Seletividade de atrazine + mesotrione aplicados em diferentes épocas na cultura da canola

Abstract

Weeds, especially wild radish and ryegrass, cause losses in productivity and the quality of harvested canola grains when not adequately controlled. Currently, there are few registered herbicides for controlling weeds infesting canola. In light of this, the objective of the study was to evaluate the selectivity of the commercial mixture composed of atrazine + mesotrione applied at different times and doses before canola sowing. The experiments were conducted in the field over two years (2022 and 2023) in a randomized block design, arranged in a 2 x 6 + 1 + 1 factorial scheme, with four repetitions. The treatments used in both experiments were: weeded control, doses of atrazine + mesotrione (250 + 25; 500 + 50; 750 + 75 g ha⁻¹) applied alone or in combination with clethodim (108 g ha⁻¹). Atrazine + mesotrione was applied at 10 and 5 days before sowing (DBS), and clethodim was applied in post-emergence when canola was at the 3 to 4 leaf stage. The herbicide atrazine + mesotrione, when applied at the highest dose, both alone and in combination with clethodim, caused high phytotoxicity to the canola hybrid Nuola 300. Atrazine + mesotrione applied at doses of 500 + 50 and 750 + 75 g ha⁻¹, 10 days before sowing (DBS), showed negative effects on the physiological variables of canola. The use of atrazine + mesotrione applied 5 days before canola sowing at a dose of 500 + 50 g ha⁻¹ and clethodim post-emergence on the Nuola 300 hybrid was the treatment that presented the best result for crop productivity. The mixture of atrazine + mesotrione, when applied at the lowest dose of 250 + 25 g ha⁻¹, alone or in combination with the herbicide clethodim, showed selectivity to the canola crop.