Professor Stephen Powles – the man and the message.
PHOTO: Brad Collis
Despite extremely high rates of glyphosate resistance in weeds in North and South America, leading Australian weed research scientist Professor Stephen Powles says the chemical is still effective on most Australian farms. He says this is why careful use, along with diversity in crop rotations, and the use of integrated weed management is so important – because Australia still has the chance to prolong the effectiveness of this crucial chemical.
Professor Powles, who heads the Australian Herbicide Resistance Initiative (AHRI), based at the University of Western Australia, told growers and advisers at the Grains Research Update in Perth that 86 per cent of maize and 94 per cent of soybean crop fields in the US are sown with Roundup Ready® (RR) crops. He also said that much of the maize, soybean and cotton crops sown in Brazil and Argentina are also RR.
Before RR crops, growers regularly used a variety of herbicides with multiple modes of action. After RR was introduced, growers switched to using a single mode of action – glyphosate. As a result, a major increase in glyphosate-resistant weeds has occurred, Professor Powles says. By comparison, Australian growers still have multiple options for preserving current herbicides. These include:
- at seeding – double knock, delayed seeding, high seed rate, east–west sowing, rotated use of pre-emergent herbicides;
- at early post-emergence – ensuring a crop is healthy enough to out-compete weeds, and use of different post-emergent herbicides; and
- crop-topping at the late post-emergence stage.
In addition to these agronomic options are new or emerging technologies, in particular the integrated weed-seed destructor – an Australian innovation.
Professor Powles released results from the integrated weed-seed destructor trial conducted by former AHRI researcher Dr Michael Walsh (now with the University of Sydney) showing close to 100 per cent effectiveness for some major weeds. The GRDC has signed a commercialisation contract with de Bruin Engineering in South Australia for the integrated weed-seed destructor.
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