Effects of post-emergence application of bentazon and fomesafen on eight market classes of dry beans (Phaseolus vulgaris L.)

Dry bean growers have a limited number of herbicide options available for weed management in Ontario. Four field trials were conducted in Ontario over a 2-year period (2003 and 2004) to evaluate the tolerance of black, brown, cranberry, kidney, otebo, pinto, white and yellow eye beans to the post-emergence application of bentazon plus fomesafen at 840+140 and 1680+280 g ai ha−1. Treatments included a non-treated check. All treatments were maintained weed free during the growing season. The eight market classes responded similarly to bentazon plus fomesafen. The post-emergence application of bentazon plus fomesafen caused minimal (less than 5%) and transitory visual injury at 14 and 28 days after treatment. Plant height was reduced by 13% in pinto beans and 9% in white beans. There was no effect on the plant height of the other market classes of dry beans evaluated. Bentazon plus fomesafen applied post-emergence did not have any effect on shoot dry weight, seed moisture content and yield. Based on these results, bentazon plus fomesafen at the proposed maximum use dose can be safely used for weed management in black, brown, cranberry, kidney, otebo, pinto, white and yellow eye bean production in Ontario. Additional research is needed to determine if cultivars within a market class of dry beans differ in their response to bentazon plus fomesafen.