Recent Advances in Biological Control of Submersed Aquatic Weeds

Abstract

The submersed aquatic plants hydrilla ( Hydrilla verticillata (L.f.) Royle), Eurasian watermilfoil ( Myriophyllum spicatum L.),and Brazilian egeria ( Egeria densa L.) are three of the worst invasive aquatic weed problems in the U.S., with mil- lions of dollars spent annually to control large infestations in all types of waterbodies. Historically, various control technol- ogies have been used to manage infestations of these sub- mersed species, including biological control. During the past five years, there has been renewed interest in biological con- trol of submersed aquatic weeds nationally, primarily in re- sponse to the discovery in Florida of several hydrilla biotypes that have developed resistance to the herbicide fluridone. This paper summarizes the current status of biological con- trol activities in North America during the past 10-15 years. It includes a preferred definition of biological control and de- scribes the different approaches currently used by practitio- ners in the field. It also covers the types of natural enemies commonly used as biological control agents and the various abiotic, biotic, and technical factors that have contributed to project successes and failures. Finally, priority areas are iden- tified where more resources are needed for research and outreach programs to increase the effectiveness and accep- tance of biological control technology for managing sub- mersed aquatic weeds in the future.