ChileanJAR

Several experiments were carried out in Southern Chile to evaluate resistance of two grasses to herbicides. A Lolium rigidum population from the VIII Region and two Avena fatua populations from the IX Region, suspected to be resistant to some herbicides that inhibit the biosynthesis of lipids, were sprayed with commercial herbicides at two application doses, the recommended dose and the smaller dose commonly used by farmers. When recommended herbicides for lupin (Lupinus albus L.) and oilseed rape (Brassica napus L.) were applied, the three populations showed resistance to aryloxyphenoxy propionate, quizalofop-p-tefuril, haloxyfop methyl, quizalofop-p-ethyl and fluazifop-p-butyl herbicides. Nevertheless, there was no resistance to cyclohexanedione, clethodim and sethoxydim herbicides. When recommended herbicides for wheat (Triticum aestivum L.) were applied, the three populations showed resistance to aryloxyphenoxy propionate, diclofop methyl, clodinafop propargyl, cyclohexanedione herbicide, and tralkoxydim herbicides. There is concern over the level of resistance reported, since applications of herbicides at normal doses did not reduce fresh weight values compared to the control with no herbicide applications, except for wild oat populations, which presented less resistance to tralkoxydim than diclofop methyl and clodinafop propargyl. Wild oat and annual ryegrass populations lacking resistance used as controls were susceptible to all the herbicides applied.