RESPOSTA DE BIÓTIPOS CAPIM - AMARGOSO (Digitaria insularis) DO SUDOESTE GOIANO AO HERBICIDA GLIFOSATO

Abstract

Glyphosate is one of the herbicide most used in agricultural crops in the world, its intensive use has contributed significantly to the selection of weed biotypes; Among the species resistant to glyphosate stands out the bittergrass. The objective of this work was to determine the chemical control of bittergrass (Digitaria insularis) biotypes in the southeast of Goiás by the herbicide glyphosate through the dose-response curve. The treatments were arranged in a 7 x 10 factorial scheme in a randomized complete block design, with four replications. Seven bittergrass biotypes (B1, B2, B3, B4, B5, B6 and B7) and ten doses of glyphosate from the Roundup Transorb® commercial formulation (480 g ha-1 ia) were evaluated. , 0.31, 0.21, 0.42, 0.84, 1.7, 3.3, 6.7, 13.4 and 26.8 kg ha-1 a.i.), respectively, representing the ratio : D, D / 16, D / 8, D / 4, D / 2, D, 2D, 4D and 8D, 16D where D is the manufacturer's recommended commercial product dose of 3.5 L ha- , 7 kg ha-1 ia) of the formulated product. The plants had four to eight tillers at the time of application. Bittergrass control was evaluated through phytotoxicity at 7, 14, 21, 28 and 56 days after application (DAA), dry biomass, number of tillers and height of the plants at 56 DAA and at 86 DAA of grass- The dry biomass and the number of tillers of the regrowth were evaluated. The biotypes of Silvânia 1 (B1), Gameleira 1 (B3) and Silvânia 2 (B5) showed evidence of resistance to herbicide glyphosate, due to the low levels of phytotoxification, as well as the biotypes from Silvânia 3 (B7), Orizona (B2) and Pires do Rio (B4) presented greater sensitivity to the herbicide Glyphosate, leading to a more efficient and fast control than the other evaluated biotypes. Subdose of less than 0.84 kg ha-1 a.i. provided restoration of all the biotypes being ineffective in the control of bittergrass plants.