Australia
May 1, 2014

DAFWA plant pathologist Daniel Huberli says the risks of rhizoctonia damage will be greatest for cereal crops with slow early root growth caused by low nitrogen levels and compaction layers.

A dry summer and autumn have heightened the risk of rhizoctonia damage to Western Australian cereal crops this year, but growers can take steps to minimise losses.

The soilborne disease rhizoctoina bare patch is estimated to cause wheat and barley losses worth about $27 million each year in WA.

Rhizoctonia, caused by the fungal root pathogen Rhizoctonia solani AG8, has a wide range of hosts, predominantly cereals and grasses, and crop plants have little natural resistance to the disease.

However, ongoing research supported by the Grains Research and Development Corporation (GRDC) is finetuning management practices to control the disease.

“The risks of rhizoctonia damage will be greatest for crops with slow early root growth caused by low nitrogen levels and compaction layers,” Department of Agriculture and Food WA (DAFWA) plant pathologist Daniel Huberli said.

He said long-term CSIRO trial results showed that rhizoctonia could attack crops throughout the growing season and not just at the seedling stage.

“Research in WA and South Australia has also found that grass-free canola crops can provide useful reductions in inoculum levels - which can benefit the following cereal crop,” he said.

Dr Huberli said that aside from rotation planning, growers could control rhizoctonia by implementing management practices including:

• Controlling the ‘green bridge’ to prevent build-up of inoculum before seeding;
• Using a registered fungicide seed dressing. In recent trials conducted by DAFWA and the South Australian Research and Development Institute (SARDI), two new seed dressings registered for use on rhizoctonia increased crop yields by 5 per cent, compared with untreated seeds;
• Early sowing and soil disturbance 10cm below the crop seed using knife-points;
• Applying adequate fertiliser at seeding time, particularly nitrogen, to encourage rapid seedling growth;
• Applying foliar fertiliser once crops have emerged to address any in-crop nutrient or trace element deficiencies.

Dr Huberli said very promising results were obtained from GRDC-supported trials from 2011 to 2013 investigating new fungicides and methods of application, including liquid banding in-furrow, to reduce losses from rhizoctonia.

“Syngenta and Bayer CropScience will undertake large-scale evaluation of new fungicides and application methods in 2014,” he said.

Information about controlling rhizoctonia is available in the GRDC Rhizoctonia Fact Sheet available at www.grdc.com.au/GRDC-FS-RhizoctoniaSW

DAFWA information about rhizoctonia is available at http://youtu.be/brMxotj5jxU and https://agric.wa.gov.au/n/2143

Website: http://www.grdc.com.au

Published: May 1, 2014