Seletividade de herbicidas e controle de plantas daninhas no sistema de produção da canola

Abstract

Canola, an important global oilseed, has been facing challenges in Brazil due to the scarcity of herbicides and the prohibition of transgenics in the country, impacting weed management. Based on this, the generation of knowledge and the development of innovative technologies to guide management would directly contribute to the expansion of this crop, boosting crop diversification and income generation. In this context, the objective of this work was to evaluate the potential selectivity of herbicides applied in canola cultivation, as well as their effectiveness in weed control in the crop. This study was conducted in the form of an article. Field experiments were carried out in the agricultural year 2022/23, at different locations in the state of Minas Gerais (Lavras and Ijaci), using a randomized block design with split plots (4 × 4) + 1, with four replications. The levels of factor one were the pre-emergence treatments: clomazone, s-metolachlor, clomazone + s-metolachlor, without pre-emergence herbicide; and factor two were the post-emergence treatments: quinclorac, dicamba, quinclorac + dicamba, without post-emergence herbicide; plus an additional treatment composed of the control (hand weeding). The evaluated components were: number of weeds (m-2), phytotoxicity to canola plants, initial and final plant stand, SPAD index, final height (cm-1), number of branches and pods per plant, number of seeds per pod, yield (kg ha-1), and oil and protein content (%) of

canola seeds. A significant interaction (p <0.05) was observed between pre and post- emergence treatments only for phytotoxicity to plants and SPAD index, at 7 and 28 days,

respectively, after application of post-emergence herbicides in Lavras-MG. The other evaluated components showed significant differences between treatments, either in pre or post-emergence, or both, except for initial and final plant stand, number of branches and pods per plant in both locations (Lavras-MG and Ijaci-MG) and number of seeds per pod for

Lavras-MG, which did not show significant differences. The herbicides clomazone in pre- emergence and quinclorac and dicamba in post-emergence are not registered for use in canola

in Brazil; however, although they caused phytotoxicity to plants, they did not generate harmful effects on the analyzed components. Additionally, they promoted significant contributions to weed reduction in the area, without affecting the productivity and quality of canola grains, along with s-metolachlor, already registered for use in pre-emergence. It is concluded that the evaluated herbicides demonstrated potential selectivity and effectiveness in weed control in canola cultivation, laying the groundwork for further research aiming to include them in the crop production system.