The present paper had the objective to verify the efficiency of the herbicide pyrithiobac applied in post-emergence for cotton in order to control the species Cenchrus echinatus and Ipomoea grandifolia, in two different growth stage and in sequential way in fraction rates. The product pyrithiobac, in the rate of 0,5 l/ha plus Iharagen-S at 0,25% v/v, in post-emergence in one single rate, or two spraying in fraction rates (0,25 l/ha + 0,25 l/ha) was efficient to control both species, C. echinatus and I. grandifolia in the stage of 1 to 3 and 3 to 4 leaves, respectively. The fitotoxicity to the reagent cultivar IAC-20 was initially observed, but the symptom disappeared in the fifth day, without hazard injury to the crop.
Gossypium hirsutum; Cenchrus echinatus; Ipomoea grandifolia; pyrithiobac; post-emergence