Black aphids are eaten by a wide range of predators, including ladybugs, lacewing larvae, hoverfly larvae, parasitoid wasps, predatory midges, and even small birds like goldfinches and sparrows. In a healthy garden ecosystem, these natural enemies can reduce black aphid colonies by 70% to 100% without any intervention from you.
Ladybugs: The Most Familiar Aphid Predator
Ladybugs are the best-known aphid hunters, and they deserve the reputation. A single ladybug eats roughly 50 aphids per day and can consume around 5,000 over its lifetime. Both the adult beetles and their larvae feed on aphids, though the larvae (small, dark, alligator-shaped creatures you might not recognize) are equally aggressive hunters. The Asian lady beetle, a large orange species that may or may not have spots, is one of the most common aphid predators in North American gardens. Broad beans and other plants infested by black aphids actually release chemical signals that help ladybugs locate their prey from a distance.
Hoverfly Larvae
Adult hoverflies look like small, harmless bees hovering near flowers. Their larvae, however, are dedicated aphid predators. Each hoverfly larva can eat up to 400 aphids during its development. When hoverfly larvae are abundant in a garden or field, they can reduce aphid populations by 70% to 100%, according to Cornell University research. The larvae are translucent, slug-like creatures that you’ll find crawling directly through aphid colonies on stems and leaves. They feed on both adult and immature aphids.
Lacewing Larvae
Green lacewing adults are delicate, pale green insects with lace-patterned wings. Their larvae are the real predators. Sometimes called “aphid lions,” lacewing larvae have large, sickle-shaped mouthparts that they use to pierce and drain soft-bodied insects like black aphids, thrips, whiteflies, and spider mites. They’re so effective at controlling pest populations that they’re sold commercially for release in greenhouses and gardens.
Parasitoid Wasps
Parasitoid wasps don’t eat aphids in the traditional sense. Instead, they destroy them from the inside. A single female wasp lays one egg inside each of roughly 100 aphid nymphs. After hatching, the wasp larva feeds on the aphid’s internal tissues through three growth stages. About 7 to 10 days after the egg was laid, the larva kills the aphid and causes its body to become crusty and swollen, forming what’s called a “mummy.” The adult wasp then chews a small round hole and emerges.
If you see bloated, tan or brown aphid husks stuck to your plants, sometimes with tiny exit holes, parasitoid wasps are already at work. These wasps are tiny and harmless to humans. They’re one of the most effective natural controls for black aphid species like the black bean aphid.
Predatory Midges
The predatory midge Aphidoletes aphidimyza is a small fly whose larvae are specialized aphid killers. In controlled studies, predatory midges achieved 78% to 95% control of aphid populations. The adult females prefer to lay their eggs directly among aphid colonies on new plant growth. They do best in humid conditions, which is why they’re particularly effective in greenhouses or during damp weather. Like lacewings, predatory midges are available commercially for biological pest control.
Birds, Spiders, and Other Hunters
Insects aren’t the only animals feeding on black aphids. Small songbirds, particularly goldfinches and sparrows, eat aphids when foraging on plants. Spiders, harvestmen (daddy longlegs), earwigs, ground beetles, rove beetles, damsel bugs, and bigeyed bugs all contribute to aphid control as well. None of these individually have the impact of a ladybug or hoverfly population, but together they form a layered defense. A garden that supports diverse wildlife will naturally keep aphid numbers lower than a sterile one.
Why Ants Make the Problem Worse
If you’ve noticed ants marching up and down the same stems where black aphids cluster, that’s not a coincidence. Ants farm aphids for the sticky, sugary honeydew they produce. In exchange, ants actively protect aphid colonies from predators. They’ll attack ladybugs, lacewing larvae, and parasitoid wasps to keep their honeydew source alive. This means that even if your garden has plenty of beneficial insects, ants can prevent them from reaching the aphids. Controlling ant access to your plants, often by applying sticky barriers around stems or addressing ant nests nearby, is one of the most important steps in letting natural predators do their job.
How to Attract More Aphid Predators
The most effective way to bring aphid predators into your garden is to plant flowers that feed them during the stages of life when they aren’t hunting. Adult hoverflies, for example, need pollen and nectar. Sweet alyssum is one of the best options because it flowers continuously, providing a steady food source that draws hoverflies to your growing area. Research from the USDA found that alyssum interplanted with lettuce attracted enough hoverflies to significantly reduce aphid damage.
Dill, fennel, yarrow, and other small-flowered herbs and wildflowers serve a similar purpose for parasitoid wasps and lacewings. The key is having something in bloom throughout the growing season so predators stay in your garden rather than moving on. Avoiding broad-spectrum insecticides is equally important. Spraying for aphids kills the predators that would otherwise keep future outbreaks in check, often making the problem worse in subsequent weeks.