Mitigating the impact of blackleg in canola

The challenge

The Australian canola industry has grown rapidly over the past few decades, from a few thousand tonnes in the early 1990’s to more than six million tonnes in the 2021/22 season. Now an intrinsic part of Australian cropping landscapes, canola provides both genetic and financial diversity in Australian grains farming systems that are otherwise heavily reliant on cereals.

Blackleg is the most serious and common disease affecting Australian canola crops. Without control measures, blackleg can cause yield losses of more than 90 per cent and, in some circumstances, has resulted in complete crop failure. Blackleg can evolve quickly to overcome resistance genes in cultivars and create tolerance to fungicides, so an ongoing research program to discover, develop and release genetic and agronomic management solutions has been critical to underpin industry growth.

The response

Since 2008, the GRDC and its research partners have invested more than $15 million in blackleg-specific projects. The research and development of standardised blackleg risk ratings and resistance groups has supported selection of cultivars with adequate blackleg resistance for the region, management recommendations such as maintaining 500m separation from the previous year’s stubble and basing fungicide applications on expected disease severity, genetic rating and seasonal conditions, and practical extension tools for growers such as the Blackleg Management Guide and the Blackleg management app, BlacklegCM.

Genetic tools such as molecular markers that identify individual major resistance genes and new phenotyping methods for identifying quantitative resistance have been developed and integrated in crop breeding strategies. Researchers are also gaining a better understanding of genetic resistance to upper canopy infection and this knowledge will become a crucial part of future disease management for growers.

A key current investment is the $7m National Canola Pathology Program which is helping support the canola industry and facilitate expansion of the crop into new regions. Involving researchers from the University of Melbourne, Marcroft Grains Pathology, The University of Western Australia and CSIRO, the program involves equipping growers with information to manage disease and yield loss risk.

The impact

Investment focusing on cultivars with improved resistance has led an estimated $68.75 per hectare annually in improved yield and lower control costs, and the Australian Oilseeds Federation expects Australian canola production to regularly surpass six million tonnes per year by 2025.

Marcroft Grains Pathology Principal Dr Steve Marcroft has been involved with canola disease research and extension for nearly 30 years and has seen the value of long-term investment in blackleg management.

“The area sown to canola in Australia continues to increase and this has dramatically increased blackleg inoculum loads,” he said. “As blackleg can overcome resistance genes in cultivars and develop tolerance to fungicides, we could have observed increasing yield losses each year.

“However, blackleg has not become more severe over this period, which is testament to the new genetic resources, fungicide knowledge, and cultural practices resulting from GRDC investment.

“Growers have gained a wider choice of resistant cultivars, plus better knowledge of how to deploy and maintain resistance groups, when to deploy fungicides and how farming systems impact on the disease.

“Since 2012, there have no catastrophic blackleg events such as those that occurred in the past; sound blackleg advice has given the Australian canola industry the confidence to invest and grow.”

For Landmark Elmore manager and agronomist Greg Toomey, having access to the latest blackleg groupings, ratings and pathogen testing services is critical to making informed agronomic decisions on behalf of grower clients.

“We rely on blackleg ratings and groupings for our varietal selection. We regularly monitor changes to the ratings to help us determine when a change is needed,” he said.

“We also conduct regular blackleg testing on stubble samples.

“These helped us detect a blackleg strain that had begun developing tolerance to our fungicide applications. We will carefully monitor and manage this phenomenon over the coming seasons.

“It demonstrates the importance of using a multi-faceted disease management strategy rather than simply relying on fungicides.

“The importance of the research, monitoring and extension work undertaken by Steve Marcroft and his team can’t be underestimated. Without it, there wouldn’t be a viable canola industry in southern Australia.”

Download the full case study (PDF).