Lakes_Content Page_Aquatic Herbicide FAQ

Frequently Asked Questions about Aquatic Herbicide Use in Wisconsin

The DNR often gets questions about why herbicides are used in Wisconsin waters and what protections are in place for people, animals and the environment. To help answer these questions, the DNR, Dept. of Health Services (DHS) and Dept. of Agriculture, Trade and Consumer Protection (DATCP) have collaborated to share the most up-to-date information on aquatic herbicides with you. If you have a question that is not answered below, please reach out to DNRAPMProgram@wisconsin.gov.  

Frequently Asked Questions about Aquatic Herbicide Use in Wisconsin

What are the "weeds" in the water around my dock?
The lake "weeds" around your dock are in fact valuable aquatic plants. These plants provide fish habitat, improve water quality, prevent shoreline erosion and more. Occasionally, these plants may cause problems by limiting navigational access to a lake from the shore. Some plants may be invasive and potentially capable of causing ecologic or economic harm. In these cases, the use of aquatic herbicides is one potential management option that may help alleviate these plant problems.
Why are herbicides used in Wisconsin lakes and rivers?
Aquatic herbicides are used to reduce the abundance of nuisance-causing plant species, to control the spread of invasive species within and amongst waterbodies, and to improve navigational access to lakes and rivers.
How are aquatic herbicides regulated in Wisconsin?
In order to be legally used in Wisconsin, an aquatic herbicide must meet all of the following:
  1. Labeled and registered with the U.S. Environmental Protection Agency’s (EPA) Office of Pesticide Programs.
  2. Registered for sale and use by DATCP.
  3. Permitted under ch. NR 107 by the DNR; and
  4. Applied by a DATCP-certified and licensed applicator, with few exceptions.
Step 1. U.S. EPA’s Office of Pesticide Programs reviews the chemical and label.
The EPA reviews and registers herbicides before sale or use in the United States. The registration process determines potential risk to human health and the environment. The human health assessment evaluates sensitive groups including infants. The assessment includes a risk analysis for both short-term and long-term effects. EPA will register a pesticide if they determine the pesticide use will not "generally cause unreasonable adverse effects." Federal law defines this threshold. The EPA reassesses registered herbicides every fifteen years.
Step 2. DATCP registers herbicides before sale or use in Wisconsin.
DATCP will register most EPA-registered herbicide products for sale and use in Wisconsin. But DATCP will not register an herbicide for use if it is prohibited for sale, use or distribution in Wisconsin, even if it is registered by EPA.
Step 3. DNR reviews ch. NR 107 permits to control aquatic plants and organisms.
Permit application requirements include:
  • A copy of the permit application sent to adjacent landowners.
  • Treatment plans for large-scale control projects (over 10 acres or 10% of the waterbody that is 10 feet or less in depth).
  • Public notice in the local newspaper for large-scale control projects.
  • The proposed herbicide.
  • An analysis of the alternative control strategies.
When reviewing a permit, the DNR considers factors including:
  • Is the proposed herbicide appropriate for the location and target species?
  • What are the likely effects on non-target organisms: fish, native plants, and wildlife?
  • Is there potential for adverse effects on the waterbody?
  • Is there potential for hazard to human health?
After careful consideration, the DNR may:
  • Issue the permit,
  • Issue the permit with conditions, or
  • Deny the permit.
The DNR uses permit conditions to make sure that the herbicide is used responsibly and in line with best management practices for the target plant or specific site conditions. For more information, please read: How does the DNR ensure that herbicides are used responsibly? (below)
Step 4. Applied by a DATCP-certified applicator.
Certified applicators must apply pesticides to Wisconsin waterbodies. An individual must complete a training course and pass a written exam to be certified. Businesses that conduct herbicide application services must also be licensed by DATCP. For more information on certification and licensure see DATCP’s website here.
A person applying an aquatic herbicide does not need to be certified with DATCP if:
  • They are applying a granular product that is not a restricted-use pesticide,
  • The area is less than ¼ acre in size, and
  • The individual applying the herbicide is not "Commercial for Hire."
However, they would still need an approved NR 107 permit from DNR prior to applying any herbicide to the water.
Are herbicides safe?
