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Asian Lady Beetle

Background

The multicolored Asian lady beetle (Harmonia axyridis) is native to Asia, but has become common throughout much of the United States. Federal, state and private entomologists have released the insect at a number of locations throughout the United States in an attempt to naturally control insect pests in trees. There are also several reports of accidental entries from international cargo ships arriving at various port cities, notably New Orleans.

Description

The multicolored Asian lady beetle occurs in many color combinations. Adult beetles are oval and convex, measuring roughly 6 mm long and 5 mm wide. North American populations have a mix of individuals ranging in color from pale yellow-orange to bright red-orange, with or without black spots on the wing covers. The pronotum (top covering of middle body part) is white to straw-yellow with several black spots joined to form two curved lines, an M-shaped mark or a solid trapezoid.

Life cycle

The multicolored Asian lady beetle has four distinct life stages: egg, larva, pupa and adult. It also has multiple generations per year. Beetles spend the winter as adults in protected sites. Eggs are laid in the early spring on the undersides of leaves and generally hatch in three to five days. The larval stage lasts 12 to 14 days, and the pupal stage, which takes place on leaves, lasts five to six days. After emergence, some adults can live as long as two to three years under optimal conditions.

Damage

Outdoors during the growing season, multicolored Asian lady beetles are beneficial aphid predators and also control other soft-bodied insects associated with trees, shrubs, ornamental plants and agricultural crops.

The beetles are attracted to houses with light-colored exteriors, such as white or yellow, and will often congregate in areas exposed to afternoon sun. Although they will not cause structural damage to houses like termites, they emit an unpleasant odor and can stain walls and fabrics if agitated or crushed. Lady beetles can cause allergies and skin irritations in some people, but are not poisonous or otherwise harmful to humans, pets or property. The beetles do not carry disease, but can bite in rare cases.

Control

Non-chemical control

Multicolored Asian lady beetles enter the house through small openings around doors, windows and utility access points. In addition, they can enter through siding gaps, cracks and attic vents. Sealing those entry points is the best method of keeping Asian Lady beetles and other pests from entering the home.

Use a high-quality silicone caulk to seal all cracks. To remove beetles in the home, use either a broom and dust pan or a vacuum cleaner. When using the vacuum, be sure to change the bag or empty the canister to the collected beetles from escaping.

Chemical control

Exclusion

Fast-acting, residual formulations of synthetic pyrethroids (e.g., cypermethrin, cyfluthrin, lambda cyhalothrin and deltamethrin) can be applied around eaves, attic vents, windows, doors, siding and other likely entry points for pests.

The key is to start treatments in late September or early October before the beetles enter buildings to overwinter. Once the beetles are indoors (i.e., winter or early-spring), such treatments are ineffective. These sprays serve as a chemical barrier, preventing the insects from entering, so timing and thorough coverage are essential for effective control.

Large-scale control

If the beetles have entered, do not use insecticides except for severe cases of large and persistent lady beetle infestations. Indoor pesticide applications have limited effectiveness since large numbers of these insects typically hide in inaccessible areas.

If necessary, residual pyrethroids appear to be the most effective, but they must be applied directly to the beetles or to the surfaces they crawl over. Different companies may market products under a variety of trade names that contain a residual pyrethroid as the active ingredient. If you need to spray, make sure that you use an aerosol insecticide labeled for household insects and do not forget to remove the dead beetles.

Do not use any type of aerosol fogger or “bug bomb” in an attempt to control lady beetles. Such chemical treatments are not warranted. These treatments do not control the majority of lady beetles behind walls and other unseen areas. In addition, the active ingredient in these “bug bombs” has limited effectiveness against the pests. Overuse of these products can lead to unnecessary human exposure. These products can actually increase some indoor pest problems when scavenging pests such as ants, carpet beetles, and larder beetles move in to feed on accumulated dead insects.


Reviewed by: Daniel Frank, Extension Service Entomology Specialist
Last Reviewed: September 01, 2013