Frequency of herbicide resistance in wild oats (Avena spp.), brome grass (Bromus spp.) and barley grass (Hordeum spp.) as determined by random surveys across south-eastern Australia

Context Wild oats (Avena spp.), brome grass (Bromus spp.) and barley (Hordeum are significant weeds of crop production in south-eastern Australia. The presence herbicide resistance these weed species is a major limiting factor on both productivity profitability.Aims We aimed to determine the distribution across Australia.Methods Several surveys were conducted randomly selected fields four states Australia over 5-year period, collecting 663 wild oats, 366 262 samples that screened for with up five different groups or subgroups.Key results In was most common clodinafop-propargyl (‘fop’ ACCase inhibitor), 22% resistant detected all regions except Tasmania. Resistance sulfonylurea herbicides (ALS inhibitors) less 7% resistant, but regionally more variable. For grass, greater proportion mesosulfuron-methyl, at 24% 19%, respectively, than quizalofop-ethyl inhibitor).Conclusions recorded three species, differences extent among regions. Overall, higher average frequency found New South Wales mesosulfuron-methyl However, some still effective samples.Implications indicates management decisions need include consideration enable successful control measures.