Late-Season Aquatic Vegetation Management

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Late-Season Aquatic Vegetation Management

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Aquatic vegetation consists of plants that grow in or around water and is a natural part of lake and pond ecosystems. Aquatic vegetation can be found in every lake and pond and there is plenty of good as well as bad that can happen with it.

Contribution of aquatic vegetation to the environment

Aquatic vegetation provides numerous benefits that help sustain habitats and those that rely on it

Besides being aesthetically pleasing plants along the shores of lakes and ponds, aquatic vegetation serves a far more important role. Aquatic plants can enhance the overall health of waterways and provide many positive effects for lakes and ponds. For example, aquatic vegetation can:

  • Absorb excessive nutrients
  • Stabilize lake and pond banks
  • Provide a healthy habitat for fish and other wildlife
  • Provide a food source for fish and wildlife

How about the bad side of aquatic vegetation?

Problems caused by aquatic vegetation

First, some aquatic plant species are recognized, and classified, as weeds. The aquatic weed classifications are algae, emergent, floating, and submerged.

  • Algae – lowest and most primitive plant form with no distinguishable leaf, root, or stem.
  • Emergent – grow in shallow water with leaves or stems above the water, e.g., napiergrass.
  • Floating – grow unattached or rooted, with floating leaves. Most have roots that hang in the water from floating plant parts, e.g., water hyacinth.
  • Submerged – grow in deeper water below, or up to, the surface, e.g., hydrilla.


Second, aquatic systems managers should recognize that a completely weed-free aquatic system is not a biologically healthy.

Third, under some circumstances,a ‘good’ aquatic plant species may grow and behave like a weed.

Fourth, aquatic system management can be very effective when applied with a good understanding of the dynamics of the aquatic ecosystem. In other words, understanding what to do when an aquatic plant ‘goes rouge’

What happens when aquatic vegetation ‘goes rogue’?

Aquatic vegetation in lakes and ponds can become overgrown (go rogue) and the following are some of the things that can happen as a result.

  • Water channels may become blocked which inhibits irrigation and impedes boat navigation.
  • Cause silt buildup.
  • Obstruct sight lines.
  • Become a breeding ground for insects and other undesirable organisms.
  • Interfere with recreational activities, such as fishing, swimming, and boating.
  • Cause water quality issues, foul odor, and unsightly appearance.
  • Cause fish to die off.

The importance of aquatic vegetation management

During the summer months, the likelihood of a ‘surge’ in aquatic vegetation growth is high. Consequently, management efforts during the summer are implemented to maintain a sustainable balance of aquatic plants that sustains or improves the quality of the aquatic environment. Thus, aquatic plants are managed to sustain aquatic life, especially fish, and provide desired aesthetic benefits for human livelihood.

Summer is also the best time for implementing management efforts, such as chemical control of invasive aquatic plants.

Early summer herbicide application to control weedy aquatic vegetation is done in ways that minimize the potential harm to other aquatic life forms, especially fish. If too much vegetation is killed at once, the decomposing plant material ties up the oxygen in the water which reduces the amount available for other aquatic species. Reduced oxygen in water is one of the reasons why fish kills occur.

If aquatic vegetation management is done in late summer or early fall care must be taken to ensure that the decomposing vegetation is not excessive. One strategy is to treat the aquatic system (lake or pond) in sections to spread the decomposition of vegetation in space and time.

Can aquatic plant management be accomplished with late-season chemical applications?

Successful management of emergent aquatic plants has been achieved when herbicides are applied in late summer/early fall season. The key to it is to apply herbicides before the plant goes dormant,which generally occurs before the first frost. The late-season herbicide application on emergent aquatic plants, like phragmites and water hyacinth, is often more successful than mid-summer treatments.

Late-season application of herbicide works well on perennials which reproduce vegetatively via underground structures like rhizomes, tubers, roots, etc. After the first frost occurs, perennial plants begin channeling resources to their reproductive structures. If an effective systemic herbicide is applied to the perennial plant immediately after the first frost, the herbicide will reach the vegetative reproductive structure and kill the plant.

A strategy for late-season aquatic vegetation management with herbicide

  • Select the best herbicide that can be translocated to the vegetative structure,and which will provide the best control of the emergent aquatic plant species. A systemic herbicide like 2,4-D, dicamba, or glyphosate, will be the best option.
  • Select an appropriate adjuvant that will enable the herbicide to spread on the surface of plant leaves and be retained long enough to penetrate the leaf surfaces. For example:
    • Cide Kick™,Cide Kick II™, or Sun Wet™ are nonionic wetting, spreading, and penetrating agents that can be added to a mixture containing a systemic herbicide to improve the control the targeted perennial weed.
  • Make sure you read the herbicide label and follow all recommended instructions to get the best control of emergent aquaticplants.


Further Reading



  • University of Florida, Institute of Food and Agricultural Sciences (UF/IFAS), Center for Aquatic and Invasive Plants. 2021. Most Invasive Aquatic Plants.[Verified, Oct. 12, 2022].

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