Download double knock fact sheet

Author: | Date: 27 Nov 2012

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A new Grains Research and Development Corporation (GRDC) fact sheet shows northern grain growers how, when and why to use double knock herbicide applications.

GRDC-funded research shows using a double knock approach in fallow paddocks gives growers a reliable technique to control difficult weeds while also assisting in the management of herbicide resistance.

The fact sheet has been compiled by Mark Congreve, ICAN.

James Clark, GRDC northern panel chair says double knock herbicide strategies are critical to reducing weed seedbanks.

“If implemented early, the double knock technique can delay the development of herbicide resistance,” he said.

“Optimal timing between applications is dependent upon the herbicides used and the weeds being targeted.

“Where possible, always target small weeds to ensure reliable performance and paying attention to herbicide application parameters will improve consistency of results.”

Mr Congreve says growers in the northern grains region have adopted the double knock approach for the following reasons:

  • to achieve very high levels of weed control that are required to stop seed set and drive down weed seed banks;
  • to delay the onset of herbicide resistance; however, this will only occur if growers implement the strategy well before resistance has developed in that field;
  • to provide improved levels of control of difficult-to-control weeds such as feathertop Rhodes and windmill grass, fleabane and sowthistle; and
  • certain combinations of herbicides need to be applied as sequential applications where they cannot be tank-mixed due to physical or biological incompatibility.

To download the GRDC fact sheet, visit



James Clark, GRDC Northern Panel Chair
0427 545 212

Rachel Bowman, Cox Inall Communications
0412 290 673

GRDC Project Code ICN00009

Region North