High hopes held for new herbicide

Jo FulwoodCountryman

Farmers faced with trifluralin resistant ryegrass in their lupin crops will soon have access to a new pre-emergent option to control weeds, according to CropCare's Jarrad Norrish.

CropCare's lupin trial at the WANTFA Cunderdin site compared the as-yet unreleased herbicide, Outlook, with trifluralin and several other herbicide mixtures.

Outlook is a Group K herbicide and has been shown to control Group D resistant annual ryegrass.

"Trifluralin resistant ryegrass is an important issue facing farmers, and this trial looked at alternative options to overcome this problem," Mr Norrish said.

"We didn't take the trial any further other than the initial showing, and the results illustrated that Outlook on its own, and when tank-mixed with Simazine, were the better performers. On its own Outlook appears to be effective on ryegrass but if there are other grasses present we encourage farmers to tank-mix with another pre-emergent herbicide to help broaden the weed spectrum.

"By controlling ryegrass populations early, this then takes the pressure off the Group A grass selective herbicides which are used post-emergent to kill the ryegrass when the crop has emerged."

Australian Herbicide Resistance Initiative director Stephen Powles said a Grains Research and Development Corporation-funded survey in 2010 of 450 random paddocks across the Wheatbelt revealed that in more than 75 per cent of cases trifluralin still controlled annual ryegrass.

"However there are worrying signs of resistance, with 25 per cent of the population showing some degree of trifluralin resistance," he said. "But for most farmers trifluralin is still working at the moment."

Professor Powles said the populations that had resistance to trifluralin were uniformly scattered throughout the Wheatbelt.

"Farmers need to diversify, when on a good thing, don't stick to it. They should be diversifying away from trifluralin, so as to keep it working, and there are good alternatives," he said.

"WA famers need only to look towards South Australia where there are far greater problems of trifluralin resistance and to learn from that, and realise that trifluralin can fail through over use."

Outlook has been registered for on-farm use in 2013 on lupins, chick peas and field peas, when sown using knife points and press wheels.

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