Herbicide resistance opportunity knocks for WA growers

Author: Natalie Lee | Date: 22 May 2013

Paddock of green crops

Following significant rainfall in recent weeks, Western Australian growers have a golden opportunity to find out if they have glyphosate resistance in their paddocks, according to the Australian Glyphosate Sustainability Working Group (AGSWG).

The AGSWG is a collaborative initiative, supported by the Grains Research and Development Corporation (GRDC), which promotes the sustainable use of glyphosate in Australian agriculture.  

To date more than 20 cases of glyphosate resistance have been confirmed in WA’s winter grains systems.

AGSWG executive officer Andrew Storrie said large numbers of ryegrass and other weeds had germinated in WA in recent weeks and had either just been sprayed with glyphosate or would be within the next few weeks.

“Plants surviving the herbicide application will be easy to see 10 to 14 days after spraying,” he said.

Mr Storrie said any survivors should be collected and submitted for rapid herbicide resistance testing to determine whether they were resistant to glyphosate as well as other herbicide modes-of-action.

Testing can be arranged through a grower’s agronomist or farm supply agent.

“The discovery of herbicide resistance could change the way a grower needs to manage their paddocks this year,” Mr Storrie said.

As part of a GRDC Agribusiness Trial Extension Network project, the Stirlings to Coast Farmers grower group conducted a targeted survey - in paddocks where herbicide resistance was suspected - in November 2011.

A total of 46 ryegrass samples were collected from 18 properties, and 16 wild radish samples from 10 properties.

The level of resistance to glyphosate and other herbicide modes-of-action was higher than expected, with 15 samples developing resistance to glyphosate and three being fully resistant to this herbicide.

Department of Agriculture and Food (DAFWA) senior development officer Jeremy Lemon said it was interesting that there was no correlation between glyphosate resistance revealed by the survey, and a farmer’s perception of their resistance status.

“Some of those with resistant weed samples got a bit of a shock,” he said.

“A number of the growers thought they had little chance of having glyphosate resistance.

“What complicated the matter was that there were significant levels of Group A and B resistance in the ryegrass.”

With a good opportunity presenting itself with the autumn rainfall, the Esperance farm adviser ‘learning group’ will conduct herbicide resistance testing on 50 ryegrass samples from around the district in April.

The group is part of a national herbicide resistance project, initiated by the GRDC, focusing on understanding and managing herbicide resistance in glyphosate, paraquat and 2,4-D.

Group coordinator with DAFWA, Sally Peltzer, said many growers in the Esperance district had already used a glyphosate-based knockdown herbicide and would be able to see any survivors easily.

“The samples will be tested for glyphosate and paraquat resistance and growers have the opportunity to test for other modes-of-action for a modest fee,” she said.

Paired samples will be collected if there is ryegrass along the fence and in the paddock.

“The results will be in growers’ hands in four to six weeks,” Dr Peltzer said.

“If necessary they can modify their management to deal with any resistance problems found, by incorporating other herbicide modes-of-action and non-herbicide management strategies such as crop-topping or narrow windrow burning at the end of the season.

“Test results will arrive too late for those committed to canola, so if glyphosate resistant ryegrass is confirmed in paddocks where canola will be sown, late season seed set control strategies will be needed, particularly if clethodim resistance is also present.”

For more information on managing glyphosate resistance visit the AGSWG web site www.glyphosateresistance.org.au

For information on herbicide sustainability and harvest weed seed control practices, visit the WeedSmart information hub at www.weedsmart.org.au


PHOTO CAPTION: Glyphosate resistant annual ryegrass in a wheat crop.


Andrew Storrie, AGRONOMO
(08) 9842 3598
0428 423 577

GRDC Project Code ICN0009; UA00124; SCF00001

Region West