Seletividade de herbicidas aplicados em isolado ou em mistura em tanque na cultura do trigo

Abstract

Wheat is one of the most important winter crops in Brazil, mostly cultivated in the states of the Southern Region. However, the application of herbicides used for weed control often causes injuries to the crop, impairing its development, growth, and consequently grain productivity. Therefore, the objective of this study was to evaluate the selectivity of herbicides applied either individually or in tank mixtures on the wheat cultivar ORS Absoluto. The experiments were conducted in a randomized complete block design with four replications in the years 2022 and 2023. The treatments included: 2,4-D choline (456 g ha-1), 2,4-D amine (700 g ha-1), dicamba (480 g ha-1), iodosulfuron (50 g ha-1), and clodinafop-propargyl (240 g ha-1), applied individually or in combinations, totaling 16 treatments, and a weeded control. The variables evaluated were wheat plant phytotoxicity at 7, 14, 21, 28, 35, and 42 days after treatment (DAT). Physiological characteristics (internal CO2 concentration, stomatal conductance, transpiration rate, photosynthetic rate, carboxylation efficiency, and water use efficiency) were evaluated at 28 DAT. At wheat harvest, spike number per area, spike length, number of filled and sterile grains, thousand grain weight, hectoliter weight, and grain yield were determined. The herbicide dicamba, applied alone or in combination with iodosulfuron, clodinafop-propargyl, 2,4-D choline, or 2,4-D amine, caused the highest levels of phytotoxicity to the wheat crop in all assessments. Clodinafop-propargyl, despite affecting physiological variables of the crop, was metabolized by the plants and the symptoms did not affect grain yield. The use of dicamba combined with iodosulfuron or clodinafop-propargyl caused the least damage to the crop compared to dicamba applied alone. Treatment with dicamba alone resulted in the lowest productivity. Clodinafop-propargyl applied alone demonstrated the best response for wheat grain yield components. Treatments clodinafop-propargyl, 2,4-D choline + clodinafop-propargyl, 2,4-D amine + clodinafop-propargyl, iodosulfuron + clodinafop-propargyl, 2,4-D choline + iodosulfuron + clodinafop-propargyl, and dicamba + iodosulfuron + clodinafop-propargyl were statistically equivalent as the most productive.