Cornell University, Biological Control: A Guide to Natural Enemies in North America

Chilocorus kuwane larva. Chilocorus kuwanae adult.
Right: C. kuwanae egg laid against euonymus scale.C.Sadof
Center: C. kuwanae larva feeding on euonymus scale.C.Sadof
Right: C. stigma (left) and C. kuwanae (right).J.Davidson



Chilocorus kuwanae
(Coleoptera: Coccinellidae)

Chilocous kuwanae is a small black lady beetle imported from Korea as part of a biological control program for the euonymus scale, Unaspis euonymi. This scale is a serious pest that kills wintercreeper euonymus, a popular North American ground cover. C. kuwanae has been released by the USDA in most states east of the Mississippi River, five states in the central U.S., and in California. Field surveys show that C. kuwanae is widespread from Alabama to southern New England and westward to the Appalachian mountains.

Appearance

    C. kuwanae is a black lady beetle, about 3 mm long, with red spots. It looks quite similar to the native Chilocorus stigma, but it can be distinguished by the color, shape and location of the spot on its wings. Spots of C. kuwwanae tend to be deep red and rectangular and located near the center of the wing. In contrast, spots of C. stigma tend to be more orange-yellow, round and oriented more toward the head of the beetle.

Habitat

    Vegetation that is attacked by scales.

Pests attacked

    In North America., euonymus scales and other scales, such as the San Jose scale. In China, Korea and Japan, where it is common, C. kuwanae helps to keep several species of armored scales under control in citrus groves and on landscape shrubs.

Life cycle

    Beetles spend the winter as adults in leaf litter at the base of scale-infested plants. They become active and feed on scales when temperatures exceed 50°F in the spring. Adults lay bright orange eggs, singly or in small groups under the scale covers. Eggs hatch into brown larvae covered with black spines. Larvae will flip over or chew through scale covers to feed on the fleshy scale body. After 3 larval stages, larvae move to the underside of a leaf or to a crack or crevice on a twig or branch. There they become immobile and the larval skins split to form pupae. In the laboratory, it takes about a month to mature from egg to adult. In the midwest during the growing season, there are usually 3 generations.

Relative Effectiveness

    C. kuwanaeis noted for its voracious appetite. Each larval C. kuwanae must feed on over 100 scales to become an adult. In the United States, this appetite has caused the beetle to rapidly deplete the euonymus scale population at landscape release sites. Like many other lady beetles, C. kuwanae just flies away when food gets scarce. However, other scales such as San Jose scale and Oystershell scale can be used by adults as a food source.

Conservation

    In areas where this beetle is established, you can help it along by leaving leaf litter on the ground so that beetles have a safe place to spend the harsh midwestern winters. Despite reductions in numbers due to the exceptionally cold winter of 1993-94, some beetles survived where temperatures dipped to -27°F. In addition, you should adopt standard practices that conserve natural enemies. In the landscape, this means limiting pesticide use and using materials with short residual toxicities, such as horticultural oils or insecticidal soaps when pesiticides must be applied. Flowering plants may also contribute to the residence time of C. kuwanae adults. They have been reported to feed on nectar and pollen in the landscape.

    For general information about conservation of natural enemies, see Conservation in the Tutorial section on this site, or the Volume II, No. 1Feature Article on conservation in the Midwest Biological Control News Online.

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Weeden, C.R., A. M. Shelton, and M. P. Hoffman. Biological Control: A Guide to Natural Enemies in North America.
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Suggestions, corrections, and/or comments are appreciated: Contact Tony Shelton (ams5@nysaes.cornell.edu).
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