Content area
Full text
Halosulfuron-methyl, a sulfonylurea herbicide, was registered for broadleaf weed control in dry bean. This herbicide has an adequate margin of crop safety in white bean, but causes unacceptable injury to adzuki bean. Halosulfuron-methyl absorption, translocation, and metabolism were evaluated in white and adzuki bean using radiolabeled herbicide to determine if differences in these parameters could explain the difference in crop safety between these two species. Adzuki bean had more rapid halosulfuron-methyl absorption than white bean. Adzuki bean reached 90% absorption (t^sub 90^) 26.2 h after treatment (HAT), whereas white bean required 40.1 HAT to reach t^sub 90^. The maximum halosulfuron-methyl absorption was higher in adzuki bean (75.7%) than in white bean (65.3%). More ^sup 14^C-halosulfuron was translocated to the apex, first trifoliate, stem above the treated leaf, and roots in aduzki bean than in white bean. The maximum radioactivity translocated out of treated leaf was higher in adzuki bean (17.7%) than in white bean (12.1%). Halosulfuron-methyl was broken down to the same metabolites in white and adzuki bean. The half-life of halosulfuron-methyl in adzuki bean was 16 HAT, compared with less than 6 HAT in white bean. More herbicide remained as the free acid in adzuki bean compared with white bean over the entire 48-h time course. The differential tolerance of white and adzuki bean to halosulfuron can be attributed to greater absorption and translocation and decreased metabolism in adzuki bean.
Nomenclature: Halosulfuron; white bean, Phaseolus vulgaris L.; adzuki bean, Vigna angularis (Willd.) Ohwi & H.Ohashi.
Key words: Halosulfuron-methyl, sulfonylurea.
(ProQuest: ... denotes formulae omitted.)
White and adzuki bean are two different dry bean species. More than 23 million t of dry bean were produced worldwide on a 29-million-ha harvested area in 2013 (FAOSTAT 2014). Weed interference can result in substantial yield losses in dry bean (Blackshaw and Esau 1991; Chikoye et al. 1995, 1996; Wilson et al. 1980) and herbicides are one of the most common weed management strategies used in dry bean production. When this study was initiated, imazethapyr was the only soil-applied drybean herbicide for broadleaf weed control in Ontario. Although imazethapyr is very effective for broadleaf weed control in dry bean, one concern is its narrow margin of crop safety under some environmental conditions (Arnold et al. 1993; Bauer et...