MISTURAS DE HERBICIDAS: EFEITOS DE ADJUVANTES NO CONTROLE DE PLANTAS INFESTANTES NA CULTURA DA SOJA

Estudaram-se efeitos de misturas de graminicidas com latifolicidas, aplicados em pós-emergência, acrescidos ou não de seus respectivos adjuvantes, no controle de plantas infestantes na cultura da soja (Glycine max (L.) Merrill) cv. IAC-8, em condições de campo. Os tratamentos consistiram em quatro graminicidas (haloxifop-metil, HM; sethoxydim, S; quizalofop-etil, QE e fluazifop-p-butil, FpB) e quatro latifolicidas (chlorimuron-etil, CE; fomesafen, Fom; fluoroglycofen, Flu e lactofen, Lac), aplicados isoladamente e em misturas, além das testemunhas com e sem convivência da cultura com a comunidade infestante. Os resultados mostraram que os adjuvantes, de maneira geral, intensificaram a injúria dos herbicidas. Os graminicidas mais eficazes, aplicados isoladamente ou em misturas, no controle de Eleusine indica e de monocotiledôneas, foram HM, QE e FpB. Não houve diferenças significativas no controle de Digitaria horizontalis entre os quatro graminicidas isolados; porém, as melhores misturas foram as que utilizaram os graminicidas QE ou HM. Para controle de Mollugo verticillata, os melhores tratamentos foram obtidos com Lac aplicado isoladamente e com as misturas de QE, S ou HM com Fom e seus respectivos adjuvantes. As misturas de tanque apresentaram efeitos predominantemente antagonísticos no controle de E. indica, D. horizontalis e monocotiledôneas. Efeitos estatis-ticamente antagonísticos e sinergísticos no controle de M. verticillata foram obtidos, respec-tivamente, nas misturas de tanque com Lac e com Fom. Uma possível interação entre os adjuvantes e as misturas de herbicidas ocorreu nas avaliações de controle para E. indica, quando as misturas de S ou de HM foram usadas com ou sem adjuvantes. Os tratamentos com herbicidas não influíram na produção do cultivar de soja IAC-8.Mixtures of narrowleaf and broadleaf herbicides, with or without their respective surfactants, were evaluated as to postemergence selectivity for weed control in a soybean (Glycine max (L.) Merrill) cv. IAC-8 field experiment. Four narrowleaf herbicides (haloxyfop-methyl, HM; sethoxydim, S; quizalofop-ethyl, QE and fluazyfop-p-butyl, FpB) and four broadleaf herbicides (chlorimuron-ethyl, CE; fomesafen, Fom; fluoroglycofen, Flu and lactofen, Lac) were applied either alone or mixed. Two controls, manual weeding and no weeding, were included. The surfactants increased the fitotoxicity of the herbicides. The most effective narrowleaf herbicides applied either alone or in mixtures, in controlling Eleusine indica and narrowleaf weeds were HM, QE and FpB. No significant differences were observed among the four narrowleaf herbicides for the control of Digitaria horizontalis Willd. However, the best mixture combinations were those with QE or HM. The best control of Mollugo verticillata L. was obtained with Lac and mixtures of Fom and QE, S and HM with their respective surfactants. The tank mixtures resulted in antagonistic effects for the control of E. indica, D. horizontalis and narrowleaf weeds. Antagonistic effects were observed in the control of M. verticillata, when Lac was mixed with the following herbicides: S, HM, QE or FpB. Sinergistic effects were observed in the control of this species with mixture of Fom with S, HM and FpB. A possible interaction among the mixtures of herbicides with their surfactants was observed in E. indica control, when the mixtures with narrowleaf herbicides, S or HM, were used, alone or mixed with their respective surfactants. Soybean production was not affected by the tested herbicides treatments, when compared with the manual weeded control