News & Media

New canola weed control publication now online

Released on

Released on:
Thursday, 3. September 2020 - 9:30

Canola growers now have a one-stop-shop to source information on herbicide options, with the release of the new ‘Chemical weed control in canola’ bulletin.

With a wide suite of available herbicides, an increasing risk of resistance and changing sowing practices, the bulletin provides updated advice to optimise chemical weed management strategies.

The bulletin has been produced by the Department of Primary Industries and Regional Development, with co-investment from the Grains Research and Development Corporation (GRDC).

Weeds cost Western Australian grain growers $117 per hectare on average for all crops, comprising $26/ha to yield loss and $91/ha attributed to management expenditure. 

Department research scientist Harmohinder Dhammu said weed control in canola was not only important to optimise yields but also lower the weed risk to subsequent crops.

“Canola is an important break crop in WA, so good weed control will also benefit the next cereal crop as part of the paddock rotation,” Dr Dhammu said.

“Controlling weeds in canola has become increasingly complex in recent years, with the move towards early autumn sowing, more herbicides with differing modes of action becoming available, and the risk of weed resistance developing.

“This bulletin provides information on the strategies and chemicals available to growers so they can evaluate and compare options to make informed decisions that fit their cropping program to optimise crop performance.”

The bulletin details the herbicide tolerance systems for canola in WA – conventional canola, triazine (TT), imidazoline (Clearfield®), glyphosate, and combinations of TT and Clearfield®, glyphosate and TT, and glyphosate and Clearfield® tolerance – and lists the registered herbicides, rates and advice.

It also has sections on crop topping, withholding periods, residue issues and controlling canola volunteers in subsequent crops.

Dr Dhammu said growers had a good range of control options, with a number of herbicides available for use before sowing, at crop emergence, in-crop and near maturity for specific canola herbicide tolerance systems and weeds.

“The development of ‘stacked genes’ for herbicide tolerance in canola means weed control can be tailored throughout the season by use of a selection of herbicides with different modes of action,” he said.

“There has also been a move towards earlier sowing to optimise yields, requiring early weed control to conserve moisture and nutrients, as well as reduce disease risk.

“While a knockdown herbicide can be used, often winter weeds emerge after the crop, creating a heavy reliance on in-crop or residual weed control options so it is important to understand what chemicals are available for use and when.”

Growers are encouraged to discuss with their consultant whether various weed control strategies are suitable to their situation before proceeding with treatment.

The ‘Chemical control in canola ’ bulletin is available for free here and via the GRDC website, while hard copies can be requested from department offices.


Man standing in a yellow canola crop.
DPIRD research scientist Dr Harmohinder Dhammu has been a key contributor to the new ‘Chemical weed control in canola’ bulletin, available online.

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