TECHNICAL AND ECONOMIC VIABILITY OF ADDING ACCASE AND ALS INHIBITORS TO GLYPHOSATE IN THE CONTROL OF WEEDS AND SOYBEAN GRAIN YIELD

Abstract

The continuous use of glyphosate in soybean has led to the appearance of resistant weeds. Thus, alternatives to manage resistant plants are needed, such as the use of products with different mechanisms of action. In this study, the efficacy of the post-emergence application of herbicides with different mechanisms of action in the control of weeds in soybean crop was tested. The experiment was conducted in the 2016/2017 season, in Cambé-PR, using randomized blocks, with four replications. We evaluated the following treatments: glyphosate; glyphosate + haloxyfop with chlorimuron-ethyl in sequential application; glyphosate + clethodim with chloransulam in sequential application; hand-hoe weeding; infested control. The exclusive use of glyphosate did not present efficient control of the weeds found. The species Digitaria insularis (sourgrass), Commelina virginica (Virginia dayflower) and Digitaria horizontalis (Jamaican crabgrass) were efficiently controlled by treatments glyphosate + haloxyfop with chlorimuron-ethyl in sequential application and glyphosate + clethodim with chloransulam in sequential application. However, the species Conyza bonariensis (hairy fleabane) and Ipomoea purpurea (common morning glory) were efficiently controlled only by hand-hoe weeding. The grain yield of soybean was higher in the treatments glyphosate + haloxyfop with chlorimuron-ethyl in sequential application and glyphosate + clethodim with chloransulam in sequential application, which yielded an average of 4,600 kg ha-1. Treatments glyphosate and infested control had a lower mass of 1000 grains and lower grain yield. The highest net revenue was obtained by treatments glyphosate + haloxyfop with chlorimuron-ethyl in sequential application and glyphosate + clethodim with chloransulam in sequential application. Therefore, the application of herbicides with different mechanisms of action (EPSP inhibitor, ACCase inhibitor and ALS inhibitor) improved weed control, soybean grain yield and profitability compared to the isolated application of glyphosate and the manual weeding.