Promise of ‘Magical’ Weed Kill30-Jun-2014

FARMERS and advisers throughout southern Australia are delighted with a “magical” kill of problem weeds this year, but further work could lead to an even better result according to a herbicide resistance expert.

Australian Herbicide Resistance Initiative (AHRI) director Stephen Powles said the season could go from very good to excellent in terms of reducing weed seed burdens with continued focus on weed management.

“At present it’s probably a B+ or an A in terms of cutting down weed numbers, but if farmers can use some form of post-harvest control like windrow burning or a chaff cart they could turn that into an A+ and really get a lasting advantage out of the good conditions for weed control early in the year,” he said.

Rob Sonogan, Grains Research and Development Corporation (GRDC) southern panel member said farmers in his area in the Victorian Mallee had recorded great kills.

“The ultra-early break gave farmers a chance to get a good kill, it’s been fantastic for them to really get their ‘dirty’ paddocks with high weed burdens under control,” he said.

He said farmers had used double knock applications of glyphosate and paraquat in dirty paddocks to clean them up and also cut down any potential issues with herbicide resistance. Professor Powles said his previous research had showed around 66 per cent of a paddock’s ryegrass population would emerge within three weeks of a solid opening break.

He said it was a similar story with brome grass, although there has been less research done on that weed.

“It’s definitely been a fantastic chance to get your weed seed numbers down dramatically and it has also meant farmers have been able to take the pressure off specific herbicides such as glyphosate,” he said.

“This year has been a great chance to get a double knock to reduce the reliance on glyphosate, or for farmers that have been using a lot of ‘imi’ herbicides to get a rotation away from that.”

In-crop, Professor Powles recommended growers use post-emergent products they knew worked, but not to overuse any one product.
His other advice was not to skimp on label rates.

“Below label rate applications are a sure way to run into resistance problems.”

Kent Wooding, general manager at Agrivision, based in Swan Hill, Victoria, said farmers were thrilled to be able to control problem populations of rye and brome grass, along with barley grass, which is emerging as more of a problem each year.

“It’s the best knockdown in history,” Mr Wooding said.

“That really early break meant farmers had the time to wait for weed germination, get a kill and still be ahead of schedule in terms of sowing.

“Farmers may have early sown some of their better paddocks for weeds, but have waited for a good knockdown on problem paddocks.
“It’s fantastic for this area, especially when you consider up to 70pc of the Mallee’s crop goes in dry, meaning no pre-emergent knockdown, most years.”
Simon Craig, research agronomist with Birchip Cropping Group (BCG) said one of the major benefits of the early break was the chance to rest the Clearfield/Group B/imi group of herbicides.

“People have been in a bit of a loop of growing Clearfield crops here, due to residual issues – this year I would recommend people give those herbicides a spell, even in crops capable of handling them, just to give them a break.”

Queensland Country Life

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