Sweetpotato tolerance to saflufenacil and rimsulfuron/thifensulfuron-methyl applied pretransplanting

Field studies were conducted at the Pontotoc Ridge–Flatwoods Branch Experiment Station in Pontotoc, MS, in 2016 and 2017 to determine sweetpotato crop response to saflufenacil and rimsulfuron/thifensulfuron-methyl. Saflufenacil treatments consisted of a factorial of two rates (25 or 50 g ai ha –1 ) by three application timings [0, 3, or 6 wk before transplanting (WBP)]. Rimsulfuron/thifensulfuron-methyl treatments consisted of a factorial of two rates (18/18 or 35/35 g ai ha –1 ) by two application timings (3 or 6 WBP). A nontreated check was included for comparison. Saflufenacil resulted in as much as 20% stunting injury in 2016, but ≤4% crop injury in 2017. Compared to the nontreated check, saflufenacil did not reduce yield of any sweetpotato grade regardless of application rate or timing. Findings from this trial indicate that saflufenacil applied in pre-transplanting burndown and field preparation procedures did not have a negative impact on the subsequent sweetpotato crop and that the current plant-back interval (4 to 5 mo) may be excessive. Applications of rimsulfuron/thifensulfuron-methyl at 35/35 g ha –1 made 3 WBP resulted in significant crop injury but did not reduce yield of any sweetpotato grade. Findings from this trial suggest that rimsulfuron/thifensulfuron-methyl applications up to 35/35 g ha –1 applied at least 6 WBP and 18/18 g ha –1 applied at least 3 WBP had little impact on sweetpotato crop growth and may be a safe preplant burndown option.