ABSTRACT
Six field trials were conducted over a three-year period (2011, 2012, 2013) at the Huron Research Station, Exeter, Ontario and University of Guelph Ridgetown Campus, Ridgetown, Ontario to determine the effect of five postemergence (POST) application timings (1 - 2 trifoliate, 3 - 4 trifoliate, 5 - 6 trifoliate, 1st flower and 1st pod stage) of halosulfuron (35 and 70 g·ai·ha-1) on the tolerance of adzuki, black, white and kidney beans. All treatments including the non-treated control were maintained weed free during the growing season. Halosulfuron applied POST in black, white and kidney bean caused as much as 8%, 8%, 7%, 4% and 2% injury 1 WAA and 4%, 4%, 2%, 2% and 1% injury 2 WAA at 1 - 2 trifoliate, 3 - 4 trifoliate, 5 - 6 trifoliate, 1st flower and 1st pod stage application timings, respectively. The injury observed was transient with 1% or less injury 4 WAA and there was no adverse effect on the shoot dry weight, plant height, seed moisture content and yield of black, white and kidney bean. Injury was substantially higher in adzuki bean at all application timings. Halosulfuron applied POST caused as much as 66%, 47%, 50%, 39% and 36% injury 1 WAA; 77%, 68%, 64%, 51% and 42% 2 WAA; and 69%, 51%, 47%, 40% and 29% 4 WAA at 1 - 2 trifoliate, 3 - 4 trifoliate, 5 - 6 trifoliate, 1st flower and 1st pod stage application timings, respectively. Halosulfuron POST decreased shoot dry weight as much as 69%, 57%, 43%, 41% and 34%; plant height as much as 17%, 15%, 14%, 13% and 10%; and seed yield as much as 47%, 46%, 45%, 56% and 55% at 1 - 2 trifoliate, 3 - 4 trifoliate, 5 - 6 trifoliate, 1st flower and 1st pod stages, respectively. Based on these results, there is an adequate margin of crop safety for halosulfuron POST in black, white and kidney beans. However, there is not an adequate margin of crop safety for halosulfuron POST in adzuki bean at the application timings evaluated.