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Multicolored Asian Lady Beetles

Lady beetles are beneficial because they feed on insects that can damage plants in gardens, landscapes, and agricultural crops. However, one lady beetle species, the multicolored Asian lady beetle, Harmonia axyridis, has become very troublesome for homeowners in Minnesota and other places throughout the United States.

Identification

Multicolored Asian lady beetles are about 1/3-inch long and vary in their appearance. They range in color from orange to yellow to red or even black. The average beetle will typically have 19 black spots on its wing covers. However, some of the beetles have no spots at all. A distinguishable feature can be found behind the head in most specimens that looks like the letter “M”.

Habits

Multicolored Asian lady beetles are native to Asian. They feed primarily on aphids and other small, soft-bodied insects found in trees and plants. During the fall, these insects are found living in large quantities on the white colored cliffs in Asia to seek shelter for the winter. In Minnesota, these lady beetles are attracted to contrasting colors found on the west and south sides of tall or prominent buildings in mid September to late October. These insects can enter a home through very small cracks around door, windows, under siding, or along the roofline. They gather together in clusters during the winter months and remain in a dormant stage. They will sometimes migrate towards the warmer temperature found on the inside of the house. However, there life is short-lived inside due to the lack of an adequate food source.

Damage

Although, multicolored Asian lady beetles can be a nuisance when they occur in large numbers, they do not damage homes or other property. These lady beetles cannot sting and they do not carry disease. They can pinch the skin and cause minor, short-lived discomfort. They can secrete a strong smelling yellowish liquid from the joints of their legs, a process called reflex bleeding. They use this to discourage predators or at other times when they are stressed. This liquid can also stain light colored surfaces. Repeated exposure to dead lady beetles can cause an allergic reaction in some individuals.

Control

Prevention is the most effective step in managing lady beetles. Check the outside of your home for spaces and cracks that may allow an easy entry for insects. Make any necessary repairs by the end of August to mid September. Physical exclusion alone will not always stop them from getting inside. In those cases, a residual insecticide will need to be applied to the exterior to maintain control. The treatment must be applied before they enter in order to be effective. The timing will depend on the weather, but typically, it should be applied in September. Any beetles found inside should be removed by vacuuming them up. Once they have moved into wall voids there is no practical control to prevent them from emerging later during winter or spring. At that point the only means of control is to remove them as they are seen.

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