Seletividade de herbicidas aplicados em diferentes horários na cultura do trigo

Abstract

The application of herbicides in agricultural crops at different times still raises questions regarding selectivity, and wheat is no exception. Therefore, the aim of this study was to evaluate the effect of herbicides on the morphophysiology of the TBIO Toruk wheat cultivar when applied post-emergence at different times. The experiment was set up in randomized blocks arranged in a 4 x 7 factorial scheme with four replications. Factor A included application times (9, 12, 15, and 18 h), and Factor B included treatments (clodinafop-propargyl – 48 g ha-1, iodosulfuron-methyl – 3,5 g ha-1, pyroxsulam – 18 g ha-1, bentazon – 720 g ha-1, 2,4-D amina– 806 g ha-1 e metsulfuron-methyl – 3,6 g ha-1), plus a control without any product. The evaluated variables included phytotoxicity caused by the herbicides to wheat, height, stem diameter, leaf area, physiological characteristics (chlorophyll index, internal carbon concentration, photosynthetic rate, stomatal conductance, transpiration rate, water use efficiency, and carboxylation efficiency), and the dry mass of wheat aerial parts. The results demonstrate that the percentage of phytotoxicity was not elevated when all herbicides were applied to the TBIO Toruk wheat cultivar. Among the evaluated herbicides, pyroxsulam showed the highest phytotoxicity in all assessments and application times, while iodosulfuron-methyl had the lowest phytotoxic effects. The application of herbicides at 12 and 3 p.m. resulted in the highest phytotoxicity and negative effects on wheat physiological characteristics. Pyroxsulam applied at 3 p.m. caused a reduction in wheat plant dry mass. Bentazon, 2,4-D amine, and iodosulfuron-methyl showed the best results for most of the evaluated variables.