THE PRESENCE of branched broomrape in Australia poses a significant threat to the nation 's export trade in agricultural and horticultural products, because many countries will not buy produce that could contain broomrape seed.
While branched broomrape does not attack cereals, it can be hosted by broadleafed weeds, opening the way for grain contamination with the minute, dustlike seeds.
Other export crops under threat, either from direct infestation or seed contamination, include oilseeds, pulse crops, hay and vegetables.
Broomrape also has the potential to slash production of broadleafed host crops.
The weed was identified in the SA Mallee during 1992, prompting a national decision to eradicate the parasite as the best means of protecting Australia's rural industries and export trade. The eradication initiative is being managed by the Sustainable Resources Branch of the SA Department of Water, Land, Biodiversity and Conservation.
According to Philip Warren, Manager of the Branched Broomrape Program, the first step was to quarantine all areas where the weed had been identified, to stop it spreading.
That involved imposing tough restrictions which have had a big impact on the protitability and emotional well-being of farmers in the area, Mr Warren said. "A handful of farmers in the quarantine area are, through no fault of their own, carrying a financial, practical and emotional burden on behalf of farmers throughout Australia.
"We believe the quarantine restrictions have limited the weed's spread and given the team time to develop a program aimed at eradication."
Researchers initially drew on overseas experience and trial results, but a range of trials specific to Australian crops and weeds in the area where the pest has been found are starting to produce results.
Research on soil conditions, response to herbicide
Branched broomrape appears to be most prolific on host plants growing in freedraining alkaline soils that are low in nitrogen. Researchers have established its host range and trials indicate it is susceptible to low rates of some conventional herbicides.
However, effective chemical control requires excellent timing, as the plant emerges and matures in around a fortnight. The team is now turning its attention to integrating this new knowledge into local farming systems while developing methods of running down the plant's seed bank.
Anyone who thinks they may have branched broomrape on their property should contact the relevant government department:
Commonwealth 02 6271 6534; NSW 1800680244; NT 08 8999 2375; Queensland 132 523; SA 08 8303 9500; Tasmania 1300 368 550; Victoria 0397850111; WA 1800068107.