Efeito da Época de Aplicação de Herbicidas Sulfoniluréias no Controle de Azevém Anual na Cultura do Trigo

Abstract

The present study aimed to evaluate the group`s chemical herbicides sulfonylurea, alone and in combination, at different times of application in commercial wheat cultivars in infested area with annual ryegrass (Lolium multiflorum L.). The efficacy of the herbicide metsulfuron-methyl and iodosulfuron-methyl, alone and in combination in an area infested with ryegrass so to determine the level of control and phytotoxicity caused the cultivars in two application periods, as well as studying the effect of time of application of herbicides metsulfuron-methyl and iodosulfuron-methyl, alone and in combination, on the agronomic characteristics of wheat cultivars evaluated. The experiment was conducted in the experimental area of Unicentro - Campus CEDETEG, during the growing season of 2011, in Guarapuava, PR. The design was a randomized complete block with 16 treatments arranged in a factorial 4 x 2 x 2 compounds by applying metsulfuron-methyl (2.4 g i.a. ha?¹) and iodosulfuron-methyl (5.0 g i.a. ha?¹), alone and in combination and control (no application), using two commercial wheat cultivars (Quartzo and BRS Tangará) in two seasons of herbicide application at 21 DAS and 30 DAS. We evaluated the phytotoxicity cultivars used in the experiment, the treatments and associations of the isolated molecules, the level of control of annual ryegrass, using as reference the witness, as well as the effects of different treatments on the yield of agronomic traits of wheat (test weight - thousand seed weight and seed yield of wheat). Evaluations of phytotoxicity and control level were performed on days after application (DAA), thus: 3 DAA, 7 DAA, 10 DAA, 14 DAA, 17 DAA and 10 DAA, 17 DAA, 24 DAA and 31 DAA, respectively. Level data and control characteristics were subjected to analysis of variance and the means compared by Scott Knott. It can be concluded that there were differences in the level of control of annual ryegrass and phytotoxicity of wheat cultivars when compared to application time and sulfonylurea herbicide used, whether in use alone or in combination. To control the level of annual ryegrass was found that there was a difference when used sulfonylurea herbicides, and herbicide use in iodosulfuron-methyl alone and in combination with metsulfuron-methyl efficient in control. There herbicidal phytotoxicity when used iodosulfuron-methyl alone and in combination with metsulfuronmethyl herbicide on wheat cultivars Quartzo and BRS Tangará, as compared to the control. The time of application of herbicides iodosulfuron-methyl sulfonylurea, treatment isolated and metsulfuron-methyl + iodosulfuron-methyl treatment in combination, influenced the agronomic test weight, thousand seed weight and seed yield in wheat cultivars evaluated. In the second season of sulfonylurea herbicide application (30 DAS), obtained the highest grain yield of wheat, especially when used iodosulfuron-methyl herbicide treatment alone and metsulfuron-methyl + iodosulfuron-methyl, combination treatment.