The distinction between "EPA registered" and the terms "approved" or "safe" is important. Registration by the EPA does not mean that the use of the herbicide poses no risk to humans or the environment. EPA registration means that for use in the U.S., the benefits have been determined to outweigh the risks. Because product use is not without risk, the EPA does not define any herbicide as "safe." It is prudent to minimize herbicide exposure whenever possible. When the EPA registers an herbicide, they set use requirements to minimize risk. These requirements may be found on the herbicide label. The label instructions must be followed exactly any time an herbicide is used. Never use an herbicide for a use not specified on the label.
How does the DNR ensure that herbicides are used responsibly?
The Department of Natural Resources weighs the benefits and risks of chemical applications.
Staff consider:
  • The stated goal on the permit.
  • The potential benefits of using the chemical.
  • The other management activities on the waterbody.
They weigh the benefit of control against:
  • The potential risk to non-target organisms including fish, plants and wildlife.
  • The presence of threatened or endangered species in and around the control site.
  • The potential risk to human health or water quality.
Permits are often conditioned to reduce potential non-target effects by:
  • Adjusting the time of year control takes place to primarily target invasive species.
  • Adjusting the timing of control to avoid potential impacts to spawning fish.
  • Setting thresholds for the total amount of herbicides in the water at any given time.
  • Limiting chemical control around holidays.
  • Encouraging multiple control strategies including chemical, mechanical, manual, and physical control.
When herbicides are used:
  • DNR and DATCP staff may supervise the pesticide application process.
  • The area along the control site is posted with water use restriction signs. These signs must follow DNR and DATCP requirements. They inform water users if there are any use restrictions during and/or after the chemical application.
  • A chemical treatment report is sent to the DNR within 30 days. These reports are public documents. You may search by permit number, waterbody name or applicant name. If you need assistance in finding a record, please reach out to DNRAPMProgram@wisconsin.gov.
How long do the chemicals stay in the water?
The amount of time an herbicide will stay in the water varies considerably depending on the specific product and site. Herbicide concentrations may only be present in the water for a few hours, or for as long as a few months. Each herbicide has different characteristics that affect:
  • Where and how quickly the chemical moves within the water column.
  • How it is broken down (e.g., sunlight, bacteria, water).
  • How long it can be detected in water, sediments, and aquatic organisms.
For more information, please see the individual chemical fact sheets.
Should I let my kids swim in the water?
Water use restriction signs must be posted at public access points to the waterbody for at least one day near an herbicide treatment and sent to shoreline landowners in advance of the treatment. These signs outline what herbicides were used, and what, if any, water use restrictions there are. To minimize your risk of direct exposure, it is wise to stay a safe distance from the control area while herbicide applications are being made. Water use restrictions vary by herbicide but will always be listed on the herbicide label. Potential water use restrictions examples include swimming, fishing, and irrigation. Even after the water use restrictions have been lifted, dilute amounts of herbicide may be present in the water, but EPA has determined that minimal exposure would result from adults or children swimming in dosed waters. To find out how to read an herbicide label, see https://www.epa.gov/pesticide-labels/keep-safe-read-label-first. In general, it is good practice to promptly rinse off with clean water after swimming in a lake or river.
What if I accidentally ingest some of the water while swimming or my pet drinks the water?
You should check boat landings or your dock prior to using the water to see if any water use restriction signs have been posted. If a sign has been posted, read what water use restrictions are listed and follow the instructions. If a water use restriction sign does not list swimming or drinking as a restriction after the water has been dosed with pesticides, then the exposure to the herbicide would be small with no toxic effects.
When assessing the risk posed by swimming in treated water, the EPA considers exposure from accidental swallowing of water, as well as from other routes such as through the skin. Any exposure to herbicide in the water while swimming or through accidental ingestion would be small and would not have toxic effects. Similarly, your pet should not have any side effects from swimming in or drinking treated water, so long as any applicable use restriction period is over.
Are there risks to drinking water?
In Wisconsin, most drinking water supplies come from groundwater, not surface water. Some herbicides product labels require that applications must be a minimum setback distance from any existing drinking water intakes. Private wells are not considered to be intakes, so the setback distance does not apply. Some aquatic herbicides can move through the sediment into the groundwater. However, those that do move through soil are not detected above drinking water thresholds in wells.
Can I eat the fish?
