Croton Hydrilla Project
Croton Hydrilla Project Background: The aquatic invasive plant, Hydrilla verticillata, is one of the most difficult weeds to eradicate in the United States. It is a federally listed noxious weed and was prohibited in New York in spring 2015 (6 NYCRR Part 575). It was discovered in the Croton River in October 2013 by a New York Botanical Garden survey team conducting a rare plant survey. In autumn 2014 an aquatic plant survey was conducted in the Croton River and Bay area to delineate the extent of the Hydrilla infestation. (link to report here)
Hydrilla has been found in several additional locations in New York: Erie County, Kings County, Monroe County, Nassau County, Orange County, Suffolk County, and Tompkins County. Many of the infestations are in small, isolated ponds. The infestations in Erie County and Tompkins County are found in larger waterbodies connected other waterways, while Westchester County has the only infestation found in a tidal system. Natural History:
Two biotypes of Hydrilla verticillata are found in the United States: dioecious and monoecious. In dioecious Hydrilla individual plants have either male or female flowers, but not both. Only female plants have been found in the United States. This particular biotype is native to India. Monoecious Hydrilla plants have both male and female flowers and are more tolerant of colder temperatures. This biotype is native to Korea.
Hydrilla easily breaks apart into plant fragments that can be carried to new locations by water currents. These fragments can sprout roots and grow into new populations. In addition, Hydrilla produces turions – green overwintering buds that grow where leaves attach to stems. These buds break off and can be carried to a new location to produce a new population the next growing season. Hydrilla also produces tubers at the end of roots which overwinter in the sediment and remain viable and grow into new plants for seven to ten years.
A Hydrilla infestation in the Croton River threatens the Hudson River and its tributaries as fragments, turions, and tubers can make their way into the river system with the movement of the tide. Identification:
Hydrilla is very similar in appearance to native elodea (Elodea canadensis) and invasive Brazilian elodea (Egeria densa). All of these plants have a central stem around which leaves wrap (whorl). It is the number of leaves per whorl and the structure of the leaves that helps to distinguish the different species. Native elodea usually has three leaves per whorl, while Brazilian elodea and Hydrilla have more than three. Brazilian elodea has a very bushy appearance because here is little space between whorls of leaves and each leaf is up to 2 cm long (slight less than an inch in length). Hydrilla leaves are shorter and have serrated edges and a serrated mid-rib. Tubers would be a definitive identifier, but can be hard to find. 1
Hydrilla-Elodea image: Center of Aquatic and Invasive Plants, University of Florida, IFAS
2
Native elodea (American waterweed)
en.wikipedia.org
Brazilian elodea
Les Mehrhoff, University of Connecticut, Bugwood.org
3
Hydrilla
Robert Vidéki, Doronicum Kft., Bugwood.org
Impacts: Hydrilla grows very quickly, producing mats of vegetation that initially grow along the bottom of lakes and rivers. The plant will then grow up to the water surface producing dense mats of vegetation several feet deep. These mats outshade and displace native plants that provide food and shelter to native insects and young fish. They eliminate waterfowl feeding areas and fish spawning sites. Hydrilla disrupts waterflow in reservoirs and drainage in irrigation canals and decreases dissolved oxygen in the water which results in fish kills. The size and weight of sport fish are also reduced in areas infested with Hydrilla.
Hydrilla’s dense mats of vegetation can prohibit boating, swimming, and fishing. Economies that rely on tourist dollars from recreational use of lakes and ponds that become infested can suffer serious losses in income. Control and management of hydrilla are expensive and long-term. An infestation of Hydrilla can also reduce the value of waterfront property and, potentially, propertyowners could incur part of the control costs. Hydrilla can be very expensive to control and once established it is not always possible to eradicate. Its tubers can overwinter and remain viable (produce new plants) for seven to ten years. Control Options: Manual- Handpulling
4
Mechanical – Benthic matting
Chemical – Use of herbicides such as fluoridone, endothall, or copper Biocontrol – None available at this time Update on Croton infestation:
Aquatic plant survey conducted on Croton River 2014 Allied Biological, Inc. conducted an aquatic plant survey of the Croton River and Bay area in 2014 and found widespread presence of Hydrilla which was dense in certain areas. To see the full report please click here Aquatic plant survey in Hudson River and its tributaries August – October 2015 Allied Biological, Inc. performed an aquatic plant survey at more than 40 sites along the Hudson River north and south of Croton. In addition, several lakes in Orange, Westchester, and Putnam County were surveyed by the US Military Academy staff, the volunteer monitoring team Hydrilla Hunters, and Office of Parks, Recreation, and Historic Preservation. No hydrilla was found. Dye study October 2015 Allied Biological, Inc., SePRO, North Carolina State University, and the U.S. Army Corps of Engineers conducted a dye study to assess the flow dynamics of the Croton River to better inform future decisions about managing Hydrilla (see picture gallery here). The Croton River Task Force assisted with preparation for this study by collecting bathymetric data in the tidal portion of the river Resources: New York State Invasive Species Clearinghouse http://www.nyis.info/?action=invasive_detail&id=16
Cayuga Hydrilla Task Force http://ccetompkins.org/environment/aquatic-invasives/hydrilla/fighting-hydrilla-in-thecayuga-lake-watershed/hydrilla-task-force-of-the-cayuga-lake-watershed
Western NY Hydrilla Project http://erie.cce.cornell.edu/invasive-species/wny-hydrilla-project 5
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Hydrilla has been found in several additional locations in New York: Erie County, Kings County, Monroe County, Nassau County, Orange County, Suffolk County, and Tompkins County. Many of the infestations are in small, isolated ponds. The infestations in Erie County and Tompkins County are found in larger waterbodies connected other waterways, while Westchester County has the only infestation found in a tidal system. Natural History:
Two biotypes of Hydrilla verticillata are found in the United States: dioecious and monoecious. In dioecious Hydrilla individual plants have either male or female flowers, but not both. Only female plants have been found in the United States. This particular biotype is native to India. Monoecious Hydrilla plants have both male and female flowers and are more tolerant of colder temperatures. This biotype is native to Korea.
