Difenzoquat for Wild Oat(Avena fatua)Control

Abstract

Postemergence difenzoquat (1,2-dimethyl-3,5-diphenyl-1H-pyrazolium) for wild oat(Avena fatuaL.) control in spring wheat(Triticum aestivumL.), durum wheat(Triticum durumDesf.), and barley(Hordeum vulgareL.) was evaluated in the field, greenhouse, and controlled environmental chamber. Wild oat control with difenzoquat was greater at the five- that at the three and one-half or two-leaf stages of growth. Barley tolerance to difenzoquat was excellent; however, spring wheat tolerance was influenced by cultivar. Durum wheat generally was more tolerant of difenzoquat than spring wheat. Tank mix combinations of broadleaf herbicides with difenzoquat had no effect on crop injury or wild oat control. Wild oat control with difenzoquat was greatest with adequate soil moisture, adequate fertility, warm air temperatures and high relative humidity. A simulated rainfall of 0.25 mm within ½ h or 1 mm within 4 h of application reduced wild oat control with difenzoquat.

Influence of environmental factors on glyphosate efficacy when applied to Avena fatua or Urochloa panicoides

“…For A. fatua no signi®cant dierences in glyphosate ecacy could be observed between the two relative humidity conditions used. This observation is different from that reported earlier for A. fatua treated with difenzoquat (Miller et al, 1978) and asulam (Sharma et al, 1978). For U. panicoides the reasons for the better control under the Fig.…”

“…Glyphosate ecacy was reduced under most conditions of lower soil moisture content ( Figs 1±5). This observation is similar to that reported for A. fatua using other herbicides (Jecoat et al, 1977;Miller et al, 1978;Dortenzio & Norris, 1980) and U. panicoides using glyphosate (Felton et al, 1990) but is the ®rst report of this eect using glyphosate on A. fatua. In addition, this response is identical to that seen for glyphosate in other species (Moosavi-Nia & Dore, 1979;Ismael et al, 1983).…”

Effect of Soil Moisture on the Efficacy of Foliar-Applied Wild Oat Herbicides

“…In contrast, moisture supply had no effect on the control of wild oat treated with flamprop methyl. The differences between the results reported here and those reported by Miller et al (1978Miller et al ( , 1979 probably relate to differences in experimental conditions. The fact that in the previous studies SWC was not expressed as soil water potential, i.e., as -MPa, precludes direct comparisons of the results.…”

“…Controlled environment studies have subsequently demonstrated significant reductions in the activity of flamprop methyl (Jeffcoat et al 1977), difenzoquat (Miller et al 1978) Dortenzio and Norris (1980) and Akey and Morrison (1983) comparable reductions in activity of diclofop methyl applied to wild oat were observed. In contrast, the 6% reduction in difenzoquat activity at low SWC was much less, and the 8% reduction in flamprop methyl activity considerably greater, than reported by Miller et al (1918Miller et al ( , 1979.In Miller's experiments wild oat control with difenzoquat was reduced from 60% under high-moisture conditions to less than 25% when the plants were severely stressed.…”

A possible involvement of gibberellin in the mechanism of Avenafatua resistance to triallate and cross‐resistance to difenzoquat

“…Surprisingly, however, triallate-resistant populations were cross-resistant to the unrelated bipyridilium herbicide, difenzoquat (O'Donovan et al, 1994;Rashid et al, 1997a). As well as being structurally dierent from triallate and EPTC, difenzoquat is applied after emergence at the 3±5 leaf stage of A. fatua (Miller et al, 1978). In Alberta, difenzoquat was not used in ®elds before A. fatua resistance was detected but, in a few cases, had been applied to control A. fatua infestations that were poorly controlled with triallate.…”