their time hunting soft-bodied insects. They need protein-rich meals to fuel rapid growth through four larval stages before pupating. Adults maintain a high-protein diet when prey is available but are more flexible, supplementing with pollen, nectar, and fruit sugars. This dietary flexibility is part of what makes them so successful as an invasive species: when one food source dries up, they pivot to another.
Heading into winter, adults stop feeding and enter a dormant state, often inside homes and buildings. They survive on stored fat reserves accumulated during their fall feeding period. Once spring arrives, they resume hunting aphids and other prey as insect populations rebound.