Hydrilla easily breaks apart into plant fragments that can be carried to new locations by water currents. These fragments can sprout roots and grow into new populations. In addition, Hydrilla produces turions – green overwintering buds that grow where leaves attach to stems. These buds break off and can be carried to a new location to produce a new population the next growing season. Hydrilla also produces tubers at the end of roots which overwinter in the sediment and remain viable and grow into new plants for seven to ten years.
A Hydrilla infestation in the Croton River threatens the Hudson River and its tributaries as fragments, turions, and tubers can make their way into the river system with the movement of the tide. Identification:
Hydrilla is very similar in appearance to native elodea (Elodea canadensis) and invasive Brazilian elodea (Egeria densa). All of these plants have a central stem around which leaves wrap (whorl). It is the number of leaves per whorl and the structure of the leaves that helps to distinguish the different species. Native elodea usually has three leaves per whorl, while Brazilian elodea and Hydrilla have more than three. Brazilian elodea has a very bushy appearance because here is little space between whorls of leaves and each leaf is up to 2 cm long (slight less than an inch in length). Hydrilla leaves are shorter and have serrated edges and a serrated mid-rib. Tubers would be a definitive identifier, but can be hard to find. 1
Hydrilla-Elodea image: Center of Aquatic and Invasive Plants, University of Florida, IFAS
2
Native elodea (American waterweed)
en.wikipedia.org
Brazilian elodea
Les Mehrhoff, University of Connecticut, Bugwood.org
3
Hydrilla
Robert Vidéki, Doronicum Kft., Bugwood.org
Impacts: Hydrilla grows very quickly, producing mats of vegetation that initially grow along the bottom of lakes and rivers. The plant will then grow up to the water surface producing dense mats of vegetation several feet deep. These mats outshade and displace native plants that provide food and shelter to native insects and young fish. They eliminate waterfowl feeding areas and fish spawning sites. Hydrilla disrupts waterflow in reservoirs and drainage in irrigation canals and decreases dissolved oxygen in the water which results in fish kills. The size and weight of sport fish are also reduced in areas infested with Hydrilla.
Hydrilla’s dense mats of vegetation can prohibit boating, swimming, and fishing. Economies that rely on tourist dollars from recreational use of lakes and ponds that become infested can suffer serious losses in income. Control and management of hydrilla are expensive and long-term. An infestation of Hydrilla can also reduce the value of waterfront property and, potentially, propertyowners could incur part of the control costs. Hydrilla can be very expensive to control and once established it is not always possible to eradicate. Its tubers can overwinter and remain viable (produce new plants) for seven to ten years. Control Options: Manual- Handpulling
4
Mechanical – Benthic matting
Chemical – Use of herbicides such as fluoridone, endothall, or copper Biocontrol – None available at this time Update on Croton infestation:
Aquatic plant survey conducted on Croton River 2014 Allied Biological, Inc. conducted an aquatic plant survey of the Croton River and Bay area in 2014 and found widespread presence of Hydrilla which was dense in certain areas. To see the full report please click here Aquatic plant survey in Hudson River and its tributaries August – October 2015 Allied Biological, Inc. performed an aquatic plant survey at more than 40 sites along the Hudson River north and south of Croton. In addition, several lakes in Orange, Westchester, and Putnam County were surveyed by the US Military Academy staff, the volunteer monitoring team Hydrilla Hunters, and Office of Parks, Recreation, and Historic Preservation. No hydrilla was found. Dye study October 2015 Allied Biological, Inc., SePRO, North Carolina State University, and the U.S. Army Corps of Engineers conducted a dye study to assess the flow dynamics of the Croton River to better inform future decisions about managing Hydrilla (see picture gallery here). The Croton River Task Force assisted with preparation for this study by collecting bathymetric data in the tidal portion of the river Resources: New York State Invasive Species Clearinghouse http://www.nyis.info/?action=invasive_detail&id=16
Cayuga Hydrilla Task Force http://ccetompkins.org/environment/aquatic-invasives/hydrilla/fighting-hydrilla-in-thecayuga-lake-watershed/hydrilla-task-force-of-the-cayuga-lake-watershed
Western NY Hydrilla Project http://erie.cce.cornell.edu/invasive-species/wny-hydrilla-project 5
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