FARMERS in the Victorian Wimmera and the Upper South East of South Australia are set to be confronted with a fungal disease they have not seen at damaging levels since the 1970s.
Septoria tritici blotch, a fungal disease especially prevalent in wet conditions, was detected in the Wimmera at low levels last year and has built up to levels that could cause significant damage this year.
Horsham-based agronomists have confirmed they have placed extra orders of fungicide to cope with the disease.
Agriculture Victoria cereal pathologist Grant Hollaway said growers needed to be alert to the threat septoria posed.
“It is more of a stripe rust rather than a yellow leaf spot in terms of the damage it can cause,” Dr Hollaway said.
He said left untreated it could cause a 50pc downturn in yield.
Septoria has steadily worked itself into a position where it is now the major fungal disease issue in south-west Victoria.
“We plan for two sprays on the long season wheat and one for the white wheat,” said Tatyoon-based agronomist Craig Drum.
“It has really emerged as a problem over the past five or six years.”
Dr Hollaway said the major threat this year would be in areas where the disease had not been spotted for many years.
“In the high rainfall zones, the farmers are used to it and are prepared, it is more of a worry in the medium rainfall zone where they may not be expecting to see septoria.”
He said there had been confirmed reports right up into Victoria’s southern Mallee region at Rainbow.
Across the border, it is likely the disease will also push north of Bordertown and Keith in the Upper South East.
Dr Hollaway said the run of back to back wet years had led to the problem.
“Septoria was common in the Wimmera in low levels last year and this has provided the carryover of inoculum for this year,” Dr Hollaway said.
This year, he said the crop had thrived on the continued damp conditions.
“The disease requires long periods of moisture in the canopy, so it is not just a matter of the amount of rain, it relies on the number of rainy days.
“We’re in an August now where in Horsham there has been rain record 17 of 22 days of the month, so the conditions are ideal for the spread of the disease.”
Dr Hollaway said growers should look for symptoms such as pale grey to dark brown lesions which contain black fruiting bodies.
Mr Drum said the disease could be especially damaging in the Wimmera where there were high levels of stubble retention.
“Wheat on wheat rotations are at most risk and it can spread by air from neighbouring wheat stubbles too.”
He said Western District growers had been managing the disease with a spray at early stem elongation, (growth stage 31-32) with follow up with a second application at flag leaf (growth stage 39) if necessary.
With wet paddocks limiting trafficability, Dr Hollaway said growers needed to consider the possibility of application via plane on a case by case basis.
There are parallels in septoria’s reappearance after a lengthy absence with that of stripe rust, which Dr Hollaway said returned to Victoria in 2003 following a 20 year hiatus.