Response of wild oat (Avena fatua) to residual and non-residual herbicides in canola (Brassica napus) in western Canada

It has been stated that soil residual herbicides, by controlling successive flushes of weeds, increase effective kill (efficacy) over the growing season, and thus impose a higher selection pressure for resistance in weeds than non-residual herbicides. To investigate this issue, the responses of wild oat to increasing rates of residual and non-residual herbicides in canola and wild oat recruitment in the following year were examined in a field study conducted in Saskatchewan, Canada, from 1997 to 2000. The rate-response curves of the wild oat variables indicated that efficacy of the soil residual herbicides, ethalfluralin and triallate, and of the non-residual herbicide, glufosinate, was generally lower than that of imazamox/imazethapyr (residual), sethoxydim, and glyphosate (non-residual). Emergence of wild oat in spring wheat (Triticum aestivum L.) grown in the following year did not differ among herbicides applied in the preceding crop year, nor was there a significant herbicide by rate interaction. The...