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Is barnyard grass the next threat to cotton?

In a recent northern region WeedSmart trial, more than twenty per cent of barnyard grass samples tested were found to be resistant to glyphosate, with another twenty per cent identified as developing resistance.

Dr Chris Preston, University of Adelaide will be speaking about residual herbicides and how to correctly use them to minimise resistance in problem weeds such as barnyard grass.

Dr Chris Preston, University of Adelaide will be speaking about residual herbicides and how to correctly use them to minimise resistance in problem weeds such as barnyard grass.

Conducted last summer, the trial tested 30 samples of suspected glyphosate resistant barnyard grass submitted by agronomists from northern NSW and southern Queensland. The results provide a snapshot of the growing problem of resistance in these areas.

Most growers and agronomists in the northern cropping areas are aware of the rising risks associated with glyphosate resistance and are keen to know what their options are for regaining the advantage. A robust residual herbicide package, combined with a knockdown or double knock, is essential to drive down weed numbers early in the crop. Growers and agronomists should work together to develop a plan to rotate and mix pre-emergent herbicides and take advantage of the new herbicides that have been registered for weed control in recent years. Plan to use them carefully to get best results and make them last.

Planning for weed control across the whole rotation is a complex business that requires growers and their advisors to be well-informed and up-to-date with the latest advances in crop and weed science.

To assist, University of Adelaide’s Dr Chris Preston delivered the latest information on best use of residual technology to combat weeds and minimise herbicide resistance when he spoke at the WeedSmart-Monsanto event ‘More cotton, fewer weeds’ on Thursday 3 December, 2015.

“Some of the earlier practices regarding residual herbicides need to be reconsidered in light of greater experience under different field conditions and changes in sowing technology,” Chris says.

“Residual herbicides on the market vary in their water solubility, ability to bind to soil components, behaviour under different soil moisture conditions and rate of degradation over time,” he says. “Unfortunately, the seasonal conditions that unfold can have a significant effect on the efficacy of any product applied.”



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Jana Dixon has joined the WeedSmart team of extension agronomists, with a focus on applying the Big 6 to manage weeds in the high rainfall cropping systems of southern Australia – from Esperance in WA to south-eastern SA, Tasmania and south-western Victoria. Jana hails from the Mid North of SA, and began working at Pinion Advisory (previously Rural Directions) while she was studying agriculture at the University of Adelaide. She has been employed full-time at Pinion Advisory since January 2019 as an agribusiness consultant, based in Clare, and spends most of her time delivering agronomy and farm business advice to clients from a wide range of cropping regions in South Australia. Pinion Advisory is a foundation WeedSmart sponsor and Jana has been involved in two WeedSmart Week events already – the first as a participant and grower group organiser at the Horsham event in 2019 and then as the local organiser for WeedSmart Week 2020 in Clare. In welcoming her to the WeedSmart team, program manager Lisa Mayer says Jana brings energy, commitment and insight to deliver communications focussed on the southern region’s high rainfall regions. “Growers in the southern high rainfall zones are facing some serious issues with herbicide resistance influencing their farming decisions,” says Ms Mayer. “Jana will be engaging with agronomists, growers and researchers in each of the distinct high rainfall zones to understand the complexities and look for practical ways to apply the WeedSmart Big 6 in various cropping scenarios.” “We plan to deliver WeedSmart Week in Esperance, part of Western Australia’s high rainfall cropping zone, in August 2021 and Jana will play a key role in the planning and delivering of our annual 3-day flagship event.” Jana says her experience with the WeedSmart program has been very positive and she has been particularly impressed with the support the program has from all sectors of the grains industry. Newly appointed WeedSmart extension agronomist, Jana Dixon (green cap) leading discussions with farm visit host, Ben Marshman, Owen SA, and growers and agronomists attending WeedSmart Week 2020 in Clare. “I have spoken to many growers and agronomists who have found real value in the information that the WeedSmart program delivers,” she says. “For many it is as much about considering another operator’s philosophy on dealing with weeds, and taking a fresh look at their own systems, rather than just learning about a new tactic or the traits of a new herbicide in isolation from the big picture.” She says the high calibre of industry people who contribute their time and expertise to the program is testament to the value WeedSmart has to agribusiness, growers, agronomists and researchers alike. 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You an follow Jana on Twitter and keep up to date with the HRZ here.
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