Hydrilla

Hydrilla (Hydrilla verticillata) is a highly destructive, nonnative aquatic plant found on both the Federal Noxious Weed List and the N.C. Department of Environmental Quality’s Aquatic Weed List. Hydrilla creates nearly impenetrable mats of stems and leaves of the surface of lakes, rivers and other waterways. It crowds out native vegetation, reduces recreational opportunities, and ultimately can harm fish and other aquatic organisms, as well as bird species. The plant also can clog intakes in rivers and reservoirs that are used for drinking water supplies and irrigation. It is considered one of the worst aquatic weeds in the United States. Hydrilla is also known as water thyme, Florida elodea, Wasserquirl and Indian star-vine.

 

Hydrilla can reproduce in four different ways; fragmentation, tubers, turions, and seed:

  • Fragmented pieces of hydrilla that contain at least one node or whorl are capable of sprouting into a new plant.
  • The tubers (roots) of hydrilla are formed on the rhizomes (underground stem) and each one can produce 6,000 new tubers.
  • Turions (buds) formed in the leaf axils of the plant can break off, settle in the sediment, and sprout into a new plant.
  • Seed production is mostly used for long distance dispersal by means of ingestion by birds.

 

Native to parts of Asia, Africa, and Australia, it was first introduced to Florida in the 1950s through the aquarium trade. By the 1970s, the plant had invaded every major drainage basin in Florida. Currently, hydrilla has become established from Florida to Connecticut and west to California and Washington, with the most severe occurrences being found in the Gulf and South Atlantic States. In North Carolina, hydrilla is considered the number 1 invasive aquatic species. It is found in various waters throughout the state, from the mountains to the coast, in reservoirs, natural lakes, rivers, and coastal sounds.

 

Hydrilla Management Efforts

Harris Lake

Harris Lake is a reservoir in New Hill that covers 4,100 acres in southwestern Wake County and southeastern Chatham County. Hydrilla was first reported in Harris Lake in 1988. In September 2018, the Division of Water Resources’ (DWR) Aquatic Weed Control Program conducted a submerged aquatic plant survey at Harris Lake that identified 232 acres of hydrilla. Harris Lake is a source population for the spread of hydrilla to other waterbodies in our state, where the long-term environmental and economic impacts can be substantial. To reduce the risk of hydrilla spreading beyond Harris Lake, DWR plans to stock sterile grass carp to control hydrilla and treat around boat ramps with herbicides to reduce the chance of it spreading to other waterbodies on boats, boat trailers or other equipment. In conjunction with DWR, the N.C. Wildlife Resources Commission is implementing a five-year aquatic habitat enhancement project to establish approximately 30 acres of artificial and natural structures and approximately one acre of founder colonies of native vegetation. Read more on the Harris Lake Habitat Plan page.

Eno River

Hydrilla was first observed in the main stem of the Eno River in 2005 and has since infested over 20 miles of river in Orange and Durham counties. In 2013, the formation of the Eno River Hydrilla Management Task Force created a partnership between multiple government agencies, North Carolina State University, and non-profit organizations to address the growing concern over the infestation. The result of this collaboration was the installation of an herbicidal drip system that releases a low concentration of fluridone into the river during hydrilla’s growing season, beginning in the spring and continuing into the early fall months. Read more about the effects of hydrilla removal on fish and crayfish communities in the Eno River. (PDF)

 

How Can You Help

Carefully clean all equipment, such as boats, trailers, waders, boots, float tubes, and fins

Rinse all mud and debris from equipment and wading gear, and drain water from boats before leaving the area where you’ve been fishing. Careful cleaning reduces the risk of spreading hydrilla and other aquatic nuisance species. Remember to rinse your equipment thoroughly after using bleach to prevent this chemical from entering bodies of water.

Hydrilla Frequently Asked Questions (coming soon!)