Farmers growing barley in southern Australia should be on the lookout for scald — a potential disaster waiting to happen to their crop.
Franklin has previously been resistant but new strains of scald have evolved which make Franklin susceptible. Problems in South Australia indicate that Franklin's resistance is breaking down.
Senior Plant Pathologist with the South Australian Research and Development Institute Hugh Wallwork said scald would survive in stubble and cause disease in barley sown into the stubble the following year or in barley sown early.
Early in the year large numbers of airborne spores disperse from the stubble. These can travel over very long distances and can infect early-sown crops. Crops sown later — after the initial burst of spores — are less likely to become affected, although rain splash later in the season can still spread infection from stubble to plants or between plants.
Dr Wallwork said there was now a fear that the new variety Gairdner would also lose its resistance very quickly, especially if it was put under pressure.
"For this reason we are advising growers not to sow Gairdner into infected barley stubbles," Mr Wallwork said.
Seed treatment helps
"We also recommend that all barley be treated with Armour™ or Baytan™ seed treatment, although this will only provide partial control where the disease is severe. Where disease occurs, use of a foliar fungicide is advisable if the yield potential of the crop justifies the cost.
"In country with rainfall of 400 mm and above it may be worth spraying if the level of infection is high and the yield potential for the crop is good."
Mr Wallwork said he had seen a crop of Tahara triticale near Burnie in Tasmania severely affected by scald. Barley grass could also be susceptible. He advised farmers to be careful not to sow into infected triticale and barley grass stubbles.
The news from Western Australia is better.
"In Western Australia we have not observed a change in the behaviour of Franklin or Gairdner in response to scald," said Agriculture WA Senior Plant Pathologist Robert Loughman.
"In our environment Franklin is still showing useful levels of resistance," he said.
RULES OF THUMB
High-rainfall area farmers who attended recent Go-Grain research update seminars arranged by the GRDC took home these messages to help them deal with the threat of scald on barley:
- be careful with Gairdner
- use a seed treatment
- monitor the crop early — if you see infected plants spray at mid-tillering or soon after.