Field trials were conducted in North Carolina in 2017 and Louisiana and Mississippi in 2018 to determine the effect of pretransplanting applications of diquat on sweetpotato crop tolerance, yield, and storage root quality. In North Carolina treatments consisted of two rates of diquat (560 or 1,120 g ai ha–¹) alone or mixed with 107 g ai ha–¹ flumioxazin and applied 1 d before transplanting (DBP), sequential applications of diquat (560 or 1,120 g ha–¹) 1 and 17 DBP, 107 g ha–¹ flumioxazin alone, and a nontreated check. In Louisiana and Mississippi treatments consisted of diquat (560 or 1,120 g ha–¹) applied 1 DBP either alone or followed by (fb) rehipping rows or 107 g ha–¹ flumioxazin immediately prior to transplanting. Additional treatments included 546 g ha–¹ paraquat applied 1 DBP and a nontreated check. In North Carolina injury was ≤3% for all treatments through 23 d after transplanting (DAP), and no injury was observed after 23 DAP. Visual sweetpotato stunting pooled across the Mississippi and Louisiana trials ranged from 1% to 14%, 0% to 6%, and 0% to 3% at 2, 4, and 6 wk after planting (WAP), respectively, and no crop injury was observed after 6 WAP. Diquat applied 1 DBP and not fb rehipping resulted in greater crop injury (12%) than comparable treatments that were rehipped (2%). In North Carolina single and sequential diquat applications resulted in reduced No. 1 sweetpotato yield (24,230 and 24,280 kg ha–¹, respectively) compared with the nontreated check, but No. 1 yield when diquat plus flumioxazin (26,330 kg ha–¹) was used was similar to that of the nontreated check. No. 1 yield did not differ by treatment in Louisiana and Mississippi.

Nomenclature: Diquat; sweetpotato; Ipomoea batatas (L.) Lam. ‘Beauregard', ‘Covington’, ‘Orleans'