Aquatic Weed Control Program

1. Respond to localized infestations to mitigate the long-term economic and environmental impacts that noxious aquatic weeds impose.
2. Reduce the frequency of aquatic weed introductions through education and public awareness.

The philosophy of the program applies to aquatic weed infestations of all sizes. Large-scale projects can be complex and challenging. They may span jurisdictions and require the development of partnerships.  Aquatic weed control projects may involve federal, state and local governments as well as non-government organizations and private landowners.  The program often serves as a major contributor of funding and provides leadership on large-scale projects. Benefits are realized by offering assistance for small-scale projects as well. Allowing aquatic weeds to persist and spread throughout our waterways only exacerbates the problem.

The NC Aquatic Nuisance Species Management Plan provides a detailed explanation of why aquatic weeds are problematic, pathways of introduction and associated laws.

For Public Waters, This Program Can Provide:

• Financial Assistance
• Technical Assistance
• Operational Support
• Aquatic Plant Identification
• Treatment Recommendations

Financial assistance and operational support are in the form of cost-share arrangements and are available to Counties, Municipalities, Soil & Water Districts, Drainage Districts, Public Utilities, and other government agencies.  

Program staff provide a range of fieldwork services including site assessments, aquatic vegetation surveys and aquatic weed management operations.  To provide these services, the program utilizes specialized equipment.  Staff are trained on this equipment and have aquatic herbicide applicator licenses.

How to Apply for Financial Assistance:

• A telephone call, letter or email may serve as the initial communication.  Be prepared to describe the problem in detail.
• Program staff will need to conduct a site visit in most circumstances.
• Submit a grant application.  Download application form.
• Applications must be received no later than October 15 the year before the project begins.
• Applications will be considered for inclusion in the work-plan for the following year.

For Private Waters, This Program Can Provide:

• Technical Assistance
• Aquatic Plant Identification
• Recommend Treatments

Private landowners can also contact their county offices of the Agricultural Extension Service for further assistance.

The N.C. Department of Environmental Quality has designated specific plants as "Noxious Aquatic Weeds".  The list was populated by first adopting all the plants that are Federally listed noxious aquatic weeds and then built on that by including other exotic plants that express invasive behavior in North Carolina. 

• All noxious aquatic weeds recognized by NC DEQ

Common Name	Image	Scientific Name	Web Resources	Distribution Maps	Regulated by NCDA&CS
Alligatorweed		Alternanthera philoxeroides (Mart.) Griseb	USDA UF/IFAS	EDDMaps USGS
Brazilian Waterweed Anacharis		Egeria densa Planch	USDA UF/IFAS	EDDMaps USGS
Brittleleaf Naiad		Najas minor All.	USDA	EDDMaps USGS
Creeping Water Primrose		Ludwigia hexapetala (Hooker & Arnott) Zardi.	USDA UF/IFAS	EDDMaps USGS	YES
Eurasian Watermilfoil		Myriophyllum spicatum L.	USDA UF/IFAS	EDDMaps USGS	YES
Giant Salvinia		Salvinia Molesta Mitch	USDA UF/IFAS	EDDMaps USGS	YES
Hydrilla		Hydrilla verticillata (L.f.) Royle	USDA UF/IFAS	EDDMaps USGS	YES
Parrot Feather		Myriophyllum aquaticum (Vell.) Verdc.	USDA UF/IFAS	EDDMaps USGS
Common Reed		Phragmites australis (Cav.) Trin. Ex. Steud	USDA UF/IFAS	EDDMaps USGS
Purple Loosestrife		Lythrum salicaria L.	USDA UF/IFAS	EDDMaps USGS	YES
Water Hyacinth		Eichhornia crassipes (Mart.) Solms	USDA UF/IFAS	EDDMaps USGS
Water Lettuce		Pistia stratiotes L.	USDA UF/IFAS	EDDMaps USGS

Problems Associated with Aquatic Weeds

• Divert water flows causing erosion and flooding.
• Impede recreational activities like swimming, fishing, boating, and water sports.
• Displace native vegetation which can alter community structure and degrade ecological functions.
• Form dense growths that become navigation hazards.
• Clog water intake systems of industries, municipalities and irrigators.
• Create/expand breeding habitat for mosquitoes and other pests.

Aquatic weeds become more difficult and expensive to control if ignored -- rapid response to developing infestations can reduce the damage caused by noxious weeds and the cost of controlling them.