You should review the herbicide label or water use restriction signs to see if there are restrictions on fishing for any amount of time or on fish consumption. If there are no water use restrictions around fishing or fish consumption that does not mean you would not be exposed to the herbicide. It means the amount of herbicide that you might be exposed to is not toxic. A common concern with eating fish from treated water is that the herbicide concentration may be higher in fish tissues than in the water, and therefore exposure may be greater from fish than from exposure to lake water. The EPA registration process evaluates the potential for bioaccumulation in fish, and the degree to which bioaccumulation occurs varies by herbicide.
Can I water my lawn/garden with lake water?
Many of the herbicides used in lakes and ponds are broadleaf herbicides which have the potential to damage garden plants including fruits and vegetables. Some aquatic herbicides may also affect grass. Whether you are watering your lawn or your garden, it is important to follow water usage restrictions to avoid any unintended damage. These irrigation restrictions will be listed on the herbicide label and posted at boat landings, public use areas, and in front of affected properties. The use restrictions vary widely, from no restriction to waiting until 120 days following application. If you are unsure about the herbicide used on the waterbody, the safest option is to use water from your municipal supply or private well to water plants.
How can I find out if an aquatic herbicide treatment is scheduled for a lake, or has occurred recently?
Notices of herbicide applications and the use restrictions of the herbicides used are required to be posted along shore adjacent to a treatment area, as well as at public access points for the day of treatment through the end of the restricted use period. Additionally, landowners adjacent to a treatment area should be sent advance notification of the treatment by mail, email or newsletter. For a large-scale treatment (over 10 acres or over 10% of the area of the waterbody that is 10 feet or less in depth) all landowners around the lake would receive advance notification. These treatments are also posted for public notice in a local newspaper or advertisement page.
How can I be notified in advance of when and where an application will occur, even if I am not adjacent to the treatment area?
If a treatment is over 10 acres or 10% of the waterbody less than 10 feet in depth, the permit application will be posted for public notice in a local newspaper. You may watch for local notices. The DNR will notify any interested person of upcoming applications if they request to be notified in writing each year. To request notification, contact your local DNR aquatic plant management coordinator. 
Why can one person or group of people receive a permit to treat a lake if I don’t want the treatment?
Any individual or group can request a permit from the DNR for a treatment since waterbodies in the state are public property. The DNR is charged with evaluating any proposed treatments to consider the impact on the environment, and permits can be denied. The permitting process requires that all landowners adjacent to the treated area be notified of the treatment prior to sending a permit to the DNR. If you receive the notice and don’t want the treatment to occur, you can send a written request to the applicant and the DNR requesting a public informational meeting. If five or more such requests are received within five days of the notice, the applicant must conduct such a meeting in a location near the waterbody.
What can I do to reduce the need for aquatic herbicide use?
Individuals can help minimize the abundance of nuisance causing aquatic plants and algae by:
1. Implementing best management practices on their property to prevent nutrients from running into the water and by preventing the spread of invasive species.
  • To reduce runoff, eliminate the use of fertilizers adjacent to a waterbody,
  • Rake leaves out of the street and off the lawn,
  • Plant a buffer strip of native vegetation on the shore to reduce erosion and filter water coming off lawns,
  • Create a rain garden to filter and slow down water from driveways or rooftops, or use a pervious option to pave driveways or sidewalks,
  • Use a rain barrel to collect water from rooftops to use to water plants,
  • Encourage your neighbors to follow these best management practices as well.
2. To prevent the introduction of new invasive species and stop the spread of existing invasives, when boating:
  • Remove plants, animals, and mud from your boat when leaving a boat launch,
  • Drain all water from your boat, and
  • Rinse your boat and equipment with hot or high-pressure water or allow to dry for at least five days before moving to another water body.
Where can I find more information about a specific herbicide?
The DNR provides chemical factsheets on each active ingredient permitted in Wisconsin for the management of aquatic plants and control of other aquatic organisms: https://dnr.wisconsin.gov/topic/lakes/plants/factsheets.
The EPA’s risk assessments are available at Pesticides Chemical Search | Chemical Search | Pesticides | US EPA
Additional information can be found with these resources:
Do you have a question about lakes?
If you would like to learn more about water quality, health or water levels please visit our Wisconsin Lakes FAQ page.