Eastern U.S. Occurrences
Waterbodies infested with Hydrilla can be found in 70% of Florida's freshwater drainage basins, making it the most abundant aquatic plant in that state’s waters. Hydrilla is also widespread throughout Alabama; impoundments on the Tennessee River; eastern Mississippi; southeastern Tennessee; southwestern Georgia; South Carolina; eastern North Carolina; in Virginia’s Potomac, Rappahannock, and Appomattox Rivers and into the piedmont, in the tidal freshwater reaches of the Potomac River on the Virginia/Maryland border; along the western and northeastern shores of the Chesapeake Bay, including the Pautuxent River, where it is the most abundant plant species; Pennsylvania (in the Schuylkill River near downtown Philadelphia); eastern Kentucky; in ponds in Delaware; southeastern Connecticut; in a Cape Cod pond in Massachusetts; in southwestern Maine; in New Jersey’s Lower Delaware drainage; Indiana's Lake Manitou; Wisconsin; and since 2008, in three New York lakes in Suffolk and Orange Counties, and in Cayuga Lake in NY's Finger Lakes. Hydrilla can also be found at numerous sites west of the Mississippi River.
Cayuga Lake Inlet Infestation
H. verticillata was detected in the Cayuga Lake Inlet in Ithaca, New York in mid-August 2011 by staff of the Cayuga Lake Floating Classroom. A follow-up survey by Robert L. Johnson, a former researcher with the Cornell University Department of Ecology & Evolutionary Biology, now with Racine-Johnson Aquatic Ecologists, located extensive Hydrilla populations in several areas of the Inlet. As of early-September 2011, the Hydrilla appears to be localized to the Inlet, with no evidence of the plant in Cayuga Lake proper. This is the first detection of Hydrilla in upstate New York. The risk of the plant spreading to the rest of Cayuga Lake and other regional waterbodies in the Finger Lakes region is considered to be substantial. State, regional, and local officials and organizations, along with biologists from Cornell University are developing plans to control, manage, and prevent the spread of the invader, as well as outreach efforts to enlist the public's help in preventing the plant's spread.