CROWN rot often gets the blame for high screenings and low yields in a dry finish to the season.
And, with closer cereal rotations and increased stubble retention, the disease has emerged as an important one for grain growers.
In Victoria, crown rot causes yearly average yield losses in wheat of 2.6 per cent and up to 20 per cent in some crops.
During 2008, crown rot reduced the state's wheat yields by 3.2 per cent, costing $20 million.
In southern NSW, yield losses in bread wheat have varied from 3-60 per cent.
Research plant pathologist Andrew Milgate, of Wagga Wagga, said crown rot of wheat was carried over on infected plant material.
Wet winters enable the fungus to grow from infected stubble to wheat seedlings.
Dr Milgate said losses from crown rot were greatest in durum wheat.
Bread wheat was more tolerant than durum but could still suffer significant yield loss, he said.
"In some seasons, barley matures before the onset of moisture stress, escaping the effects of crown rot, but in other seasons it can suffer losses," Dr Milgate said.
Yield loss is associated with the levels of crown rot inoculum in a paddock before sowing.
Identifying those "risky" paddocks was critical in its management, Dr Milgate said.
This may involve a PredictaB root-disease test before sowing.
Dr Milgate said crown-rot levels could be reduced by sowing non-cereal crops.
Victorian Department of Primary Industries studies have shown two years of break crops were needed to keep crown rot inoculum at safe levels.
Variety ratings for crown rot are based on resistance.
But even moderately resistant varieties sown into moderate to high levels of inoculum could see yield losses of up to 50 per cent.
"Early management decisions are the key," Dr Milgate said.
"Fallow, field peas, medic, vetch and canola crops have been shown to be effective at reducing inoculum loads, given there is enough rainfall to decompose stubble.
"But a one-year break crop is not enough under high crown rot levels."
