The worst weed hampering West Australian crops has evolved resistance to the most common herbicide, it has been revealed.
Research by the Australian Herbicide Resistance Initiative (AHRI) at the University of WA has confirmed glyphosate resistance in three populations of wild radish, all at different locations in the state's far northern grainbelt.
Wild radish, which causes economic losses in 45 crop species in 65 countries, has evolved resistance to many other selective herbicides in WA and other cropping regions.
AHRI's Mike Ashworth said two populations are believed to have been exposed to at least one and often two applications of glyphosate, the active ingredient in Roundup, annually over two decades.
Mr Ashworth said herbicides alone should not be used to control wild radish.
Research funded by the Grains Research and Development Corporation has proven the effectiveness of non-herbicide tools including crop competition and controlling weed seeds at harvest as part of a multi-pronged weed management program.
"Growers and agronomists should use a range of tactics to control wild radish populations," Mr Ashworth said.
"The aim should be to control weed survivors, eliminate weed seed set and maximise diversity of control strategies."