What to Expect From an Aquatic Vegetation Treatment?


When you are having your pond or lake treated for aquatic vegetation there can be a lack of experience, misinformation, and general concerns about the project. A professional aquatic biologist, licensed as an aquatic pesticide applicator, can do the job effectively and safely.

How did the plants and algae get in my pond?
Algae and aquatic plants are more common than you might imagine and they can arrive by wind or water entering your pond, or with some help from animals that may be attracted to your pond.  Turtles travel from ditches and streams to find ponds to lay eggs each spring and they have surface area and crevices that can hold seeds or even plant fragments. Birds travel from pond to pond daily and can easily infest a pond with seeds or small plants like watermeal, duckweed, or salvinia. Nutria, beaver, muskrat and otters travel between ponds and their fur makes a nice texture for things to cling to and the moisture assures the seeds and fragments arrive in good health to infest your pond.

If I leave it alone what will happen?
Ponds and certain lake coves and other areas are naturally more prone to aquatic vegetation.  Aquatic plants (native and non-native) and algae infest these areas and in most situations will continue to infest, seed in, spread, and choke a pond or inlet until it becomes unusable. However, there are also good citizen plants that are beneficial and desirable. These plants may need some management but in general will act as a healthy component to the pond or lake. A professional applicator can tell the difference and design a plan to treat undesirable species and protect desirable species of plants.

Are multiple treatments necessary?
For many species and the treatment approach, yes. Vascular plants (roots, stems, leaves, flowers, seeds) after established, will have significant energy built up in the root system, and likely a bed of seeds established in the mud on the floor of the pond. Algae creates seed cells which are harder to penetrate with algaecide and can persist between treatments. Other plants are all invested in what you see growing and not much in seed or roots and these can be remedied almost completely with a single treatment. Some herbicides are made to be applied as a single application and persist for months, providing long term protection. Treatment and control are different from eradication and a practical plan based on the species should be designed.

Will it kill my fish?
A properly applied herbicide or algaecide treatment should not kill fish. There are many stories of copper based algaecides killing fish with improper application as a result of copper toxicity.  Copper can be toxic to fish and other aquatic organisms and proper treatment is based on volume and also the water chemistry, in order to safely and effectively apply it. Also treatment of heavily infested ponds, with large volumes of vegetation can cause an oxygen depletion. The submersed vegetation stops photosynthesising and oxygen production stops. Then as the material degrades in the water, it consumes oxygen through biological processes. All of this is avoidable with a thoughtfully designed plan of treatment.

How long before I see results?
It depends on the vegetation and the herbicide used.

Algaecides affect filamentous algae in 1-2 days, usually will turn brown or white, depending on the treatment, and then degrade over a week to 10 days. Algae reproduces fast and if a pond has a serious infestation with filamentous algae, it may have to be treated several times to get on top of the problem and break the seeding cycle.
Treated planktonic algae (single cell algae/ green water), depending on the level of treatment, will disappear or be reduced in the water column within 48 hours. There are beneficial bacterial treatments that can successfully and safely treat planktonic algae.

Submersed vegetation
Most submersed vegetation will respond rapidly (1 day to 1 week) to treatment and for this reason can also deplete the water of its oxygen supply. Having aeration in place, having a plan to treat the body of water a portion at a time, or treating with a slow acting herbicide can avoid oxygen depletion. Submersed plants also can have substantive tubers/roots, and seed beds that store the potential for reinfestation and these require monitoring and retreatment to achieve good control.

Vascular plants (roots, stems, leaves, flowers, seeds)
Water lilies or cattails are good examples. These generally need enough treatment to enter the root and kill it to prevent the regrowth of new vegetation. Typically the vegetation will turn brown and begin to degrade. These usually regrow slower but monitoring and retreatment is advised.

Herbicides vary in the time that they show results and the speed of time in action. Some herbicides go to work rapidly and are gone in 24 hours, broken down completely. Other systemic herbicides will work over a longer time frame from 10 days to 60 days. This can be a frustrating wait but it is best to ask about the time frame and put it on your calendar to help with your patience, knowing you have a good plan.

If it is dead, when do I quit seeing it?
Submersed aquatic vegetation, waterlilies, and floating plants (duckweed, water lettuce) can take a month to degrade, while cattails and water hyacinth can last for 6 months. This can be affected by the type of herbicide used, and enzymes and beneficial bacteria can be added to assist and speed up this process.

A professional biologist and experienced aquatic applicator can properly identify and assess the need to treat aquatic vegetation in your pond. An effective and safe plan can be developed using chemical, physical, and biological methods to control invasive vegetation in your pond.

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