Chinese Coccinellidae for biological control of the hemlock woolly adelgid: description of native habitat

Abstract

The hemlock woolly adelgid, Adelges tsugae Annand, is generally believed to be native to Asia and is known to occur in India, Japan, and China. In China, there are approximately four species of hemlock that grow in 14 provinces. We explored regions of the Southwestern Plateau in Yunnan, Sichuan, and Shaanxi Provinces for the adelgid and its natural enemies. The montane- forests of this region are largely in their natural state and noted for their biological diversity. We found the hemlock woolly adelgid in all three provinces and on each hemlock species examined (Tsuga dumosa (D. Don) Eichler, T. forrestii Downii, and T. chinensis (Franch.) Pritz.). More than 9 families of natural enemies were found in association with A. tsugae in China. One family, the Coccinellidae, is exceptionally diverse and seems to have an important role in maintaining the adelgid at low population densities. Of the 50+ species of lady beetles found on hemlock, at least 25 are new to science. Nine species are known to feed on HWA and three have been imported for further evaluation as biological control agents. The biodiversity of the lady beetles is discussed in relation to the habitat and climate of their native range compared with potential release sites in the United States.