How to Successfully Control Aquatic Weeds in Lakes and Ponds

One of the most challenging tasks in managing lakes and ponds is the control of unwanted vegetation. Each year in spring and into summer, vegetation management will be the most important task for anyone managing lakes and ponds.

Summer is also when recreational activities such as fishing, swimming, and boating take place on lakes and ponds. If poorly managed, aquatic weeds can develop into dense stands of vegetation that interfere with intended water uses and destroy the natural beauty of lakes or ponds. When their natural beauty is destroyed, most people will avoid using lakes or ponds for recreation.

If aquatic weed problems develop, measures must be taken to reducethe plant population to manageable levels.

The importance ofcontrolling aquatic weeds in lakes and ponds.

Lakes and ponds are vital for our existence and aquatic weeds must be controlled. There are many reasons why lakes and ponds are important and must be managed to keep them free of aquatic weeds.

Here are some of the reasons. Lakes and ponds:

• Are a part of Earth’s ecosystem that contains 0.8% of the globe’s limited freshwater supply.The remaining 99.2% of Earth’s water is marine water and polar ice caps.
• Can be tapped for a variety of industrial and agricultural uses.
• Are important for hydroelectric power generation
• Serve our domestic water supply needs and our aesthetic and recreational purposes.
• Provide a habitat for a variety of wildlife species. 
• Regulate the services of soil formation, biodiversity, groundwater recharge, and flood protection.

At the onset of spring each year, aquatic weeds begin growing, become established, and if not controlled can change the nature of the aquatic habitat. Because they are aquatic weeds, they try to dominate the habitat by displacing indigenous species. Due to their rapid growth, the aquatic weeds can soon become the dominant species in the lake or pond.

What happens when aquatic weeds take over lakes and ponds?

Aquatic weeds in lakes and ponds:

• Block water channels which inhibits irrigation and impedes boat navigation.
• Cause silt buildup.
• Obstruct sight lines.
• Become 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.

What types of aquatic weeds can be found in lakes and ponds?

There are four types of aquatic weeds: algae, emergent, floating, and submerged.

• Algae– lower plant forms with no distinguishable leaf, root, or stem, and often referred to as pond/lake scum, e.g. lyngbya.

• Emergent – grow in shallow water with leaves or stems above the water, e.g., napiergrass.
• Floating – growunattached 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.

How to control each type of aquatic weed.

The most common methods used to control undesirable aquatic weeds are mechanical and chemical.

• Mechanical control is achieved through the use of specially designed tools that can clear aquatic weeds from entire areas or selected spots. However, mechanical methods tend to be laborious and time-consuming.
• Chemical control of aquatic weeds is achieved with EPA-approved aquatic herbicides and algaecides. However, successful control depends on the correct identification of aquatic weeds and closely following the instructions on the herbicide label.

6 Steps for control of aquatic weeds in lakes and ponds

1. Correctly identify the aquatic weed
   • Correctly identifying the aquatic weed will improveunderstanding of the biology and ecology of the species which will helpdetermine how to apply chemical control measures.
2. Select the best pesticide product and formulation that will control the aquatic weed species while causing little to no harm to non-targets and the environment.
   • Ensure that the herbicide or algaecide is registered and approved for use
   • Read the herbicide or algaecide label instructions to ensure that the aquatic weed species can be controlled.
3. Determine what adjuvants are needed to optimize control of the aquatic weed species.
   • Read the herbicide or algaecide label for instructions on using adjuvants
   • Select the adjuvants needed ensuring that they are registered for use in lakes and ponds.Prepare the herbicide or algaecide spray mixture using the guidelines for proper mixing of pesticides.
4. Apply the herbicide or algaecide spray mixture.
5. Evaluate the success of aquatic weed control.
6. Repeat application of herbicide or algaecide spray mixture if necessary, evaluate success, and determine need for further management.

To protect our lakes and ponds and our way of life, we must strive to stop the establishment and spread of aquatic weeds.

Further Reading

• Understanding the Enemy: Pest Biology and Ecology in Aquatics
• Control Invasive Aquatic Plant Species
• What are the Best Practices for Improving Aquatic Management?
• Preventing Algal Blooms from Taking Over Ponds and Lakes
• Tips on How to Use Diquat Herbicide on Lakes and Ponds
• Cattail and phragmites control can be enhanced with Cide-Kick II M
• Limonene: An Environmentally Safe Compound for Pest Control

References

University of Florida, Institute of Food and Agricultural Sciences (UF/IFAS), Center for Aquatic and Invasive Plants. 2021. Most Invasive Aquatic Plants. https://plants.ifas.ufl.edu/manage/[Verified, April 28, 2022].