Background
What is the weed problem?
Flaxleaf fleabane is one of the most difficult weeds to control in the northern New South Wales and southern Queensland regions, and is also becoming widespread within the southern and western grain-growing of Australia. The increasing relative abundance of this weed has been attributed to the practice of minimum tillage, as this system creates a better environment for seed germination and survival. Flaxleaf fleabane affects crop production as it greatly reduces stored water supplies in fallows which affects subsequent crop emergence and growth. This species is also a prolific seed producer that can produce up to 120,000 seeds per plant. The size and morphology of the seeds enable them to dispersed long distances by both wind and water.
Features of flaxleaf fleabane, A) late stage rosette prior to bolting, B) fine hairs coving the stems and leaves, C) the fluffy cream-coloured seed heads and D) the seed with a tuft of fine bristles.
How is the weed currently managed?
Flaxleaf fleabane is currently managed with a combination of chemical and cultural strategies. Populations of flaxleaf fleabane have evolved resistance to multiple herbicides including glyphosate, paraquat, atrazine, simazine, chlorsulfuron and diquat. Herbicide resistant populations are typically managed using control strategies that include rotation of different chemical herbicides integrated with cultural control methods. Cultural control options include increasing species richness and diversity, decreasing row spacing of crops, and strategic use of tillage to invert the soil and bury seed below 2 cm depth. These techniques are not always viable as they may run contrary to current agricultural practices (e.g. minimum tillage farming adopted to minimise top soil loss).
Flaxleaf fleabane in a sorghum crop, Bowenville Queensland (photo courtesy of M. Widderick QDAF).
What can biocontrol offer to the weed’s management?
Biological control would offer an additional tool for the management of flaxleaf fleabane across the broader landscape, not just in agricultural situations. A successful classical biological control program for flaxleaf fleabane would reduce the need and/or frequency of other weed management tactics, especially during fallow. In a crop situation, it could potentially reduce yield losses by suppressing the competitive effects of the weed. By reducing the capability of the weed to reproduce, biological control agents could slow the spread of flaxleaf fleabane both within and outside of cropping areas and hence reduce the frequency of re-infestation.