Glyphosate no controle de Brachiaria brizantha em áreas cultivadas com Tifton 85 (Cynodon spp.)

• Autor(a) principal: Santos, Márcia Vitória
• Data de Publicação: 2006
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/4552
• topic: Pastagens; Tolerância; Herbicidas; Seletividade; Plantas daninhas; Brachiaria brizantha; Pastures; Tolerance; Herbicides; Selection; Weeds; Brachiaria brizantha; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOTECNIA

Brachiaria brizantha, a forage specie, is considered weed of difficult control when in pasture of Tifton 85 because, of its high capacity of interference and multiplication. Being important to search alternatives of controlling B. brizantha and the necessity to know real effects of glyphosate on Tifton 85 plants, three experiments were carried out in order to evaluate: glyphosate efficiency in controlling B. brizantha in plants cultivated in pots, submitted to herbicide before tillering, with four and five tillers and around 10 tillers at 0; 90; 180; 360; 720; 1.080; 1.440 and 1.800 g ha-1 , and in plants in established pasture at 0; 720; 1.440; 2.160; and 2.880 g ha-1; and tolerance of Tifton 85. B. brizantha control and Tifton 85 intoxication by glyphosate were based on visual percentage of plants with symptoms in relation to the control, varying from 0% to 100%. In the assays on pots, production and capacity of sprout of both forages were evaluated at 60 days after application (DAA) and 60 days after cutting (DAC), while in the assays of established pasture, it was evaluated at 300 DAA from dry matter. At 60 DAA, it was obtained a percentage of control superior to 90% from 133.60 g ha-1 when herbicide was applied before B. brizantha tillering and 365.63 g ha-1 with four to five tillers/plant. At assays with adult B. brizantha plants it was obtained control superior to 90% from 738.28 g ha-1 of glyphosate when cultivated in pots, and 1.721.25 g ha-1 when under field conditions. At those rates, intoxication levels of Tifton 85 plants were minimum, 1.21; 0.71; 12.05 and 4.13%, respectively. In the assays in pots, rates up to 720 g ha 1 provided dry matter reduction because of intoxication caused by herbicide, not killing plants when applied in plants with 10 tillers. Under field conditions, Tifton 85 plants treated with high herbicide rates (2.880 g ha 1 of glyphosate) showed low intoxication. Results showed higher tolerance of Tifton 85 to glyphosate, mainly in older plants, evidencing possibility of using this herbicide on B. brizantha control in areas cultivated with Tifton 85.