Ponds have a variety of uses. Some provide aesthetic value, while others are used for weekend fishing or as commercial fisheries. Others provide storm runoff control. Whatever the purpose, they are all subject to problems from weeds. The use of weed killer compared with other methods provides advantages and disadvantages for the pond owner.
Types of Vegetation
There are several categories of plants and weeds that can become a nuisance in a pond. Emergent vegetation is that which rises above the surface of the water--like cattails, bulrushes, spike-rushes, smartweeds and arrowhead. Submerged vegetation remains beneath the surface. Common varieties include pondweeds, naiads, Eurasian watermilfoil, elodea and coontail. Floating vegetation floats on the surface and includes water lily, water lotus, watermeal and duckweeds.
Types of Control
Mechanical control of weeds is only practical when dealing with small ponds and small amounts of weeds. Biological controls involve identifying the types of weeds to be eradicated and finding the natural predator that will do the job safely. Chemical controls involve the use of herbicides to remove unwanted vegetation. Herbicides often come with risks.
Benefits of Weed Killer
According to the University of Florida, the advantages in using chemical weed killers include controlling perennials, which do not respond well to other weed-control methods. Using chemical controls allows you to single out specific types of vegetation and avoid damage to desirable vegetation. Use of pre-emergent weed killers can stop weeds from becoming a problem.
Some herbicides may be toxic to fish, other water life and humans. Using too much weed killer at a time or on a cloudy day can dramatically impact oxygen levels in the pond, resulting in possible fish kill. Chemical control is more expensive than other types of control. It can create taste and odor problems and can limit use of the water after treatment.
Chemical Weed Killers
Check with local extension offices or game and fish agencies for approved weed-control chemicals in your area. Effective chemicals (depending upon the vegetation being treated) include chelated copper compounds, Fluridone, Glyphosate, Diquat and Endothall. Some may not be allowed in water used for livestock or to irrigate food crops, so check labels and restrictions carefully.