Field Evaluation of Low-Dose Metering and Polymer Endothall Applications and Comparison of Fluridone Degradation from Liquid and Slow-Release Pellet Applications

摘要

Field studies were conducted to evaluate three herbicide delivery system techniques. Metering pumps were used to apply low rates of endothall (0.4 mg/L) over a 72- to 96-hr period for control of sago pondweed in western irrigation canals. Treatments were evaluated for efficacy and feasibility to use under a variety of flow conditions. Treatments effectively controlled sago pondweed, and the development of a prototype metering pump greatly improved the feasibility of conducting treatments in remote settings where flow rates often vary greatly within a 24-hr period. In addition to metering technology, a new granular supersorbent polymer formulation of endothall that contains 61 percent active ingredient was evaluated in Lake Weohyapapka, Florida. These evaluations were conducted to compare efficacy and applicator handling properties versus the conventional clay formulation (10.1-percent active ingredient). The new formulation required 85 percent less bulk material than the conventional clay and presented no problems with dust creation. Although no differences in efficacy on hydrilla were noted between the products, reduced applicator exposure through decreased product handling and the time required for herbicide application were all seen as significant benefits of the new formulation. Lastly, the slow-release pellet (SRP) of the herbicide fluridone was applied to research ponds near Gainesville, FL, to improve the understanding of the release properties of this product. Following application of rates calculated to achieve 150 micrograms/L, the liquid aqueous suspension (AS) and SRP showed distinct differences in residues and dissipation. Initial concentrations following SRP application were reduced fivefold compared with the AS, whereas, the half-life of the SRP was estimated to be fivefold greater than that of the AS.