TOLERÂNCIA DE HÍBRIDOS DE GIRASSOL AO HERBICIDA PIROXASULFONA + FLUMIOXAZINA

Abstract

Sunflower (Helianthus annuus L.) is a crop of great economic and environmental importance, especially in Brazil, where it is cultivated as an alternative for the second harvest. Its production has been growing in the country, especially in the state of Goiás. However, the presence of weeds is a significant problem for the crop, impairing crop productivity. The objective of this study was to evaluate the tolerance of four sunflower hybrids to the application of the herbicide mixture pyroxasulfone + flumioxazine. The experiment was conducted in the field at the Instituto Federal Goiano, in Urutaí-GO, using a randomized block design in a 4 x 2 factorial scheme, corresponding to the four sunflower hybrids (Helio 250, Helio 251 Helio 260 and Tera 204 CL), subjected to two doses of pyroxasulfone + flumioxazine (Kyojin®): 0 and 150 ml bw ha-1. The herbicide was applied at the V8 stage. Phytotoxicity was evaluated at 7, 14, 21 and 28 days after application (DAA). At 28 DAA, shoot dry mass and plant height were evaluated. The Helio 260 hybrid showed lower phytotoxicity and higher plant dry mass and height, regardless of the herbicide application, indicating its greater tolerance to the pyroxasulfone + flumioxazine mixture. The Tera 204CL hybrid was the most affected by the treatment, presenting lower averages in all variables analyzed. The herbicide application reduces shoot dry matter and plant height. It is concluded that the Helio 260 hybrid is the most promising for cultivation in systems that require chemical weed control, offering better results in terms of herbicide tolerance. These findings can guide producers in choosing more tolerant hybrids, optimizing weed management without compromising sunflower productivity.