SELETIVIDADE DE HERBICIDAS EM PÓS-EMERGÊNCIA NA CULTURA DO GIRASSOL

Abstract

Concomitant with the expansion of the culture, there has been a growing difficulty in managing weeds present in sunflower, mainly due to the limited options of selective herbicides. The objective was to evaluate the selectivity of post-emergence herbicides in sunflower culture, in order to provide support for the chemical control of weeds in the crop. For this, two experiments were conducted in a greenhouse, using a randomized block design. In experiment 1, the treatments consisted of sunflower hybrids (Helio 250, Helio 251, Helio 260 and Tera 204 CL) and herbicides sulfentrazone, tembotrione, mesotrione, atrazine and flumetsulam+s-metolachlor, in addition to a control without application. In experiment 2, the treatments consisted of two herbicides, tembotrione (84 g ha-1 i.a.) and flumetsulam+s-metolachlor (96 + 960 g ha-1 i.a.), evaluated at seven doses corresponding to 0%; 25%; 50%; 75%; 100%; 125% and 150% of the recommended doses. The percentage of phytotoxicity and dry shoot mass of the plants were evaluated. It was found that the herbicide sulfentrazone caused less phytotoxicity to all hybrids, being a viable alternative for post-emergence weed management in sunflower culture. For the sunflower hybrid Tera 204 CL, the dose of 21 g ha-1 i.a. of tembotrione was the most selective, with a dose of 42 g ha-1 i.a. of tembotrione showing moderate tolerance. Flumetsulam+s-metolachlor applied at a dose of 24 + 240 g ha-1 i.a. did not cause injury to sunflower culture.