NSW Government plant pathologists are developing solutions to manage an emerging fungal disease that threatens the production of barley — the state's second-largest cereal crop.
The NSW Department of Primary Industries and Regional Development (NSW DPIRD) and the Grains Research and Development Corporation (GRDC) are co-funding a project to understand the epidemiology of Ramularia leaf spot (RLS) in barley.
NSW DPIRD Plant Pathologist Dr Ben Ovenden, based at the Wagga Wagga Agricultural Institute, has been conducting field experiments on infected crops during the past two years.
He said the fungal disease, which was genetically recorded in NSW in 2019 but only detected in the field in 2021, is one of the most intriguing he has encountered throughout his career.
"Ramularia poses a significant threat to barley production, but it is not well understood in Australia," Dr Ovenden said.
"It's hard to detect, it's transmitted via seed and windborne spores, and it can produce billions of spores per hectare to infect crops over large areas.
"From a control point of view this disease is challenging because there are so many aspects that we need to solve."
Through his research, Dr Ovenden said RLS appears to impact grain quality and can result in average crop yield losses of more than 10 per cent.
RLS is now endemic across the state's barley crops and is more prevalent in higher rainfall areas throughout the central west and southern regions.
Field experiments demonstrated that fungicide treatments effectively reduced disease severity and preserved grain yield, with significant differences noted between treated and untreated plots.
However, the fungus can grow symptomless within the plant but develops into a pathogen late in the season when it multiplies rapidly, producing a toxin that causes all parts of the plant to decay and die.
"This happens right at the end of the growing stage after flowering, usually a month before harvest when many farmers have finished detailed crop checking, so the disease is often not even recognised," he said.
"Even if the disease is diagnosed once symptoms appear, then it's too late to apply fungicide — it's not going to provide a yield benefit, and other problems arise with withholding periods for food production or livestock consumption."
Through the long running GRDC National Variety Trials, Dr Ovenden and his team have provided a disease rating for RLS across all the current Australian barley cultivars and the new breeding lines that will become available.
He said all domestic cultivars of barley are susceptible to the disease and none display any genetic resistance.
Another challenge is that the disease has developed fungicide resistance to all three major modes of action overseas.
"Available fungicide controls in Australia are limited and costly, so it is important to explore how to maximise their effectiveness and manage resistance," Dr Ovenden said.
"There's no silver bullet to protect your crop from one year to the next."
GRDC Manager Diseases Dr Alan Little said the organisation's investment, which has been supporting the research since late 2023, was helping to close critical knowledge gaps around yield and revenue losses.
"Accurate identification of RLS is vital for effective crop management. This study has been investigating the fungal pathogen responsible, exploring its genetic and population diversity, disease incidence, environmental triggers, and potential regional patterns," Dr Little said.
"Having robust identification tools will allow growers to take timely action, reduce misdiagnosis, and minimise yield losses.
"Understanding the disease's epidemiology and economic impact will guide future investment in targeted management strategies to support growers."
Crops affected by RLS start displaying symptoms in early October in most regions. NSW growers who suspect their crops have the disease and need diagnostic support can send samples to the NSW DPIRD Wagga Wagga Agricultural Institute or call 02 6938 1999.
