Grains Research and Development Corporation supported research is combating potentially devastating cereal diseases that threaten grower profitability and world food supplies.
Peter Wilkinson, Queensland Department of Primary Industries and Fisheries plant pathologist, says valuable trials are underway but growers are the frontline defence for diseases such as yellow spot and stripe rust.
"Even if growers have chosen resistant wheat varieties it is important to inspect crops in case a new strain or pathotype of a disease is present," Mr Wilkinson said.
"Unless the fungicide label states otherwise, apply the fungicide at first sign of stripe rust.
"However once the flag leaf has developed the fungicide will have considerably less impact on protecting yield."
Growers must adhere to pesticide label recommendations, especially pre-harvest intervals and re-entry periods, Mr Wilkinson said.
"To maximise efficacy, growers should ensure spraying equipment is in good working order and calibrated. Check that the fungicide has not exceeded the shelf life.
"Looking ahead to the 2009 season, growers should identify sources of seed for desirable varieties to plant next year."
He recommends growers diarise a time at least two weeks prior to planting to eradicate the green bridge.
Mr Wilkinson said early detection of stripe rust and yellow spot in northern NSW and southern Queensland this season did not bode well for the wheat industry.
"Yellow spot was seen towards the end of the 2007 season and, while there were no reports of economic damage in 2007, there has been a wet summer, facilitating a build up of this disease.
"Growers should be on the look out for it this season as it has already been detected in the Dalby region."
2007 GRDC-supported stripe rust trials looked at management options and compared varieties with different stripe rust reactions.
The varieties comprised EGA Gregory, with a rust resistance rating of seven, Lang, which is moderately resistant and rated five, EGA Wylie, rated four, Petrie, moderately susceptible to susceptible and rated three, and H45, which is very susceptible and rated one.
"Given the spread of stripe rust throughout the region, the timing and dosage of fungicide intervention was investigated," Mr Wilkinson said.
Two trials were done, one at Gatton Research Station and the other at Hermitage Research Station near Warwick.
Registered rates of propiconazole were compared.
Each dose was applied pre and post flag leaf emergence to each of the wheat varieties and a control left untreated.
Mr Wilkinson results showed avoiding disease is the best form of control and could be achieved by using a rust resistant wheat variety rated at least six or moderately resistant.
Mr Wilkinson said the fungicide trials showed that on susceptible varieties of wheat early fungicide application gave better results then late application.
"This is because the flag leaf and the two leaves below are the main factories for wheat yield and quality," he said.
"Protecting these leaves, preserves the yield potential of the crop."
The timing of application was more important than the dosage, as the registered high and low dosages gave similar levels of control.
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