Aquatic Herbicides and Surfactants: What they are and how they are used

Freshwater ecosystems are a vital resource for all forms of life on Earth. Consisting of lakes ponds, rivers, streams, springs, bogs, and wetlands, freshwater ecosystems provide essential resources that allow plant and animal species to thrive. Therefore, we must protect freshwater ecosystems at all costs from possible threats.

One major threat is weedy and invasive aquatic plants.

On one hand, there are numerous freshwater ecosystems plants which are essential for a variety of ecosystem functions. On the other hand, there are some plants that are weedy, provide little to no benefit to the ecosystem, and sometimes invade and negatively impact other freshwater habitats.

To prevent the proliferation of weedy and invasive aquatic plants within freshwater ecosystems, aquatic herbicides and surfactants are applied.

What is an aquatic herbicide?

Aquatic herbicides are registered with the US Environmental Protection Agency (EPA) for control of unwanted plants in aquatic ecosystems, including freshwater ecosystems. Aquatic herbicides are used to:

• Reduce the abundance of weedy and invasive plantsin order to prevent their establishment and spread to new water bodies.
• Control nuisance plant and algae growth that can pose a hazard to swimmers, and other recreational activities.
• Help maintain a healthy native plant community that is beneficial for fish and other aquatic organisms.
• Improve navigational access to lakes and rivers.

There are seventeen active ingredients that have been registered by the US EPA for use in aquatic systems. These active ingredients may be formulated and sold as aquatic herbicidesunder a variety of trade names.

What is an aquatic surfactant?

A surfactant, or surfaceactingagent, is a class of adjuvant comprised of chemical compounds that improve the emulsifying, dispersing, spreading, wetting, or other surface-modifying properties of liquids.

An aquatic surfactant can be used in freshwater ecosystems because itis not harmful to aquatic life forms.

When added to an herbicide spray solution, an aquatic surfactant enhances the control of unwanted plants, compared to when no surfactant is used.

Why is it necessary to apply an aquatic herbicide in a freshwater ecosystem?

First – freshwaterecosystems are vital to our existence and must be protected. Why, because they:

• Support a wide range of organisms, including microorganisms, invertebrates, insects, plants, and fish.
• Comprise less than 1% of the Earth’s surface and contain 0.009% of Earth’s water.
• Are continually threatened by:
  • Human exploitation and development
  • Pollution
  • Climate change
  • Invasive species

Second –weedyand invasive aquatic plants are a constant threat to freshwater ecosystems and must be addressed. Why? Because they can:

• Enter a habitat, quickly become established, and change the nature of the habitat.
• Replace native plant species within the habitat.
• Become the dominant species within the habitat with an ability to spread into new areas,if nothing is done to get rid of them.

Other ways weedy and invasive aquatic plants can impact freshwater ecosystems include:

• Loss of recreational opportunities.
• Extreme oxygen depletion and pH changes that lead to stunted fish populations and/or fish kills.
• Restrictions to water-flow leading to flooding.
• Restrictions to navigation.
• Habitat destruction.
• Reduction in species diversity and richness.
• Reduction in property values.

Third – useof aquatic herbicide is the most efficient way of managing invasive aquatic plants in freshwater ecosystems.

How do you use aquatic herbicides?

Steps to follow when using aquatic herbicide:

1. Identify the weedy and invasiveaquatic plant you are seeking to manage and make sure it is listed on the label as one that can be controlledby the aquatic herbicide. Make sure to read the pesticide label carefully.

1. Select the technique you will use to apply the aquatic herbicide based upon the type of aquatic plant species. Specifically, aquatic plants can be:
   1. Emersed – aquatic plants growing in shallow water with leaves and stems above the water’s surface.
   2. Floating – growing unattached or rooted with floating leaves.
   3. Submersed – growing entirely below and up to the water’s surface.
2. Select the best surfactant that is labeled for use in aquatic systems to provide the best control of the weedy and invasive plants to be controlled.

Are aquatic herbicides safe for fish?

Aquatic herbicides that are registered with the US EPA are safe for fish and other aquatic life forms as long as they are used according to label instructions.

However, when fish kill happens after an aquatic herbicide has been applied, it may be due to other factors. For example, after applying aquatic herbicides, too much plant vegetation may die and rapidly decompose. When plant vegetation decomposes in water it depletes oxygen that fish need to survive leading to fish kill. 

When should aquatic herbicides be applied?

• The best time to apply aquatic herbicides is spring when plant vegetation is still low and the potential for fish kill is low.
• The worst time to apply aquatic herbicides in freshwater bodies is between summer and early fall. This is the period when plant vegetation is highest in freshwater bodies. When too much plant vegetation dies in a short time, it may rapidly decompose and use up all the oxygen in the water, leading to fish kill.

What is the best aquatic herbicide surfactant for ponds?

First, check the label. If the label states that surfactants are needed, then one (or more) should be added.

Second, make sure to use a surfactant that is registered for use in aquatic systems. For example:

• Cide-Kick® – a nonionic wetting agent, activator, and penetrant. It helps uptake of herbicides by breaking down the waxy cuticles on leaf surfaces.
• Brewer 90-10® – a low-foam nonionic spreading and activating agent. It helps reduce the surface tension of spray droplets which enables more effective herbicide uptake for improved control.
• Sunenergy®– a nonionic wetting and penetratingagent. It helps herbicides penetrate leaf surfaces of hard to control species.
• Visit Brewer International for more information on surfactantsregistered for use in ponds and other freshwater bodies.

Further reading

• Ten Problematic Aquatic Plants to Watch in 2022
• Brewer 90-10 Surfactant for Excellent Vegetation Management
• I’Vod – A Superior Spray Drift Control Adjuvant
• What Are the Best Practices for Improving Aquatic Management?
• Understand the Enemy: Pest Biology and Ecology in Aquatics
• Control Invasive Aquatic Plant Species

References

• University of Florida/IFAS Center for Aquatic and Invasive Plants (2017).https://plants-archive.ifas.ufl.edu/manage/developing-management-plans/chemical-control-considerations/herbicides-registered-for-use-in-florida-waters/.Verified: Apr. 25, 2022.