Soybean Tolerance and Early-Season Weed Control from Preemergence Treatments Using Metribuzin and Pyroxasulfone.

A field experiment was conducted in 2021 to evaluate the preemergence activity of metribuzin (group 5) and pyroxasulfone (group 15) herbicide combinations in the control of several weed species and to determine their effectiveness as preemergence options in soybean [Glycine max (L.) Merr.] weed management systems. All treatments provided nearly ideal control of Palmer amaranth [Amaranthus palmeri (S.) Wats.] (99%), pitted morningglory [Ipomoea lacunosa (L.)] (better than 95%), and prickly sida [Sida spinosa (L.)] (better than 97%) by 35 days after preemergence application (DA PRE). No significant impact of preemergence treatments was observed on stand loss. Overall, preemergence treatments resulted in less than 6% chlorosis and necrosis by 35 DA PRE. Additionally, only treatments with Glory® at 1.25 lb/ac (metribuzin) or 5.75 fl oz/ac of Zidua® (pyroxasulfone) plus Glory at 1.25 lb/ac resulted in 7% and 5% of crop stunting, respectively, by 35 DA PRE. In contrast, other treatments resulted in less than 1% visible stunting. Therefore, all herbicide treatments tested resulted in desirable weed control and minimal impact on early crop development. Utilizing a combination of herbicide sites of action could minimize the expansion of herbicide resistance. Generally, preemergence treatments do not provide robust weed control persisting for the entire critical weed-free period of soybean (from emergence to V4). Therefore, timely postemergence applications should be recommended to reduce possible yield impacts. [ABSTRACT FROM AUTHOR]