Combining expertise to curb soil-borne disease

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Dr Friday Obanor

Soil-borne diseases might be out of sight, but as the cause of substantial damage across all crop types they cannot be underestimated

Managing soil-borne diseases is a challenge, with growers mostly reliant on implementing management techniques prior to sowing because chemical options are limited or non-existent. Yet, when the disease pathogens are well understood, success is possible. Cereal cyst nematode (CCN), once considered a major impediment to yield, can now be managed using resistant varieties and rotations with non-host crops.

Identifying the need for a strong and coordinated approach to develop better management options for soil-borne diseases, the GRDC commissioned four national projects: crown rot (led by the NSW Department of Primary Industries); nematology (led by Agriculture Victoria); molecular diagnostics (led by the South Australian Research and Development Institute (SARDI)); and the national yield response curves project (led by the Department of Agriculture and Food, WA (now the Department of Primary Industry and Regional Development)).

The first step in managing soil-borne diseases is accurately identifying the problem. Since 1997 the PreDicta® B test has allowed growers to identify diseases in their soil. The Molecular Diagnostics Centre at SARDI is working to build on the range of tests available and, with the other projects, to better understand what the numbers in the test mean to growers planting a crop in the paddock. We put this service under the microscope in stories The tool that puts a handle on soil pathogensSoil disease database a profit-protection tool, Correct sampling 'a must' to accurately expose disease risk, Reliability proven and Soil tests reveal the big picture.

Understanding how different crops will respond to soil-borne diseases is the next step. Researchers from the crown rot, nematology and yield response curves projects are working together around Australia to measure not just tolerance (defined as the impact of disease on crop yield), but also resistance (the impact of crops on how disease levels change in the soil). This information helps growers to grow a crop capable of yielding in any given year, and also to choose a crop to minimise the impact of the disease in future years.

Root lesion nematode (RLN) challenges vary depending on the location and crop mix. Starting with their distribution and importance (see Soil disease database a profit-protection tool) researchers evaluate their impact on yield and growth in the soil across Australia, from summer cropping in the north to the unique Pratylenchus quasitereoides nematode in the west (see Quantifying the impact of root lesion nematode on yields, Resistant varieties will reduce root lesion nematode numbers , Pulses differ in RLN resistance, Summer crops provide unique break crop for northern growers and P. Quasitereoides – a uniquely western issue).

Crown rot research is evaluating how different varieties perform in the presence of crown rot, integrated disease management techniques, and the impact of other diseases in combination with crown rot (Integrated management is the key to minimis).

While RLN and crown rot are major constraints on production in Australia, there are several other diseases that must not be forgotten. Summer crops have their own unique set of challenges (Summer crops provide unique break crop for northern growers and Summer crop diseases added to PreDicta® B test), CCN still needs to be managed (Cereal cyst nematode down but not out) and researchers in the west are trialling a novel approach to reducing the cost of Rhizoctonia control (Spatial mapping of rhizoctonia aims to cut fungicide costs).

More information:

Dr Friday Obanor, GRDC, 02 6166 4500,
friday.obanor@grdc.com.au