Aquatic Weed Control

 When aquatic plants interfere with the intended use of a water resource, they are considered to be weeds.  Aquatic weed control is the development of a strategy or management plan that incorporates preventative methods, such proper pond construction and maintenance, biological methods such as grass carp and the use of labeled aquatic herbicides. At large weedy pond areas provide excess coverage for small fish and can result in overgrowing as well as oxygen depletion.

 The basic techniques used to control weeds in ponds are preventative, chemical, biological, and mechanical measures.

Preventative- Careful pond site selection and proper pond construction practices are the first steps in preventing aquatic weed problems.  For example, rooted aquatic weeds as well as algae begin growing in shallow water (less than 2 feet deep).  By deepening the edges of new and existing ponds you can minimize these shallow water areas.

Chemical- Chemical herbicides should be used as a temperature control method.  The majority weeds begin their growth in the early spring months when water temperatures are 55- 60 degrees F.  Spring months are the ideal time to apply herbicides.  Weeds tend to be smaller and easier to control at that time rather than during the hot summer months.  Aquatic herbicides used by Down South Pond and GrassRoots are nontoxic to fish when applied according to directions.

 Aquatic weeds that are killed by herbicides undergo decomposition in the pond.  This decomposition process consumes oxygen and can reduce the oxygen levels available to fish.   If the level drops below the necessary level for fish, fish kills due to oxygen depletion can occur.

 Treating ponds with herbicide in hot summer months is risky.  Oxygen levels tend to be lower during summer months and weed biomass levels tend to be higher.

Biological- Grass carp are a practical and economical way to control certain types of weeds in ponds and small lakes.  Grass carps control most submersed weed species such as naiads, coontail, and fanwort.  Only sterile grass carp may be used in Georgia ponds and lakes.

Mechanical- Various types of aquatic weed cutters and harvesters have been developed have been developed, but are not practical for most privately owned ponds.  Examining ponds frequently during the growing season and seine or rake weeds out of the water before seed formation occurs.