Parks, Recreation and Historic Preservation

Press Release

September 09, 2022

Dan Keefe (518) 486-1868 |

First Occurrence of Hydrilla Found at Harriman State Park in Lake Sebago


Boaters should follow "Clean, Drain, Dry" practices to prevent spread of invasive species  

The New York State Office of Parks, Recreation and Historic Preservation (State Parks) and Department of Environmental Conservation (DEC) have identified hydrilla (Hydrilla verticillate), an aquatic invasive species, at Lake Sebago in Harriman State Park, which was first reported to the two agencies during routine surveys by the Lower Hudson Partnership for Regional Invasive Species Management.

Hydrilla is an aquatic plant found in Asia that has since spread to the United States and has become one of the most difficult aquatic invasives to control and eradicate. It first appeared in New York State in 2008, and is currently identified in 12 counties across the state. 

State Parks' Division of Environmental Stewardship and Planning is working with the DEC's Bureau of Invasive Species and Ecosystem Health, and Lower Hudson Partnership for Regional Invasive Species Management to assess and map the extent of the infestation at Lake Sebago to determine proper management actions.

"Hydrilla is notorious for spreading quickly, forming dense mats that greatly hinder boating, swimming, and fishing while displacing our native species. It is prudent of us to understand where this invasive species is within Lake Sebago and take measures to try and control the population before it spreads further," said State Parks Deputy Commissioner for Environmental Stewardship Ron Rausch.

Boaters should always follow the Clean, Drain, Dry best practices before launching or retrieving any watercraft to ensure they are not bringing aquatic invasives species (AIS) into a lake or carrying AIS out of a lake into another waterbody. This is especially important at Lake Sebago in light of the recent identification of hydrilla. State Parks will be providing additional signage and educational information for boaters at Lake Sebago and surrounding waterbodies in Harriman State Park.

"Aquatic invasive species like hydrilla can pose a significant threat to the health of our lakes and rivers and to the habitat they provide for fisheries," said DEC Deputy Commissioner for Natural Resources Katie Petronis. "With our extensive boat steward program and rapid response plans, DEC has been bolstering current invasive species surveillance, outreach and education and taking actions to address these invaders as quickly as possible to protect our fisheries, wildlife, and local recreational economies into the future."

Research shows that recreational watercraft are a top vector for the transport and introduction of AIS throughout the country. At many State Park locations, watercraft inspection stewards provide education and outreach to many boaters and offer voluntary inspections. State Parks also provides environmental education on aquatic and terrestrial invasives to visitors.

The 310-acre Lake Sebago is the largest lake in Harriman State Park. The name is Algonquian for "big water."

The New York State Office of Parks, Recreation and Historic Preservation oversees more than 250 parks, historic sites, recreational trails, golf courses, boat launches and more, which in 2021 were visited by record 78.4 million people.  For more information on any of these recreation areas, visit, download the free NY State Parks Explorer mobile app or call 518.474.0456. Also, connect on Facebook, Instagram and Twitter.