With spring bringing emerging weed populations, now is the time to target young populations of flaxleaf fleabane for effective herbicide treatment.
Department of Agriculture Fisheries and Forestry research scientist Michael Widderick said managing flaxleaf fleabane required a strategic approach that targeted every stage of the weed’s life cycle.
Populations have been confirmed to be resistant to glyphosate, particularly in the north where the weed is well established and other tactics are needed for its control.
“When treated young, at one month or less, susceptible flaxleaf fleabane plants in fallow can be controlled with glyphosate, however quite often a glyphosate mixture or double knock is required for optimal control,” Dr Widderick said.
“A double knock approach is needed for dense infestations, especially if weeds are more than one month old.”
Best management practice for controlling flaxleaf fleabane is detailed in a new Fact Sheet from the Grains Research and Development Corporation (GRDC).
For rosette control in fallows Dr Widderick said the most consistently effective treatments were double-knocks (sequential application), particularly with glyphosate and Tordon 75-D ® followed seven days later with Spray.Seed® (paraquat plus diquat).
Dr Widderick said flaxleaf fleabane was also susceptible to several residual herbicides.
Currently registered herbicides for in-crop control of fleabane are Amicide Advance 700® (2,4-D) and FallowBoss® TORDON (2,4-D, pilcoram and aminopyralid).
“To reduce the likelihood of resistance developing use full label rates of herbicides, rotate between herbicide groups and prevent seed set of survivors.”
Aside from chemical options, increased crop competition can suppress weed growth and seed production.
“Increasing wheat crop density and using narrower row spacing decreased seed production on sprayed survivors and escapes by 90 per cent,” he said.
“Bury seed below a favourable depth for germination with a strategic soil disturbance.”
Dr Widderick said flaxleaf fleabane was established in the north and was now beginning to worry growers in the south as well.
It has become increasingly widespread since the shift to minimum tillage.
He said the weed was a prolific seed producer, with a single plant producing up to 110,000 seeds, which could disperse long distances.
“Vigilance is essential as the weed can establish in non-cropping areas. Pastures, roadlines and fencelines can often be weak links in the management chain.”
Audio download: Click here to listen to hear Michael Widderick from DAFF discussing flaxleaf fleabane control.
The GRDC Fact Sheet for flaxleaf fleabane is available at www.grdc.com.au/GRDC-FS-Fleabane
More information on managing herbicide resistant weeds is available at www.weedsmart.org.au
Dr Michael Widderick, research scientist, Department of Agriculture, Fisheries and Forestry
07 4639 8856,
Michael Thomson, Senior Consultant, Cox Inall Communications
0408 819 666
GRDC Project Code
CSU00006, DAW00158, NGA0002, ORM00001, UA00105, UA00124, UA00134, UQ00055, UQ00062