Seletividade e eficácia de herbicidas aplicados em isolado ou associados na cultura do feijoeiro e das plantas daninhas

Abstract

Losses in bean grain yield due to weed competition, particularly with Urochloa plantaginea (alexandergrass), can reach up to 80% if no control method is adopted. This study aimed to evaluate the selectivity and efficacy of herbicides applied alone or in combination in bean and weed crops. The experimental design was a randomized block with four replications. The following herbicides were used for pre-emergence of the bean: fomesafen+s-metolachlor (298.85+1294.56 g ha-1 ), piroxasulfone+flumioxazin (120+80 g ha-1 ). For post-emergence, the following herbicides were used: bentazon+imazamox (600+28 g ha-1 ), fomesafen+smetolachlor (298.85+1294.56 g ha-1 ), fluazifop+fomesafen (225+225 g ha-1 ), fomesafen (250 g ha-1 ), fluazifop-p-buthyl (250 g ha-1 ), plus two witnesses, one weeded and one infested. The phytotoxicity of the bean cultivar SCS 204 Predileto and the control of alexandergrass at 07, 14, 21, 28, 35, and 42 days after the application of the treatments (DAT) were evaluated. The gas exchange variables were measured at 60 DAT. At pre-harvest of the bean, the number of pods per plant, the number of grains per plant, the weight of one thousand grains, and grain yield were determined. The best control of alexandergrass, above 80%, was obtained with the isolated application of fluazifop-p-buthyl and the mixtures of fomesafen+smetolachlor+fluazifop-p-buthyl. The application of piroxasulfone+flumioxazin+bentazon+imazamox caused the highest phytotoxicity in common beans. The use of fomesafen alone and the association of s-metolachlor + fluazifop-p-buthyl caused the highest grain yield.