Iowa Insect Information Notes

Ladybug - Multicolored Asian Lady Beetle

Ladybug - Multicolored Asian Lady Beetle

Asian Lady Beetles

The multicolored Asian lady beetle (Harmonia axyridis), has become common throughout the United States and all of Iowa. It is well known for the annoying habit of accumulating on the sides of buildings and wandering indoors during the fall. Asian lady beetles are a beneficial biological control in trees during the summer, and in fields and gardens during the fall, but can be a severe household nuisance during late fall and winter. Wooded residential and industrial areas are especially prone to problems.

The origins of the Asian lady beetles are not clear, although it appears the current pest species was not purposefully released in the United States or in Iowa. Beetles that arrived by accident in ports such as New Orleans in the late 1980s have crawled and flown all by themselves to all corners of the country.

Description

The multicolored Asian lady beetle is 1/3 inch in length; dome-shaped; yellowish-orange to red with variable black spots on the back. Deep orange is the most common color. The 19 black spots may be faint or missing. There is a black “W” shaped mark on the thorax.

Asian lady beetles, like other accidental invaders, are "outdoor" insects that create a nuisance by wandering indoors during a limited portion of their life cycle. They do not feed or reproduce indoors; they cannot attack the house structure, furniture, or fabrics. They cannot sting or carry diseases. Lady beetles do not feed on people though they infrequently pinch exposed skin. Lady beetles may leave a slimy smear and they have a distinct odor when squashed.

Asian lady beetles follow their instinctive behavior and fly to sunny, exposed surfaces when preparing to hibernate through the winter. The time of beetle flight varies but is usually from mid-September through October (depending on weather). Light colored buildings and walls in full sun appear to attract the most beetles.

Management

Sealing exterior gaps and cracks around windows, doors, eaves, roofs, siding and other points of access before the beetles appear can prevent unwanted entry. Experience suggests, however, that comprehensive pest proofing is time-consuming, often impractical and usually not 100% effective.  For large infestations with intolerable numbers of beetles, spraying pyrethroid insecticides such as permethrin or esfenvalerate to the outside of buildings when the beetles appear may help prevent pest entry. Homeowner insecticides other than pyrethroids usually do not provide satisfactory prevention.

Long-term relief may come from planting trees that will grow up to shade the south and west sides of the house. The most practical control for beetles already inside is to vacuum or sweep them up and discard. Indoor sprays are of very limited benefit. Interior light traps are available.

We also have pictures of other lady beetles

See also our information on Asian lady beetle traps.

Below: an Asian lady beetle munches down on soybean aphids. Soybean aphids are a pest of soybean.

Asian lady beetle feeding on soybean aphids

Updated 07/29/2005 - 2:52pm