Western Australia
June 4, 2014
A group of DAFWA sample pots that show ryegrass resistant plants, which have been sprayed with 1.33 L/ha of glyphosate CT. Crop hygiene is crucial to prevent the risk and spread of resistant plants.
Grain growers have been urged to incorporate additional measures to combat herbicide resistance to stem the advance of emerging resistance to the most valuable weed control chemical – glyphosate.
Several recent surveys by the Department of Agriculture and Food have confirmed that resistance to label rates of glyphosate is increasing.
Department senior research officer John Moore encouraged growers to add vigilant crop hygiene to their existing herbicide resistance strategies to address the glyphosate risk.
“Glyphosate resistance in ryegrass plants occurs naturally at much lower levels than Group A or B resistances,” Mr Moore said.
“This means there are extra benefits from reducing the movement of ryegrass seeds from patches to the rest of the paddock, from one paddock to the next or from one farm to the next.
“So in addition to normal resistance management practises, growers would be wise to restrict the movement of ryegrass seeds by keeping ryegrass seed numbers low and controlling plants that survive glyphosate sprays.
“Growers should also do a glyphosate resistance test on any imported grain or produce that contains ryegrass seeds and thoroughly clean machinery or vehicles that may be contaminated with ryegrass seeds.”
A recent survey of wheat and barley from the Albany Port Zone has shown that about 60 per cent of random samples contained plants resistant to label rates of glyphosate.
This result supports a DAFWA survey across the wheatbelt earlier this year, supported by the Grains Research and Development Corporation, which found that 40 per cent of samples showed this level of resistance.
It also supports a 2011 Stirlings to Coast Farmers survey with DAFWA, which found 15 of 46 ryegrass samples with glyphosate resistance.
Mr Moore said more research was required to determine how and why the current pattern of glyphosate resistance to label rates has occurred and the gene frequencies and types in the State.
“This will provide better advice on the control of glyphosate resistant ryegrass and the strategies for other species, such as brome and wild oats, which are also showing up occasional resistance in DAFWA surveys,” he said.
Mr Moore said it was also important for growers across the wheatbelt to take action to prolong the use of all herbicides to maximise crop production and profitability.
“Growers should be ruthless about removing ryegrass surviving glyphosate treatments by using a double knock treatment with bipyridyl herbicides, rotating herbicides, burying seed by cultivation or using any other seed reduction treatment,” he said.
More information about glyphosate resistance is available at weedsmart.org.au, glyphosateresistance.org.au or agric.wa.gov.au
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