Monday, November 5, 2007

Insects - Multicolored Asian Lady Beetle

Multicolored Asian Lady Beetle
Photo by Bill Ree, Texas A&M University,

One of the fall nuisance pests is the multicolored Asian lady beetle. It congregates on the walls of houses and can enter to overwinter in houses. However, this is also a beneficial insect and populations have increases recently as it is one of the natural controls for soybean aphid in soybean fields. The following is an article on this insect.

The multicolored Asian lady beetle is one of several species of lady beetles in Delaware . Adult multicolored Asian lady beetles exhibit the familiar oval lady beetle shape. Slightly larger than most of our native species – about 1/4" long by 3/16" wide – they are variable in color. Adults may be yellow, orange or red with black spots of various sizes on the wing covers. Beetles with 2, 4, 6, 10 and up to 19 spots have been found; some have no spots. The pronotum often has a "M"-like shape of black on the white- or cream-colored exoskeleton. When viewed from above, the head is concealed by the pronotum.

The life cycle from egg to adult takes about 36 days, beginning in mid-spring while the weather is still cool. The eggs are laid on the undersides of leaves of low-growing ornamentals, roses, wheat, tobacco, and other crops. Eggs clustered with 10 to 20 in one spot are yellow-orange and stand upright on lower leaf surfaces. They take from 3 to 5 days to hatch. The larvae are elongate and flattened with the familiar "alligator" shape of immature lady beetles.
The multicolored Asian lady beetle prefers to feed on host insects that live within trees. Favorite feeding hosts include maple, walnut, willow, and oak. Both larvae and adults feed on various aphids, certain scales, and a few other insects. It is an effective predator of aphids on pecan and apple trees, in evergreens, on ornamental shrubs, roses, and other plants. Beetle populations tend to explode when there is an abundance of aphids, often to the detriment of local aphid populations.

Although the multicolored Asian lady beetle is an important biological control agent, it can become a nuisance when adults aggregate in large numbers on homes or other buildings during autumn. It is sometimes called the "Halloween" beetle because it shows up in homes in late October. The massed beetles typically cluster on sunny, southwest sides of light-colored houses, barns, farm silos, rock outcroppings or structures where nearby crevices serve as overwintering sites.

Homeowners complain when hundreds/thousands of beetles are observed clustering on the side of their house. As daytime temperatures cool the beetles seek to enter by crawling through openings such as uncaulked window frames. Once inside, they cluster together. They do not bite, sting, or carry human diseases, they do not feed on wood, clothing, or food, nor do they breed indoors, but there sheer numbers can be a nuisance. They also create problems when they become active in February and March during warm, sunny days and attempt to return outside. During this time, they show up at windows as they attempt to leave the house.

Prevention is the key to managing nuisance populations of the multicolored Asian lady beetles. The easiest way to dispose of live/dead beetles inside the home during the fall or winter is with a vacuum cleaner or broom. Most beetles emerge from over winter hibernation during a 3- to 6-week period and will not survive more than a few days indoors. As they attempt to escape to their natural habitat outdoors, some inadvertently disperse into living areas. Since the beetles are attracted to light, they are often seen around windows and lighting fixtures. As the weather continues to warm, the beetles disperse outdoors and they cease to be a nuisance.
From the factsheet "Multicolored Asian Lady Beetle" by Dewey M. Caron, Extension Entomologist, University of Delaware

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