AUSTRALIAN farmers, struggling with an increasing amount of herbicide resistance in key problem weeds, have had welcome news with the announcement of an effective non-chemical control method for a major problem weed in the northern cropping zone.
CSIRO announced it had researched the use of a South American rust fungus as a biocontrol for flaxleaf fleabane, a broadleaf weed especially problematic in Queensland, northern NSW and the northern WA wheatbelt.
The fast spreading weed, which is now also being found in southern Australia at problematic levels, will be controlled via the release of a fungus from Colombia.
CSIRO weed ecologist Ben Gooden said the rust, Puccinia cnici-oleracei, works by infecting the flaxleaf fleabane plant and destroying plant tissue.
Dr Gooden reassured growers, who battle with rust in their grain crops annually, that the rust fungus caused no damage to crops.
"Our research found the fungus can only infect flaxleaf fleabane, while all non-target plant species tested were resistant to it," Dr Gooden said.
"Based on this research, the fungus is deemed to be safe and has been approved by the Department of Agriculture, Fisheries and Forestry for introduction to Australia," he said.
He said the discovery of the effectiveness of the rust was an important step given the ability of flaxleaf fleabane, also originally from South America, to spread quickly and its increasing resistance to a variety of herbicides.
"As flaxleaf fleabane has developed resistance to some herbicides, we hope that the biocontrol agent will be effective in reducing its populations across the country."
The trial process required extreme care to ensure the fungus was contained safely.
The fungus was imported into CSIRO's high-security quarantine facility in Canberra where scientists studied it extensively to determine if it would be safe to introduce to Australia as a biocontrol agent.
The rust will work on the flaxleaf fleabane species but not on the other major fleabane species in Australia tall fleabane.
Dr Gooden said flaxleaf fleabane was hard to control in cropping systems because of its prolific seed production.
Each plant can produce over 100,000 seeds and these can disperse long distances with the help of wind, water, animals, and vehicles, explaining its rapid spread not just within local districts but into southern and western cropping and grazing regions in recent times.
Dr Gooden said the control would not work on a similar time span to a herbicide, but instead would be a long term solution.
"You won't release the rust and find all the flaxleaf fleabane curled up and dead in a week, this is something that will work to slowly run populations down, similar to what we have seen in other biocontrol efforts such as the work on Patterson's Curse."
The Grains and Research Development Corporation (GRDC) was one of the supporting organisations for the CSIRO research.
GRDC weeds manager Jason Emms welcomed the news.
He said grain growers had been battling flaxleaf fleabane for many years and had suffered in terms of crop health and yields as the weed competed for soil water across multiple stages of the crop cycle.
"Flaxleaf fleabane can run rampant during the fallow phase as there is little competition for light or moisture and then once established it is very difficult to control," Dr Emms said.
"A biocontrol agent for this problematic weed is very exciting as it may help to reduce overall populations when integrated with existing weed management strategies," he said.
Farmers wishing to participate in the biocontrol release program should register their interest with the CSIRO at fleabanebiocontrol@csiro.au.