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Workshops get to the root of soil diseases

Rhizoctonia patches in a wheat crop
Photo: FarmLink

Conversations with growers, grower groups and advisers were the catalyst for launching an extension program that demystifies how cereal crops are diagnosed for soil-borne pathogens that cause root and crown diseases. The project was launched in 2019.

In 2022, growers and advisers at a local National Grower Network (NGN) meeting on Kangaroo Island raised concerns about the incidence and impact of soil-borne pathogens in their farming systems. In response, an NGN variation on an active GRDC project was devised and quickly launched. This mechanism allowed the relevant information to be delivered to growers in a timely manner.

The GRDC investment was a national partnership between 12 grower groups and the leading plant pathologists from state agencies.

Together, they delivered 15 interactive workshops and 15 demonstration sites designed to provide hands-on learning with live diseased plants and some management approaches for affected paddocks.

Being able to identify and diagnose soil-borne diseases requires examining plant roots and is the first step in managing these pathogens in affected paddocks.

However, the project coincided with COVID-19 restrictions that required changes to the way extension activities were delivered. Nonetheless, about 500 growers and advisers participated in the workshops and about 600 attended field days and crop walks at paddocks showcasing various diseases and control options. An additional 2000 people interacted with the extension activities online.

The project was led by FarmLink with assistance from the Grower Group Alliance in WA and the Birchip Cropping Group in Victoria.

The interactive activities included hands-on preparation and examination of live plant root systems, led by senior plant pathologists. Workshop participants were invited to bring sample plants from their own paddocks to learn how to recognise typical symptoms of various diseases caused by soil-borne pathogens.

The importance of examining the roots was highlighted since many pathogens do not cause obvious foliar (above-ground) symptoms early in their infection cycle.

Examining roots is far more revealing for diagnosis. The correct way to sample plants and wash the roots was demonstrated and a video recorded.

A series of large-plot demonstration sites were also established by the grower groups to assess the impact of various disease management options on crop performance. At these sites, DNA testing was used to accurately determine the soil pathogen(s) type and quantity, with pathologists providing guidance about management options.

These options include the use of seed dressing(s), crop rotation using break crops (where feasible), cultivation and residue management.

How to track impacts from these treatments was also discussed using observations of crop establishment, disease expression and crop yield.

Growers were also advised about factors that can complicate a pathogen’s impact on cereal crops, including:

  • a change in how symptoms of soil-borne diseases express given a shift to earlier sowing; and
  • the ability of some pathogens to co-exist and interact in ways that complicate visual identification of symptoms.

Resources produced by the project include:

  • Investment information and resources.
  • A guide to sampling.
  • A video that is more specific to Rhizoctonia:
  • A video that is more specific to root lesion nematode:

The soil-borne pathogen identification manual entitled 'A practical guide to identifying and managing cereal root diseases in South Australia' is available through the SA Research and Development Institute (SARDI).

More information: Alan Umbers, [email protected]

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