Tolerância de gergelim (Sesamum indicum), carinata (Brassica carinata) e mostarda-indiana (Brassica juncea) a herbicidas aplicados em pré e pós-emergência

Abstract

The diversification of feedstocks for food, industrial, and biofuel purposes has increased interest in oilseed crops such as carinata, Indian mustard, and sesame, for which information on herbicide tolerance remains scarce. Therefore, this study aimed to evaluate the tolerance of these three species to herbicides applied pre- and post-emergence, as well as the influence of soil conditions and herbicide rates on crop response. The dissertation comprised three articles, one for each species. The experiments were conducted under greenhouse conditions, with four replications. In the pre-emergence experiments, a randomized complete block design (RCBD) was used in a 2 × 5 factorial arrangement (two soil conditions × five herbicide rates), with clomazone, quinclorac, and fluroxypyr-methyl evaluated individually under two soil conditions. In post-emergence, a completely randomized design (CRD) with five herbicide rates was used to individually evaluate dicamba, quinclorac, halauxifen-methyl, florpyrauxifen-benzyl, and fluroxypyr-methyl. Tolerance was assessed based on visual crop injury, plant height, shoot dry mass, effective doses required to reduce the evaluated variables by 10% and 20%, and the Mean Tolerance Index (MTI). The experiments were repeated in two experimental periods. In carinata, quinclorac showed response associated with the highest effective doses estimated to cause a 10% reduction in crop response, with 43.00 g a.i. ha⁻¹ in pre-emergence, regardless of soil condition, and 59.83 g a.i. ha⁻¹ in post-emergence. In Indian mustard, quinclorac had an ED₁₀ of 32.96 g a.i. ha⁻¹ in pre-emergence, regardless of soil condition, whereas in post-emergence, no sufficient growth reduction was observed to estimate the ED₁₀ by the MTI for halauxifen-methyl. In sesame, fluroxypyr-methyl had an ED₁₀ of 18.79 g a.e. ha⁻¹ in pre-emergence and 22.70 g a.e. ha⁻¹ in post-emergence. The response to fluroxypyr-methyl differed among species and between application methods, whereas quinclorac showed distinct responses between sesame and the brassica species evaluated. Overall, the results demonstrate that tolerance of these oilseed crops depends on the active ingredient, herbicide rate, and application method. The tolerance of the same species to the same herbicide may vary according to the application method, whether pre- or post-emergence. A shared mechanism of action among herbicides is not sufficient to predict crop tolerance. These results provide a basis for prioritizing active ingredients for field validation and for developing safer chemical weed management strategies for these crops.