Selectivity of Herbicides Applied Isolated and in Combinations in Grain Sorghum

In Brazil, sorghum (Sorghum bicolor) has gained prominence as a second-crop option, serving as an alternative to maize, and is widely used both for straw production in no-until systems and for grain and forage for animal feed. However, weed management, particularly of grasses, within this crop is a significant challenge due to the limited availability of selective herbicides. Therefore, this study aimed to evaluate the selectivity of the herbicides trifluralin, atrazine, and mesotrione, applied individually or in combination during the postemergence phase of grain sorghum. Two field experiments were conducted to assess key variables including phytotoxicity, plant height, and grain yield. Applications of trifluralin and atrazine, either alone or in combination, resulted in mild to moderate phytotoxicity ranging from 5 to 16%, more pronounced at higher trifluralin rates, but did not negatively affect plant development or productivity. Similarly, the atrazine + mesotrione combination caused mild phytotoxicity symptoms, reaching 13%. In contrast, trifluralin + atrazine + mesotrione mixtures exhibited phytotoxicity levels ranging from 22 to 41% and led to significant productivity reductions across most evaluated dose combinations. These results highlight the importance of careful herbicide selection and appropriate application rates to achieve effective weed control without compromising the safety and productivity of sorghum crop.