The Multicolored Asian Lady Beetle (Harmonia axyridis) is a highly effective predator intentionally introduced globally for biological pest control. The direct answer to whether Asian beetles eat aphids is yes; aphids make up the majority of their diet during the growing season. This beetle is one of the most widely recognized generalist predators used to manage pest populations in crops and gardens.
How Asian Beetles Hunt Aphids
Aphids are the primary food source for both the adult and larval stages of the Multicolored Asian Lady Beetle. The beetle’s two active life stages coincide with peak aphid infestations in agricultural settings and gardens. Adults actively search for aphid colonies, attracted by the visual appearance of infested plants and chemical cues.
The larval stage is the most aggressive aphid consumer and is responsible for the greatest pest reduction. A single larva can consume between 600 and 1,200 aphids throughout its four instars before it pupates. Adult beetles typically consume 15 to 65 aphids per day, though some can consume over 100. This sustained predation across both life stages helps control large infestations of pests like the soybean aphid.
Diet Beyond Soft-Bodied Pests
Although aphids are the preferred prey, the Multicolored Asian Lady Beetle has a broad, generalist diet that allows it to thrive even when aphid populations are low. The beetle readily preys upon a variety of other soft-bodied agricultural pests, including:
- Scale insects
- Mealybugs
- Spider mites
- Psyllids
They also consume the eggs and larvae of other insects, including those of moths and butterflies.
The beetle’s diet also extends to non-prey food sources. When insect prey is scarce, the beetles supplement their diet with plant materials such as pollen, nectar, and the sugary honeydew excreted by aphids. This dietary flexibility is a major factor in the species’ ability to survive and establish itself. However, this same flexibility can lead to problems, as the beetles are sometimes found feeding on ripening fruit, such as grapes and raspberries, especially when seeking sugars in the fall.
The Ecological Impact of the Multicolored Asian Lady Beetle
Despite its effectiveness as a pest controller, the Multicolored Asian Lady Beetle has a complex ecological impact in regions where it was introduced. Classified as an invasive species, its success is due to its superior reproductive capacity and predatory efficiency.
Competitive Displacement
The Asian beetle outcompetes native ladybug species for limited aphid resources. It is also an intraguild predator, meaning it preys on other beneficial insects that occupy the same niche. This includes consuming the eggs, larvae, and pupae of native ladybugs and other aphid-eating insects, contributing to the decline of local populations.
Household Nuisance
The Multicolored Asian Lady Beetle becomes a household nuisance pest during the fall, as large aggregations seek shelter to overwinter inside buildings. Once disturbed indoors, they secrete a foul-smelling, yellow-orange fluid that stains surfaces. They are also known to occasionally bite humans when searching for moisture.