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 NCDEQ has designated specific plants as Noxious Aquatic Weeds. The list of noxious aquatic weeds was populated by first adopting all the plants that are federally listed. The list was then expanded by including additional exotic plants that are either known to express invasive behavior in North Carolina or are very likely to become problematic if introduced to North Carolina waters.  The plants designated by NCDEQ as noxious aquatic weeds are written into the North Carolina Administrative Code. 

The Complete List of NCDEQ Noxious Aquatic Weeds - 15A NCAC 02G .0602

The aquatic weeds on the table below are either actively under management or were part of a management project in recent years.

Aquatic Weeds

Common Name	Image	Scientific Name	Web Resources	Distribution Maps	Regulated by NCDA ?
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
Phragmites		Phragmites australis (Cav.) Trin. Ex. Steud	USDA UF/IFAS	EDDMaps USGS
Water Hyacinth		Eichhornia crassipes (Mart.) Solms	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

Control Methods

Once a non-native species has been introduced into a body of water, many control methods are considered based on cost and effectiveness to treat it. Depending on the specific conditions of different water bodies, one method of control might be more desirable than another (e.g. herbicides would be preferable over biological control methods in a river due to the constant motion). Often times more than one method is used to swiftly and efficiently tackle the problem. Below are the methods used by the Aquatic Weeds Control Program:

• Grass Carp are an herbivorous fish native to Asia and are quite effective at eradicating aquatic weeds. They are introduced into bodies of water such as lakes or ponds to help with the treatment of non-native plants. While they prefer invasive plants such as Hydrilla, they don't discriminate and will eat the native vegetation as well. Because of this, sterilized Grass Carp known as Triploid Grass Carp are used to prevent them from reproducing and outcompeting the native fish species. The amount of these Carp stocked is dependent on the specific body of water and is carefully calculated to minimize impact to the native vegetation. After a few years, the 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 this blog post from the Department of Water Resources

• Insects such as Salvinia Weevils and Alligator Weed Beetles are another biological control method used on specific sites to aid in treatment. Unlike Grass Carp, these insects are monophagous meaning they only consume the target plant. Salvinia Weevils are only known to eat Salvinia and Alligator Weed Beetles are known to eat Alligator Weed. These insects have a short lifespan (~2 months), a quick reproduction cycle, and they don't consume a lot of biomass, so they are stocked in large quantities. The use of insects is often used in conjunction with herbicidal treatments to further hinder the spread of invasive plants. The success of this treatment method is not always consistent as these insects need a food source year-round and do not always survive Winter. This can lead to an uptick in infestation of the target plant the following season.    
• Herbicide is a common and efficient method for aquatic weed control that can be used to directly target plants. Different plant species respond to different herbicides at higher or lower concentrations. When creating a treatment plan with aquatic herbicides, the specific herbicide(s) are chosen based on the target weed and environmental conditions of the water body. The concentration of the herbicide is carefully calculated to minimize cost and damage. It is important not to use too much as this can be detrimental to the ecosystem and the public. Between herbicide applications, water samples can be collected and tested to determine the concentration of herbicide that remains in the water months after an application. Depending on the results of the test and the effects on the invasive plants, the amount of herbicide may be adjusted for future applications to change the concentration.
• 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. 

Each of these methods will of course have their respective drawbacks. When creating a treatment plan many of the following are to be considered:

Prevention

The best way to protect your waters is to prevent invasive species from entering all together. Public meetings, online posts, literature, signage, cleaning stations, workshops, and more are all helpful resources that are available to keep the public informed and up to date. Invasive species are often spread by people, so the best way to prevent them is to stay informed, maintain proper practices, and spread the word. If you believe you already have an invasive plant species in your waters, you can report a sighting with Duke Energy's Plant Reporting Tool to help prevent it from spreading. 

Below are some more resources about proper boating practices and methods to prevent the spread of invasive species.

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

Site Assessments

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

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.  

Aquatic vegetation survey reports are linked in the table below:

Comprehensive List of Projects and Project Costs 

• 2024 Aquatic Weed Control Work Plan
• Management activity database

Large-Scale Projects 

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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