Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2007
Publication Date: 3/17/2010
Citation: Zhang, J., Wheeler, G.S., Purcell, M., Ding, J. 2010. Biology, distribution, and field host plants of Macroplea japana in China: an unsuitable candidate for biological control of Hydrilla verticillata. Florida Entomologist. 93(1) March 2010, pgs. 116-119. Interpretive Summary: Hydrilla verticillata is among the worst weeds in streams, rivers, and lakes in the southern US. This species forms dense stands, crowds out native vegetation, impedes navigation, and makes water management problematic. Hydrilla is controlled mainly with chemical herbicides; however both mechanical removal and biological agents (e.g. fish and insects) play some role. Since the discovery of herbicide resistance in hydrilla populations in Florida alternative forms of control, especially biological control, have become a high priority. Surveys for insects that feed on hydrilla in China discovered a beetle, Macroplea japana feeding underwater on the roots and stems. Subsequent studies determined that this insect completes one generation each year and occurs in the provinces Hubei, Hunan, and Guizhou. These beetles were found feeding as larvae on numerous aquatic plant species including Vallisneria spiralis, Potamogeton malaianus, Potamogeton maackianus, Potamogeton perfoliatus, Ottelia acuminata, Myriophyllum verticillatum, Nymphoides peltatum, and Alopecurus aequalis. Considering this wide range of plants, it is unlikely that M. japana will be used as a biological control agent for hydrilla.
Technical Abstract: The beetle Macroplea japana (Jacoby) (Coleoptera: Chrysomelidae) was regarded as a potential agent to biological control Hydrilla verticillata L.f. Royle. Herein we describe its discovery in South China and descriptions of the beetle biology, including its distribution and host plants. All stages of these beetles live underwater feeding upon the base of their host plant near the hydrosoil. A single generation is completed each year. Searches for the beetles were conducted in nine provinces but they were found only in Hubei, Hunan, and Guizhou. In the field, we found the beetle fed on nine host species including Hydrilla verticillata, Vallisneria spiralis, Potamogeton malaianus, Potamogeton maackianus, Potamogeton perfoliatus, Ottelia acuminata, Myriophyllum verticillatum, Nymphoides peltatum, and Alopecurus aequalis. Considering this wide host range, it is unlikely that M. japana will be used as a biological control agent for hydrilla.