Response of Bell Pepper and Broccoli to Simulated Drift Rates of 2,4-D and Dicamba

Field experiments were conducted at Wooster, OH, in 2010 and 2011 to evaluate the effect of simulated drift rates of 2,4-D, dicamba, and 2,4-D plus glyphosate on processing broccoli and bell pepper. Treatments were made in July of each year when bell pepper and broccoli were at the 10- and eight-leaf stage, respectively, and included five 2,4-D rates (1/50, 1/100, 1/150, 1/200, and 1/400 of the recommended field rate of 840 g ae ha(-1)), five dicamba rates (1/50, 1/100, 1/150, 1/200, and 1/ 400 of the recommended field rate of 560 g ae ha(-1)), and three rates of 2,4-D plus glyphosate (1/100, 1/200, and 1/400 of the recommended field rates). Crop injury was recorded at 7 and 28 d after treatment (DAT). Broccoli and bell pepper responded differently to simulated drift rates each year with higher initial injury ratings observed in 2010, and more persistent symptoms in 2011. 2,4-D at the 1/50 rate reduced broccoli yield by approximately 50% in 2010. Simulated drift rates of 2,4-D did not cause broccoli yield reduction in 2011, nor did simulated drift rates of dicamba, or 2,4-D plus glyphosate reduce yield either year. Although simulated drift treatments did not reduce total yield of bell pepper, the timing of fruit maturity was affected. Yield at first harvest was reduced by high simulated drift rates of each herbicide and by the herbicide tank mix. These results indicate that broccoli and bell pepper are sensitive to very low doses of 2,4-D and dicamba that are typical of those encountered in drift events. The impact of actual drift on delayed maturity and total yield of these crops is likely to be costly for the farmer.