For more details read Economic & Environmental Impacts of NC Aquatic Weed Infestations

NC Wildlife Commission's Prevention Methods for the Spread of Aquatic Nuisance Species

NC Wildlife Commission's Boating Ramps

For more information about how to Stop Aquatic Hitchhikes, read our Brochure 

Control Methods

• Grass Carp are effective at eradicating aquatic weeds as they consume most aquatic vegetation. Grass Carp are typically used in lakes and ponds instead of rivers as flowing rivers tend to push the carp into larger bodies of water (i.e. lakes and ponds). Sterilized Grass Carp are introduced so they can feed on vegetation without reproducing and outcompeting native fishes. After a few years, the sterile carp will die out and allow for the native species to continue to flourish as native vegetation returns in place of the invasive weeds.
• For more information on Grass Carp, visit the NC Wildlife Commission Resources Website
• Insects such as Salvinia Weevils and Alligatorweed Beetles are often used at treatment sites as a more natural and site-specific control method. Unlike Grass Carp, these insects tend to only consume the intended target plant. Since insects have a quick reproduction cycle, the population of these insects can grow exponentially and increase the rate of control over time. The success of this treatment method is not always consistent and, unfortunately, these insects do not always survive Winter. This can lead to an uptick in infestation of the target plant the following season. 
• Herbicide is a common method for aquatic weed control as it is efficient and can be used to directly target plants without introducing a species that native fish will have to compete with for resources. Different plant species require different herbicides and higher or lower concentrations of the herbicides to achieve the desired outcome. It is also important to not use over-concentrated herbicide as this could impact native plant and animal species as well. Between herbicide applications, a sample of water is taken and tested to determine the concentration of herbicide that remains months after an application. Depending on the results of the test and the effects on the invasive plants, the concentration and amount of herbicide may be adjusted for future applications.
• Harvesting (Physical removal) of invasive plants has proved ineffective and arduous. Some species, such as Hydrilla, are able to survive and reproduce via fragmentation, so if even a few fragments are not removed, the infestation will spread and flourish again.
• Water Drawdown is sometimes used for aquatic weeds such as Giant Salvinia or to survey sites, but it is overall an ineffective control method as ponds and lakes can only have so much of the water drained without causing permanent adverse effects to the ecosystem. Some species of aquatic weeds are also able to survive droughts for extended periods of time. Artificial droughts are therefore used more for surveying and site maintenance than for weed control. 

Site Assessments and Aquatic Vegetation Surveys

Conducting a site assessment is one of the first steps of an aquatic weed management project.  Site assessments identify what species of plants are present and focus on things that are necessary for project planning, such as determining access points and water uses.  Examples of water uses are irrigation, recreation (swimming, fishing, etc.) and municipal water source.  If noxious aquatic weeds are present, they will be documented, and both the size and severity of the infestation will be estimated.  Aquatic weeds that float on the surface of water (e.g., Water Hyacinth and Giant Salvinia) and aquatic weeds that grow up and out of the water (referred to as “immersed” or “emergent plants”, such as Alligatorweed and Water Primrose) are easy to observe. The size of the infestation is typically estimated by visual reconnaissance, or by using a handheld GPS device.  GIS software is also a good tool for estimating size and describing the site. Aquatic weeds that are rooted in the bottom (referred to as “submersed” plants, such as Hydrilla and Watermilfoil) are not as easy to observe.  Estimating the size and severity of a submersed aquatic weed infestation is difficult.  Turbid or tannic water conditions makes this task even more challenging, and the use of specialized equipment is often required.

Aquatic vegetation surveys, similar to site assessments, document noxious aquatic weeds (if present at the site).  Think of an aquatic vegetation survey as an inventory of plants.  The survey identifies what plants are present and where those plants are growing. Depending on the goal, the survey may inventory floating plants, emersed plants, and submersed plants.  Regardless of scope, the survey is a snapshot and can serve as a baseline.  Surveys provide critical information to environmental managers.  Information which is used for aquatic weed project planning and is also used to track project progress.

Aquatic vegetation surveys are conducted annually for many of the program’s Hydrilla management projects.  The program has adopted a survey methodology which involves the collection of two sets of data:  physical sampling and remote sensing. Physical sampling is conducting with a metal rake.  The rake collects vegetation from the bottom.  Sample points are pre-determined (not random).  Vegetation collected via physical sampling allows the surveyor to observe and record the species of plant(s) present.  Remote sensing is conducted with a recording fathometer device, which leverages SONAR technology and GPS technology. The device is mounted on a boat. The operator tracks the shoreline and typically includes the entire littoral zone.  Track lines are adjusted based on site conditions.  The two sets of data are analyzed. This methodology generates maps that show what species of aquatic vegetation was detected, where the vegetation occurs and the relative density.  The outcome of the survey also estimates the total area occupied by each species of vegetation.  

Comprehensive List of Projects and Project Costs 

• 2023 Aquatic Weed Control Work Plan
• Management activity database

Large-Scale Projects 

Lake Norman

Lake Waccamaw

Aquatic vegetation survey reports are linked in the table below:

If you need help with controlling or managing aquatic plants, please contact:

The following links will provide more information about the program, aquatic vegetation identification, and aquatic weed management: 

Local Resources 

• North Carolina Cooperative Extension Service
• North Carolina Invasive Plant Council 
• North Carolina State University- Aquatic Plant Management
• North Carolina State University- Integrated Pest Management
• 2019 North Carolina Agricultural Chemicals Manual: Chemical Weed Control
• North Carolina's Aquatic Nuisance Species Management Plan, Updated October 1, 2015

Aquatic Plant ID and Management Guides

• Biology and Control of Aquatic Weeds
• Univ. of Florida IFAS Extension
• Habitattitude 

Aquatic Plant Field Guide 

• Aquatic & wetland plants of SC
• AquaPlant