1 Controlling Hydrilla and Eurasian Watermilfoil with Fungal Pathogens from The People's Republic of China

watermilfoil or milfoil (Myriophyllum spicatum L.). Results of this research will be used to determine the direction of future efforts in using classical pathogen biological control research for management of these two nuisance aquatic weed species. BACKGROUND: The principle of classical biocontrol is to search for natural enemies of a target plant in regions of the world where the plant and its enemies coevolved. Because hydrilla and Eurasian watermilfoil are widely distributed throughout the Old World, and their exact center of origin remains uncertain (Cook and Luond 1982; Couch and Nelson 1985), the search strategy to find natural enemies has been to survey specific areas in the reported range of the two species. Through support from the U.S. Army Engineer Aquatic Plant Control Research Program (APCRP), a classical pathogen biological control effort was launched in 1994. Survey work was initiated in Europe for pathogens of Eurasian watermilfoil (Harvey and Evans 1997) and in The People’s Republic of China (PRC) ( Shearer 1997a) for pathogens of both milfoil and hydrilla. Broadening the scope of the biological control program through foreign exploration for pathogens has the advantage of not only strengthening the existing pathogen program that currently uses only endemic organisms but enhancing the insect biocontrol program by increasing the number and variety o