The latest scientific trial results into control options for the summer weed flaxleaf fleabane are being delivered at a leading grains research forum in Perth.
The latest scientific trial results into control options for the summer weed flaxleaf fleabane will be delivered today (17 Feb) at a leading grains research forum in Perth.
Department of Primary Industries and Regional Development (DPIRD) senior research scientist Harmohinder Dhammu said the annual to short-lived perennial weed was becoming increasingly problematic in Western Australia, likely driven by climate variability and herbicide resistance.
"Grain growers ranked fleabane as the top summer weed issue in WA at the 2025 WeedSmart event," Dr Dhammu said.
"Large plants, capable of tolerating stressful conditions due to their taproot, can persist through summer and early autumn and use substantial soil water and nitrogen if not controlled early.
"Late-spring emergence in standing crops is also increasing due to higher spring temperatures, often close to harvest when control options are limited. As a result, mature plants frequently require post-harvest treatment."
Dr Dhammu will deliver the results of screenhouse trials, along with field trials at Scadden and Walkaway, at the Grains Research and Development Corporation (GRDC) Grains Research Update in Perth.
The trials examined population-level variability in flaxleaf fleabane response to glyphosate and 2,4-D and assessed the effects of double-knock herbicide choice, application timing and spray volume on field control. They also assessed mowing, to simulate grazing, as a stand-alone tactic.
The DPIRD research, supported by a co-investment between GRDC and University of Queensland, builds on earlier work to optimise the best treatments for stressed or mature fleabane plants.
"Flaxleaf fleabane populations differed widely in their response to glyphosate, highlighting the need for resistance testing to prevent control failures," Dr Dhammu said.
"Several double knock-down herbicide programs provided near-complete control of mature fleabane and significantly reduced seed viability compared with the untreated control.
"Programs based on glufosinate or glyphosate plus 2,4-D LV ester followed by paraquat achieved 95-100 per cent control.
"In areas where phenoxy herbicides are prohibited because of sensitive crops such as tomatoes and grapevines, double-knock programs based on glufosinate mixes with glyphosate or saflufenacil, followed by paraquat + amitrole, also provided around 95 per cent control.
"Mowing, to simulate grazing, reduced biomass but did not affect plant survival and seed germinability, indicating it should only be used as a supporting tactic within an integrated approach."
