Controlling weeds selectively is a challenge when producing grain sorghum [Sorghum bicolor (L.) Moench]. Pyroxasulfone, a preemergence (PRE) herbicide, has demonstrated excellent grass and broadleaf control in maize (Zea mays L.) and soybean [Glycine max (L.) Merr]. However, pyroxasulfone is not labeled for grain sorghum because crop injury is a major limitation. Our first objective was to evaluate five herbicide safeners in the greenhouse to determine their ability to protect sorghum from pyroxasulfone. Growth data indicated seed-applied fluxofenim provided the highest level of protection to emerging seedlings. A second objective was to evaluate fluxofenim for protecting sorghum from single and sequential pyroxasulfone applications in the field. A split-plot in a randomized complete block design evaluated six pyroxasulfone (whole plot) and two fluxofenim treatments (subplot) in 2015 and 2016. A single PRE treatment of S-metolachlor, an untreated-weedy control, and weed-free control were compared with pyroxasulfone to assess weed control, crop injury and stand count, and grain yield. Pyroxasulfone provided greater weed control than S-metolachlor. However, as pyroxasulfone rates increased both weed control and crop injury increased, regardless of safener. In contrast, sequential pyroxasulfone applications (90/120 or 120/90 g ai ha–1) did not elicit as much crop injury or stand reductions as a single PRE application at the same total rate (210 g ai ha–1) and maintained weed control, which resulted in higher yields. Despite increased crop tolerance and yield with sequential relative to single pyroxasulfone applications, these findings indicate a more effective herbicide safener for pyroxasulfone in grain sorghum is required.
ASJC Scopus subject areas
- Agronomy and Crop Science