Effect of Herbicide-Treated Irrigation Water on Four Vegetables

Abstract

Bodies of water that are treated with herbicides for aquatic weed control are often used as a source of irrigation water by landowners near the water body, but there is little information regarding the effects of experimental aquatic herbicides on common garden plants. Therefore, the goal of these experiments was to identify phytotoxicity of four herbicides on vegetables frequently cultivated by home gardeners. Sweet pepper, zucchini, tomato, and bush bean were irrigated with water containing bispyribac-sodium, quinclorac, topramezone, and trifloxysulfuron-sodium to identify the herbicide concentrations that damage these garden vegetables. Experiments were conducted during 2009 and repeated in 2010. Plants were irrigated four times during an 11-d period with the equivalent of 1.27 cm of treated water during each irrigation, then irrigated with well water until they were harvested 41 d after the first herbicide treatment. Values of the concentration of herbicide expected to reduce treated plants by 10% compared with control plants (EC10) were calculated from components of nonlinear regression. Analysis of visual quality and dry weight data revealed that bush bean was the most sensitive of the vegetable plants to bispyribac-sodium, trifloxysulfuron-sodium, and topramezone, whereas the species most sensitive to quinclorac was zucchini. Exposure of bush bean to 7.1, 0.9, and 1.2 parts per billion (ppb) of bispyribac-sodium, trifloxysulfuron-sodium, and topramezone, respectively, would be expected to cause 10% reductions compared with control plants, whereas exposure of zucchini to as little as 11.0 ppb of quinclorac would be expected to cause a 10% reduction in dry weight.