Publication Abstract

Monoecious Hydrilla - The Aquatic Weed for the New Century?

Madsen, J. D. (2013). Monoecious Hydrilla - The Aquatic Weed for the New Century? Aquatic Plant Management Society 53rd Annual Meeting. San Antonio, TX.


Research has identified at least twenty-six biotypes of hydrilla, ranging from tropical to cool temperate in origin. At present, only two of these biotypes are known for the United States: a warm subtropical biotype that is dioecious and produces pistillate flowers, and a temperate monoecious biotype. While the 1980ís to 1990ís were dominated by news of the frontal advance of dioecious hydrilla as the major submersed problem plant, the new century has seen the introduction of widely-dispersed populations of monoecious hydrilla. Monoecious hydrilla is very successful in establishing and dominating cool temperate lakes of the Great Lakes region, and is currently displacing dioecious hydrilla in mid-continental reservoirs from Virginia to Tennesee and even north Alabama. Phenologically, monoecious hydrilla is much more like native temperate plants than dioecious hydrilla; with propagules that both sprout and go dormant at approximately the same time as native species. Unlike dioecious hydrilla, it will go completely dormant to subterranean propagules. In many ways, it is better adapted to temperate North American lakes than dioecious hydrilla. Despite common wisdom, it is also extremely competitive with native species, and forms a dense surface canopy like the dioecious biotype. In appearance, it is very easily mistaken for the native elodea (Elodea canadensis). While some research has been done on monoecious hydrilla, much more is needed for natural resource managers to be as well informed on monoecious hydrilla as they are on dioecious hydrilla.