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Problem Weed on GRDC’s ‘Wanted’ List

25 August 2011

AUSTRALIA - Windmill grass and has been named by the Grains Research and Development Corporation's (GRDC) as among the top five problem weeds of the northern grains region.

The weed continues to establish itself in Central West NSW and scientists fear it may threaten the benefits gained from minimum tillage farming systems.

Maurie Street, chief executive officer of the Dubbo-based and GRDC-funded Grain Orana Alliance (GOA) says some effective herbicide control options have been identified, including the “double knock” technique.

“Windmill grass has been confirmed as glyphosate resistant and is quickly becoming one the region’s most problematic weeds in zero tillage summer fallows,” Mr Street said.

“The use of herbicides which are generally not effective has seen the weed infest paddocks at an ever increasing rate and the recent identification of glyphosate resistance adds further to the difficulties of control.

“Final control levels in the research outcomes have depended on moisture availability before, during and after spraying but double knock treatments have shown to be essential for options to be effective.”

Mr Street says further work by GOA this year will compare glyphosate formulations as well as a number of other aspects important in herbicide control of windmill grass.

“The recent identification of glyphosate resistance in windmill grass and control problems has seen the weed attracting attention of such bodies as the Australian Glyphosate Sustainability Working Group (AGSWG) and other researchers.

“We will see an increased focus on developing our understanding and controlling this problem weed both locally and from a national perspective.”

Mr Street says windmill grass has rapidly increased in prominence in CW NSW cropping paddocks over the last four to five years, especially in zero tillage systems.

Suspected causes of this have been reinforced by recent survey work by GOA, he said.

“These results have highlighted the vulnerability and linkages between systems using single mode control techniques and development of herbicide resistance in windmill grass.

“The survey work clearly linked this weed’s prominence with the removal of grazing and cultivation from the cropping system and total reliance on ineffective herbicides namely glyphosate for control.”

Past trial work in Western Australia has shown that it can cause yield penalties of 0.3 tonnes per hectare in wheat where left uncontrolled.

Mr Street says anecdotal evidence in CW NSW shows severe cases resulted in yield penalties of more than 50 per cent.

“Windmill grass has shown to be very difficult to control in zero tillage systems with herbicides,” he said.

“As such it challenges these systems and threatens to see a need for cultivation to control it. This could jeopardise or at least reduce many of the gains that zero tillage systems have offered.”

TheCropSite News Desk

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