DISTRIBUTION OF HYDRILLA IN NORTHERN CHINA - IMPLICATIONS ON FUTURE SPREAD IN NORTH-AMERICA

Hydrilla (Hydrilla verticillata L.f. Royle) has greatly expanded its r ange in the USA since it ''escaped'' cultivation in Florida streams in the early 1950s. It now occurs in all the southern border states, as well as along the eastern seaboard as far north as Delaware, but furth er northward expansion by hydrilla in the U.S. appears controversial. We have recently been collecting potential biological control agents f or hydrilla in China, and present our observations on the density and distribution of hydrilla in northern China. These are supplemented by data from hydrilla specimens in the herbaria of various Chinese scient ific institutions, as well as literature records from northern Asia. T hese collections, along with comparisons of climatic data, indicate th at hydrilla has the potential to grow in aquatic habitats almost anywh ere in North America, including Canada and parts of Alaska.