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b'A five-year survey of the entire Australian cropping belt has revealed a sobering picture of growing herbicide resistance in key cropping weeds.\\nDr John Broster from the Graham Centre for Agricultural Innovation heads up a joint herbicide resistance monitoring project between Charles Sturt University, Queensland Department of Agriculture and Fisheries and the Universities of Adelaide and Western Australia.\\nIn a 5-year cycle the group visited 3000 randomly selected paddocks and took 2000 samples of the nation\\u2019s number one weed, ryegrass, which is followed by wild radish in WA, wild oats in Queensland and NSW, and sow thistle in fourth place.\\nThe survey revealed that nationally, about 75 per cent of the populations of ryegrass are resistant to Group A \\u2018fop\\u2019 herbicides, ranging from 99 per cent in WA and 90 per cent in southern NSW around Wagga to much lower levels in western NSW where cropping intensity is a bit lower, and in northern NSW where cropping systems are different.\\nIn the last five-year survey, the level of resistance in ryegrass around Wagga was 70-75 per cent, but John says the numbers can vary as the survey monitors different paddocks.\\nBut the most concerning discovery was the increasing resistance to the most important herbicide, glyphosate. Across Australia glyphosate resistance is 5 per cent in the populations of ryegrass, but in a region like the Liverpool Plains in NSW it was in 29 per cent of the populations that were surveyed.\\nJohn says if growers lose glyphosate, they\\u2019ll have to use more complex, more expensive methods of controlling weeds.\\nHe says the key to remember is that if you use herbicides, you will get resistance.\\nBy using other methods to control plants that survive herbicide applications and prevent them from setting seed, then growers will slow \\u2013 maybe not stop, but slow \\u2013 the development of resistance to enable the use of herbicides for longer.\\nPaddocks are selected at random for the survey to provide an indication of what herbicides are still working and where, and what are at risk in the future. John says farmers generally are responsible in their management of weeds.\\nEven though there are high levels of resistance in the ryegrass to selective herbicide groups, and even glyphosate, at harvest time when researchers collect the weed seeds, most populations are below one plant per square metre.\\nSo even though it\\u2019s more complicated, he says they\\u2019re managing populations quite well using alternative herbicides and other methods than herbicides to control the weed populations.\\nFurther information\\nDr John Broster\\nHerbicide Resistance Screening\\nCharles Sturt University\\nWagga Wagga, NSW\\n02 6933 4001 or 0427 296 641\\njbroster@csu.edu.au\\nhttps://grdc.com.au/resources-and-publications/grdc-update-papers/tab-content/grdc-update-papers/2018/03/a-survey-of-herbicide-resistance-in-key-weeds-across-the-northern-grains-region\\n\\nLearn more about your ad choices. Visit megaphone.fm/adchoices'