Herbicide resistance in barley grass populations from the low rainfall zones in South Australia

Why do the trial?Barley grass possesses several biological traits that make it difficult for growers to manage in the low rainfall zone, so it is not surprising that it is becoming more prevalent in field crops in SA. A survey by Llewellyn et al. (2015) showed that barley grass has now made its way into the top 1 0 weeds of Australian cropping in terms of the area infested, crop yield loss, and revenue loss. In this survey, barley grass was ranked as the 7th most costly weed to control by the growers in SA and VIC Mallee and Mid-North, Lower Yorke and Eyre Peninsula. In a previous random survey in SA in 2012, Shergill et al. (2015) identified resistance to quizalofop in 15% of barley grass populations from Upper North and Eyre Peninsula. Additional herbicide-resistant populations have been identified since the previous survey. Growers in these regions have observed many control failures and have been collaborating with this GRDC-funded project to confirm the resistance status of their barley grass populations.