aquaticsAugust 12, 2021

Tips on How to use Diquat Herbicide on Lakes and Ponds

Brewer International Technical Team

Product Development & Agronomy

Diquat is a fast-acting, non-selective contact herbicide registered by the US EPA for use in aquatic systems and agriculture. To use it in a lake or pond, identify the target invasive plant, identify the desirable species that must be protected, choose the application type that fits the plant’s growth habit, and treat in stages. Always follow the product label.

We often see lakes and ponds as we drive around the country from place to place but probably don’t realize how vital these bodies of water are to our livelihoods. Here you are about to know how to use diquat herbicide for our lakes and ponds.

Much like the air we breathe, lakes and ponds are highly important features of our lives and are mostly used for recreation activities such as swimming, boating, nature viewing, and fishing.

However, before we get too far, what are some important facts about lakes and ponds?

First, lakes and ponds are:

Components of the Earth’s surface water are located in low spots in the countryside where surface water runoff and groundwater seepage can accumulate.
Are a part of Earth’s freshwater supply. Only about 2.5% of Earth’s water is fresh, and most of that is locked in ice caps, glaciers and groundwater. Freshwater lakes hold less than 1% of the world’s fresh water.

Second, lakes are larger and deeper than ponds, and can be natural or artificial. For example:

An artificial lake can be constructed for industrial or agricultural use, for hydroelectric power generation, domestic water supply, or for aesthetic and recreational purposes.
An artificial pond can be constructed for aesthetic and recreational purposes, habitat restoration, architectural reasons, and breeding of fish or other aquatic species.

Some other important functions of lakes and ponds include:

Providing a habitat for a variety of wildlife species.
Regulating the services of soil formation, biodiversity, groundwater recharge, and flood protection

Now that you see how our livelihood is within to lakes and ponds, let’s examine why it is vital that we protect these resources.

Are lakes and ponds threatened?

Yes. Here are four major threats to lakes and ponds.

Human exploitation and development because a growing human population exerts pressure on freshwater ecosystems to maintain livelihoods.
Pollution from chemicals such as pesticides and fertilizers from farms and gasoline and oil from motor vehicles can have negative impacts on aquatic life, wildlife, and humans.
Aquatic invasive plant species are plants that can invade lakes and ponds and become dominant species within the invaded habitat. When this happens, a displacement of beneficial species may happen. Leading to a loss in biodiversity which will affect community structure and ecosystem functioning.
Climate change has resulted in altered timing and amount of water that flows to lakes and ponds. This flow of water to lakes and ponds causes flooding and an increase in the amount of water pollution.

The most challenging and costly threat comes from invasive plant species, especially those that invade aquatic systems.

What are invasive plant species?

Invasive plant species are a unique class of plants that can enter a habitat. They also become quickly established, and change the nature of the habitat. It’s as if the invasive plants sneak in and try and act like they belong in or become ‘owners’ of their new habitat.

As they are establishing, invasive plants are doing everything they can to get rid of native plant species. If you can’t get rid of them, the invasive plants may become the dominant species within the habitat.

Aquatic invasive plant species invade freshwater and marine ecosystems, and some of the most problematic aquatic plants are the ones lake and pond managers encounter most often. They are a major concern for lake and pond managers because of the widespread negative impacts within freshwater ecosystems. Such as loss of recreational opportunities, fish kill, or stunted fish.

Fortunately, research scientists have developed tools to confront the invasive aquatic species and rescue our fragile freshwater ecosystems.

One such tool is diquat herbicide.

Here are some facts about diquat herbicide.

Diquat is a herbicide that is registered by the US Environmental Protection Agency for use in agriculture and aquatic systems. It can control some of the major floating, submersed, and immersed aquatic weeds and some species of algae.
Diquat is a fast acting, non-selective contact herbicide. It will kill a wide variety of plants by disrupting cell membranes and interfering with photosynthesis.
See the product label for water-use restrictions.
Diquat is strongly attracted to silt and clay particles in water. Therefore, it will not be effective in lakes and ponds with muddy water or where plants are covered with silt.

Now that we know a little bit about diquat, let’s see how to use it to control invasive aquatic plants.

Tips on how to use diquat to control invasive aquatic plants

Identify the invasive aquatic plant species targeted for control – this is critical for designing a good plan to manage the invasive plant, and the label will help determine if the plant can be controlled by diquat.
Identify desirable species within the lake and pond – since diquat is non-selective, this is a necessary step to ensure that desirable species are protected. The herbicide label will have information to aid in the identification of aquatic species that can be harmed by diquat.
Determine the type of herbicide application that needs to be made. Which depends on whether the growth habit of the invasive aquatic plant to be controlled is emergent, submerged, or floating.

Necessary Precautions When Applying Diquat To Lakes & Ponds Include:

Bottom sediment’s disturbance must be avoided during treatment, which can happen with an outboard motor. Sediment containing silt and clay particles will tie up the diquat molecules and render the treatment ineffective.
Treat infested lakes or ponds in stages, e.g., ⅓ to ½ of the body of water, to prevent excess amounts of decomposing vegetation. It may result in low oxygen levels in the water. Low oxygen levels can be lethal to fish and other aquatic organisms. Treat in stages as the product label directs. Untreated areas can be treated after the interval given on your diquat product’s label.
Diquat can be toxic. Wear the protective equipment listed on the diquat product label and SDS.

Diquat on lakes and ponds: quick answers

Is diquat selective?

No. Diquat is a non-selective contact herbicide, so identify the desirable species in the water body before treating. The herbicide label has information to help identify aquatic species that can be harmed by diquat.

Why treat a lake or pond in stages?

Treating one-third to one-half of the water body at a time helps prevent excess decomposing vegetation, which may lower oxygen levels. Low oxygen levels can be lethal to fish and other aquatic organisms. Treat in stages as the product label directs.

Why does muddy water matter?

Diquat is strongly attracted to silt and clay particles in water, so it will not be effective in lakes and ponds with muddy water or where plants are covered with silt. Avoid disturbing bottom sediment during treatment.

Can adjuvants improve diquat control?

Selecting the best surfactant or adjuvant can help maximize herbicide efficacy. See the adjuvant options in the section below.

Use adjuvants to improve control

Select the best surfactant and/or adjuvant to maximize herbicide efficacy and invasive aquatic plant species control.

For floating plants use Cide-Kick®.
- Cide-Kick® is a d-limonene-based wetting agent, activator and protectant, compatible with many aquatic and terrestrial herbicides, insecticides and other pesticides. A jar test is recommended before tank-mixing.
- Cide-Kick® helps herbicide uptake by breaking down the waxy cuticles on leaf surfaces and penetration of the bud and bark area.
For more information on Cide-Kick®, read Control Invasive Aquatic Plant Species.

For additional information on managing aquatic plants, check out the following blogs:

References

United States Geological Survey (USGS). Lakes and Reservoirs. https://www.usgs.gov/water-science-school/science/lakes-and-reservoirs. Accessed, November 3, 2026.
U.S. Geological Survey (USGS). Where is Earth’s Water? https://www.usgs.gov/special-topics/water-science-school/science/where-earths-water. Accessed, November 5, 2026.
Wisconsin Department of Natural Resources (WDNR). Diquat Chemical Fact Sheet (January 2018). https://apps.dnr.wi.gov/swims/Documents/DownloadDocument?id=158277108. Accessed, November 5, 2026.

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