Wild-oat herbicide studies: barban herbicidal activity for wild-oat ( Avena fatua L.) control as influenced by adjuvants

Abstract

The effect of barban at 0·35 kg a.i./ha alone or in mixture with eight surfactants at 0·5% (v/v), and two organic salts at 0·5% (v/w) on wild oat ( Avena fatua L.) fresh weight was investigated in the glasshouse. Barban with Atplus 411F and with Renex-36 reduced wild-oat fresh weight by 68–77% and 69–86%, respectively, compared with the untreated control, whereas barban alone reduced fresh weight by 36–48%. Barban with added ammonium sulphate also reduced fresh weight by 71%. The three-way mixture (barban+surfactant+ammonium sulphate) did not further reduce fresh weight. Mixtures of Atplus 411F and Renex-36 added in different proportions to barban reduced fresh weight by amounts similar to individual combinations of each surfactant and barban. The increased activity of barban when applied with Renex-36 counteracted the antagonistic effect of 2,4-D isopropyl ester or MCPA iso-octyl ester on wild-oat fresh-weight reduction, compared with barban plus 2,4-D or MCPA without surfactant. Simulated rainfall did not decrease wild-oat fresh-weight reduction with the barban/Renex-36 mixture. Under field conditions, barban plus Atplus 411F and ammonium sulphate gave better wild-oat control than barban alone and increased wheat-grain yield. This treatment also did not reduce wheat tolerance. More [ 14C]-barban was absorbed by wild oat when [ 14C]-barban was mixed with Atplus 411F or Renex-36 than when applied alone. The increased adsorption may provide some explanations for the improved wild-oat control with barban/adjuvant mixture.