Aquatic plants growing in ponds and lakes are beneficial for fish and wildlife. They provide food, dissolved oxygen and spawning and nesting habitat for fish and waterfowl. Aquatic plants can trap excessive nutrients and detoxify chemicals.
However, dense growths (over 25 percent of the surface area) of algae and other water plants can seriously interfere with pond recreation and threaten aquatic life.
Water plants can restrict swimming, boating, fishing and other water sports. Water plants can impart unpleasant taste, decaying vegetation emits offensive odors and algae can discolor pond waters.
Dense growths of plants can cause night time oxygen depletion and fish kills. Green plants produce oxygen in sunlight, but they consume oxygen at night.
Decomposing water weeds can deplete the oxygen supply, resulting in fish kills from suffocation. Dense plant growths can provide too much cover, preventing predation, and leading to stunted sportfish populations.
Prevention and Watershed Management: Prevention is the best way to reduce aquatic plant problems. It is cheaper and easier to prevent weed growth than to control weeds in your pond. Constructing ponds with steep slopes that drop quickly into deep water can prevent weeds from rooting.
Soil erosion and fertilizer runoff (including livestock wastes) are the two major causes of water weeds. Soil erosion magnifies the weed problems.
Eroded soil particles not only make the pond shallower and allow rooted weeds to quickly invade, but soil particles also transport fertilizer (absorbed nitrogen and phosphorus) that further stimulates weed growth.
Aquatic Plant Control Methods: Selection of the best treatment or combination of treatments depends on the species of water plant, the extent of the problem, economic considerations, local environmental conditions and pond uses.
First, be sure that you have an aquatic plant problem. Some aquatic plant growths are minor and temporary and do not require costly weed control actions, thereby saving you worry, time and money. If aquatic plants cover more than 25 percent of the pond surface area, you should consider implementing weed control.