Fathen (Chenopodium album) a biotype resistant to dicamba

The broadleaf weed fathen (Chenopodium album) is a serious problem in maize crops In the 1979/80 season a biotype appeared that was resistant to the triazine herbicides and now this biotype is believed to occur in most maize fields Its control is principally by postemergence herbicides with dicamba being widely used Recently there have been reports of inadequate control of fathen by dicamba To test for resistance seeds were collected from fathen plants that were found alive in the field after application of dicamba These seed lines were grown in a glasshouse and treated with several rates of dicamba and other herbicides The fathen plants from one collection were not resistant to dicamba and were probably from plants that germinated after the field application of dicamba The fathen plants from the second collection all survived treatment with dicamba applied at 4 times the normal field rate These plants were killed by nicosulfuron and bromoxynil