Response of four market classes of dry bean to mesotrione soil residues

Field trials were established in 2001 and 2003 in Ontario to determine the potential of mesotrione applied pre-emergence (175 and 350 g a.i./ha) and post-emergence (100 and 200 g a.i./ha) to cause injury to cranberry, kidney, black, and white beans grown in rotation with maize, one and two years after application. Mesotrione applied pre-emergence at 175 and 350 g a.i./ha or post-emergence at 100 and 200 g a.i./ha to field maize in the previous year caused minimal visual injury (6% or less) and had no effect on shoot dry weight and yield of black and white beans except for black bean shoot dry weight and yield which were both reduced 12% with post-emergence mesotrione at 200 g a.i./ha. Mesotrione caused as much as 42% visual injury, 31% shoot dry weight reduction, and 42% yield reduction in cranberry and kidney beans. Post-emergence mesotrione caused more crop injury than pre-emergence mesotrione. Mesotrione applied pre-emergence or post-emergence at the labeled or twice the labeled doses in maize did not injure cranberry, kidney, black, and white beans two years after application. Based on these results, black and white beans can be safely grown in rotation with field maize treated with mesotrione pre-emergence or post-emergence at the labeled dose. However, a re-cropping interval of two years is recommended following application of mesotrione for cranberry and kidney beans.