Abstract
Field experiments were conducted in North Carolina between 2012 and 2014 to evaluate weed control and grain sorghum response to postemergence application of prepackaged pyrasulfotole and bromoxynil alone or mixed with protoporphyrinogen oxidase inhibitor or synthetic auxins herbicides. The experimental design was a randomized complete block with four replications. Regardless of application rate or mixing partners, application of pyrasulfotole plus bromoxynil on 25 to 45 cm tall sorghum controlled Palmer amaranth and sicklepod 90% or greater when applied on 2 to 10 cm and less than 5 cm tall seedlings, respectively. Complete control of morningglories was noted if pyrasulfotole plus bromoxynil rate was increased from 233 to 287 g active ingredient ha-1 or if growth regulating herbicides were included. Less than 10% crop injury within 7 days after treatment resulted from pyrasulfotole plus bromoxynil alone or combined with growth regulating herbicides, whereas addition of protoporphyrinogen oxidase inhibitor increased phytotoxicity to 30%. Compared to bromoxynil alone, grain yield was not reduced by postemergence application of pyrasulfotole plus bromoxynil alone. However, addition of mixing partners has been noted to cause significant yield reduction in some situations. These results suggest that prepackaged pyrasulfotole plus bromoxynil alone or combined with other herbicides can be an important tool to manage troublesome weeds in grain sorghum in the Southeastern region of the United States.