Evaluation of Herbicides Applied to Soil for Control of Aquatic Weeds in Irrigation Canals

Abstract

Ninety-one herbicides and experimental compounds were evaluated for herbicidal activity on submersed aquatic weeds, Potamogeton pectinatus L. and P. nodosus Poir. Twenty-one of the compounds tested showed some phytotoxicity at 20 lb/A. The other compounds were completely inactive. 2,3,6-Trichlorophenylacetic acid (fenac) and 2,6-dichlorobenzonitrile (dichlobenil), showed outstanding activity with good persistence in water-saturated soil. Fenac and 2-(2,4,5-trichlorophenoxy)propionic acid (silvex), were tested in field trials in an irrigation canal in eastern Wyoming. The sodium salt and amide of fenac did not give adequate weed control at 5 lb/A. Spring applications of herbicides did not perform as well as fall ones. Mechanical incorporation of herbicides improved some results, but was of doubtful value.