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Helping herbicides through harvest weed seed control



A ‘Story from the Field’ about a plant biology professor? Sounds a bit inappropriate, but then again, Steve Powles is no ordinary academic. He’s been involved in farming all his life and was one of the first to identify resistant ryegrass back in the 1980s. As the owner of a 300 ha farm devoted to wheat and canola cropping in Western Australia, he’s also fully aware of how severe a problem ryegrass and wild radish is for Australian grain farmers – and knows from personal experience how to manage it.

From farm laborer to leading academic

Steve Powles (66) grew up on a dairy farm in New South Wales (NSW). Remarkably for one of the world’s leading academics in his field, Steve left school at 15 after the family farm proved too small to be viable. He then worked as a farm laborer for five years before deciding to go to agricultural college, from where his academic career took off. A Rotary scholarship to Michigan brought him a master’s degree in crop science. This was followed by a PhD in biochemistry at Canberra and postdoc studies at Stanford and Paris. It was there in the early 1980s that he first became aware of herbicide resistance in weeds. His curiosity was aroused. On a 12-month grant to search for such weeds in Australia he documented the first cases of resistance after 11 months. The next grant for ongoing research was for three years, during which time ryegrass resistance in wheat exploded in Australia. “I was in the right place at the right time,” Steve says with a smile. Attracted by the prospect of establishing the Australian Herbicide Resistance Initiative at the University of Western Australia and with generous support from Australian’s Grain Research & Development Corporation (GRDC), Steve went west to take up the professorship in plant biology. But as a part-time grain farmer his farming boots are never far from his academic dress.

Managing ryegrass

“Weed resistance is a massive problem that’s reducing food production worldwide,” Steve says. “But it’s also a manageable problem, as thousands of Australian grain farmers have experienced.” Steve’s top solution to the problem is non-chemical harvest weed seed control. “Pre-1940, no grain farmer would willingly allow weed seed to return to the field,” Steve points out. “Then came herbicides and farmers just let weed seed shoot out of the back of the combine harvester before spraying the weeds with herbicide when they grew. A pretty silly ‘solution’, in my view, because you’re just adding to the weed seed bank! With ryegrass, wild radish and many other weeds worldwide, the seed is still on the plant at harvest time. So crop harvest is a great opportunity to harvest the weed seed and not eject it out of the combine harvester,” Steve explains. “There are various harvest weed seed control solutions but they all work on the principle of funneling the seed away from the chaff stream for safe disposal.” One commercialized technique Steve mentions is the Integrated Harrington Seed Destructor, which intercepts the chaff stream and pulverizes the weed seed to prevent it from entering the soil seed bank. “I know Ray Harrington well. He’s a brilliant Western Australian farmer and a great innovator and agricultural engineer.” The various harvest weed seed control techniques now available are a fine example of the fruits of close collaboration between inventive farmers and knowledgeable academics.

Non-chemical help for herbicides

In Australia there is high awareness of weed resistance because it is a massive issue for grain farmers. “In countries where there’s less awareness, it’s mainly because weed resistance isn’t impacting farmers enough. But it will,” Steve says. “Our failure to get the message across to farmers is what has disappointed me most in my career. That’s why we now spend 30% of our research budget on communication measures.” Steve is under no illusions about how severe the resistance problem is worldwide: “The golden age of herbicides is over. Back in the 1980s, new herbicides were common and resistant weeds rare. Nowadays, new herbicides are rare and resistance weeds common. The low-hanging fruit has been picked. The chemicals we still have are precious and need to be protected. That’s where I see a vital role for harvest weed seed control – in helping herbicides.”