Response of dry bean to preplant incorporated and preemergence applications of pyroxasulfone

Three field trials were conducted over a 2-yr period at Exeter (2007, 2008) and Ridgetown (2007), Ontario to evaluate the tolerance of two market classes and two cultivars of each market class (cranberry, Etna and Hooter; kidney, Red Kanner and Red Hawk) of dry bean to preplant incorporated (PPI) and preemergence (PRE) applications of pyroxasulfone at 209 and 418 g a.i. ha -1 . All treatments including the non-treated control were maintained weed free during the growing season. There was greater injury when pyroxasulfone was applied PPI than PRE, and injury was greater with the high rate at 1, 2, and 4 wk after emergence (WAE). Pyroxasulfone at 209 and 418 g a.i. ha -1 caused as much as 32 and 61% visible injury when applied PPI and 15 and 30% visible injury when applied PRE in dry bean, respectively. Pyroxasulfone at 209 and 418 g a.i. ha -1 decreased shoot dry weight as much as 60 and 80% when applied PPI and 30 and 50% when applied PRE in dry bean, respectively. Plant height was not affected by pyroxasulfone application timing, but was rate dependent. Height was reduced 14, 13, 22 and 13% at 209 g a.i. ha -1 and 24, 31, 42 and 27% at 418 g a.i. ha -1 for Etna, Hooter, Red Kanner and Red Hawk cultivars, respectively. Dry bean yield was reduced as much as 29% at 209 g a.i. ha -1 and 45% at 418 g a.i. ha -1 . This research shows that there is not an adequate margin of crop safety for pyroxasulfone applied PPI or PRE at the rates evaluated in Etna, Hooter, Red Kanner and Red Hawk dry beans in Ontario.Key words: Cranberry bean, Etna bean, kidney bean, Hooter bean, Phaseolus vulgaris L., Red Hawk bean, Red Kanner bean, pyroxasulfone