Aquatic weed control has in recent years developed into one of the most important phases of farm pond management in Georgia. Properly constructed ponds with adequate fertilization which were chemically treated four years ago show no reinfestation at this time. On the other hand, in experimental ponds which were not properly fertilized the results of chemical weed control were of extremely short duration. The more frequently used herbicides, Sodium arsenite, 2,4-D (ester and amines), 2,4-D-2,4,5-T combinations, and Copper sulphate are considered with regard to methods of application, cost of treatments, effectiveness on different plant species and duration of successful weed elimination. Sodium arsenite was found universally effective in the control of most submerged aquatic plant species. However, its toxicity to warm blooded animals and the caution necessary in its application and handling restrict its use to experienced technicians. Careless handling of this material in Georgia has resulted in injury to personnel as well as the loss of livestock in one instance. Growth regulating 2,4-D and 2,4,5-T compounds were effective in the control of most broad leafed emergent aquatics. The use of both oil and water carriers was evaluated. To achieve complete control, more than one application was usually required. Copper sulphate was found to be the most economical and effective algicide. Some of the newer aquatic herbicides, Dowpon, Pelletized 2,4-D, Kuron, Novon and Delrad are discussed in relation to their effectiveness. Particular emphasis was placed on the control of Manna grass (Glyceria sp.) with these chemicals. Those showing promise are further evaluated as to effectiveness on a large variety of plants. Dowpon appeared very promising in the control of aquatic grasses. Pelletized 2,4-D and Kuron, formulated for use on submerged aquatic species, gave excel1ent preliminary results. Cost of treatment per acre with these materials is somewhat higher than with sodium arsenite, however, certain advantages offered by these chemicals may offset increase in cost. Delrad was found to be effective in the control of most species of filamentous algae. The use of this material in Georgia was virtually prohibited because of rapid reinfestation following treatment, poor availability, and a high per acre cost of treatment. Aquatic herbicides were found to be an effective and economical means of eradicating most aquatic nuisances. The advantages and disadvantages of most materials are discussed and the newer herbicides are considered with regard to their use in future aquatic weed control work.
