Controlling pond weeds in large ponds takes a degree of expertise and intensive management. Weeds can grow under, on, or out of the water. When populations of invasive plants exist it can interfere with the fish population, give the water a funny smell, and cause other imbalances in the farm pond ecosystem. Plankton are the only inherently beneficial forms of plant life in a farm pond. Other plants such as floating weeds, submerged weeds, and emergent weeds, are undesirable.
Removal of these nuisances can be daunting but is necessary. Mechanical removal is the first way a pond weed problem can be dealt with. This can involve the use of a cutter to maintain a weed free shoreline. A cutter can sometimes be used on semi submerged weeds such as Cattails. This is because if you cut them off under the water line they will not survive. Mowing and pulling a weed is an effective killer as well. Persistence is required with this method but you will see the fruits of your labor in the same growing season. Another tactic is to fill in or remove any parts of the pond that are less than 3 feet deep.
Biological control of pond weeds is another option. This method entails introducing a living population into the pond that is capable of controlling the undesired weeds. Usually this organism is a type of plankton that will cloud the water and make it hard for the plants to survive because of lack of sunlight and photosynthesis. Inert dies can be poured into the water as well in order to block the sunlight from reaching the weeds. This method is not effective if the plants are on the surface of the pond or growing at a depth of less than two feet. A larger organism, like a grass carp, can be released into the environment. These fish are larger vegetation consumers.
Chemical control is the most common way to control the problem. There are three basic things to consider when choosing which chemical will be most effective. The first is the time of year that you want to apply the substance. Many chemical products will not be effective throughout the summer and need to be applied early in the growing season. The kind of plant needs to be identified also. There is usually a specific killer for specific vegetation. Sometimes certain weeds, like Cattail, have chemicals that are being continually developed.
Lastly, what the water is used for is a consideration. Many chemicals are not suitable for fishing, swimming, or feeding livestock. Some even have restrictions about using the source as irrigation or spray water. Labels on the chemical are required to address this topic thoroughly. No adequate aquatic herbicide has been approved that does not have restrictions.
New chemical products as well as mechanical and biological products and techniques are being introduced all the time. Choosing which ones will work in your farm pond can be challenging but researching thoroughly will insure that the pond will be effectively managed and healthy.