New technologies are being developed using mixtures of herbicides to manage a broader variety of weeds in multiple herbicide resistant crops such as soybean and cotton. As part of its regulation of pesticides, the US Environmental Protection Agency considers environmental risks, including impacts to nontarget plants potentially exposed to pesticide drift- including mixtures of herbicides. To provide information on possible effects of mixtures of herbicides on nontarget plants, we have conducted greenhouse and field studies using dicamba and glyphosate alone and in combination at rates of 0.01 to 0.2 x field application rates of approximately 830 and 563 g HA<sup>-1</sup> for glyphosate (as acid glyphosate) and dicamba, respectively. Growth and reproductive endpoints for a variety of native plants were evaluated. Our findings indicated that responses to combinations of glyphosate and dicamba resembled the responses to either of the herbicides with a few exceptions of an interactive response. Those species most sensitive to dicamba, e.g., broad-leaf plants, had mixture responses similar to dicamba alone; while species more sensitive to glyphosate, e.g. grasses, had mixture responses similar to glyphosate alone.

Effects of mixtures of dicamba and glyphosate on nontarget plants

254th National Meeting (2017)

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