Sensitivity of kidney beans (Phaseolus vulgaris) to soil applications of S-metolachlor and imazethapyr

Tolerance of Montcalm and Redhawk kidney beans to preplant incorporated (PPI) and preemergence (PRE) applications of S-metolachlor, imazethapyr and their tank mix at the maximum label rate in soybeans (1×) and twice that rate (2×) was studied at two Ontario locations (Exeter and Ridgetown) in 2001 and 2002. There were no differences between the two cultivars in their responses to the herbicide treatments. Visual evaluations of crop injury never exceeded 2% for any herbicide treatment. With the exception of a 7% height reduction after the PPI application of imazethapyr plus S-metholachlor at the 2× rate, none of the other treatments reduced plant height, dry weight, seed moisture content or seed yield. At sites where there was a significant difference, the PRE application caused more crop injury than the PPI application. These results indicate that there is an acceptable margin of crop safety for PPI and PRE applications of S-metolachlor and imazethapyr alone and in tank mix combination in kidney beans in Ontario. Key words: Crop injury; crop tolerance; imazethapyr; S-metolachlor; yield.