Each year, Gerald Alexander receives numerous calls from landowners who have aquatic plant problems in their farm ponds that they can't control.
“Most aquatic plants are rarely a problem in ponds and don't require control,” said Alexander, Hempstead County staff chair with the University of Arkansas Cooperative Extension Service. “However, for people who don't want any vegetation in their ponds, any plant is a nuisance and must be removed.”
Alexander divides aquatic plants into four categories: algae, floating weeds, emersed (above-water) weeds, and submersed (underwater) weeds. Algae come in a variety of shapes and sizes, but they don't produce flowers or seeds like other aquatic plants, according to Alexander.
Microscopic algae, or planktonic algae, are small plants that are beneficial to ponds by providing food and oxygen for insects and fish through photosynthesis. Proper fertilization of farm ponds promotes the desirable growth of microscopic algae which are good for farm ponds and pond wildlife.
“However, excessive fertilization or organic pollution can lead to undesirable algal blooms that can be extremely harmful to pond health and wildlife,” Alexander warned. “These blooms can kill fish and cause health problems for humans. Ponds in extreme cases give off a sewer-like odor and fish from these ponds have an off-taste.”
Filamentous algae are probably the most common type of algae seen because they form floating mats, or pond moss, and frequently create problems.
They begin growth on the pond bottom in shallow water and then float to the surface.
Floating aquatic weeds float on or in the water and receive their nutrients from the water. Duckweed is an example of this type of aquatic weed. Because of the floating nature of these aquatic weeds, they can move with the wind and be found anywhere on the pond.
Emersed, or above water, weeds are rooted to the bottom in shallow water and may have parts of the plant extending at or above the water line, Alexander said. Waterlilies, sedges, cattails, grasses and several woody plants are examples of this type. Most plants in this category prefer the shoreline.
Submersed, or underwater, aquatic weeds grow under and up to the surface of the water. This family of aquatic plants is dependent upon water for support and they are not able to support themselves when removed from the water.
Control of submersed aquatic plants is more difficult because of their growth habits, the county agent said.
“Controlling aquatic weeds in a farm pond is best done by using a combination of methods,” Alexander said. These methods include grass carp, chemicals and mechanical equipment to drag aquatic plants out of the water. Each method has its advantages and disadvantages.
For assistance with farm pond weed control, contact your county Extension agent.
“The preferred farm pond will have a minimum 2-foot depth along the edges of the pond with enough algal bloom to prevent sunlight penetration below 16 inches,” Alexander said.