Septoria Tritici Blotch (STB) in wheat.

A WET winter in southern Australia has seen an increase in the prevalence of the region’s most significant wheat disease, Septoria Tritici Blotch (STB).

The foliar fungal and stubble borne disease can cause yield losses of up to 60 per cent in susceptible wheat varieties and is particularly problematic in cool, wet seasons.

Significant winter rainfall and forecasts for a wet spring have made it important for growers to monitor paddocks and consider management options for STB this season. Many have now started fungicide applications as part of integrated disease management strategies.

But going forward, their on-farm decision making may be enhanced by research from two new Grains Research and Development Corporation (GRDC) investments designed to improve growers’ knowledge and management of STB.

GRDC crop protection manager – South, Ruth Peek, said STB was a major disease of wheat, particularly in the high and medium rainfall zones of the southern region, and could be costly to manage particularly in a season like this one.

“The incidents and distribution of STB have increased in recent years, largely due to intensive farming practices, which have led to a build-up of inoculum,” Ms Peek said.

“In the southern region in 2019, GRDC’s national grower network (formerly the Regional Cropping Solutions Network) listed STB as the most important crop disease for wheat, which reflects the high level of industry concern.

“The other challenge is that we know the STB pathogen has the potential to rapidly evolve and develop fungicide resistance or insensitivity in its populations.”

Investment in research

In response, GRDC recently initiated two major research investments into STB.

The first is a three-year project, which will investigate the epidemiology of STB in low and medium rainfall zones to better inform integrated disease management strategies. The research will be led by Grant Hollaway from Agriculture Victoria and his colleague Hari Dadu, in collaboration with Tara Garrard from South Australia Research and Development Institute (SARDI).

Trials as part of this project will be conducted by Agriculture Victoria and Birchip Cropping Group at Horsham, Hamilton, Watchupga and Longernong, and in South Australia at the Waite Campus, Hart Field Days site and the Upper North Farming Systems site near Booleroo Centre.

“The aim of this project is to improve our understanding of the conditions that are likely to result in economic impact from STB and identify integrated disease management strategies growers can use in the medium and lower rainfall zones,” Ms Peek said.

GRDC’s second investment into STB is focused on the high rainfall zone and led by Field Applied Research (FAR) Australia’s Nick Poole as part of current GRDC-supported research into hyper yielding crops.

Trial work will be conducted at Gnarwarre in Victoria, Millicent in South Australia and Hagley in Tasmania over the next two years.

Ms Peek said this project aimed to demonstrate integrated disease management strategies for STB in the southern high rainfall zone, specifically key tactics to guide grower decision making and risk aversion through variety choice, stubble management, optimal and conservative fungicide application and timing.

“The adoption of integrated disease management for STB in the high rainfall zone will hopefully reduce regional inoculum levels, in turn reducing the amount of fungicide being used in the region and therefore the risk of resistance developing,” she said.

The STB integrated disease management strategies will be included in the program for the 2021 Hyper Yielding Crops (HYC) field days:

• Gnarwarre, October 14 at the Victorian Crop Technology Centre, Gnarwarre.
• Millicent, October 28 at the SA Crop Technology Centre, Millicent.
• Hagley, November 18 at the Tasmania Crop Technology Centre, Hagley.

Source: GRDC