Biological suppression may cut root disease losses
GroundCover™ Issue: 98 | 27 Apr 2012
- By Sharon Watt
Researchers are examining the behaviour of a complex root disease, Rhizoctonia, to help reduce the estimated $60 million in lost production each year in the southern grain-growing region.
The GRDC-funded study being conducted by CSIRO and other research partners has revealed that the soil-borne Rhizoctonia solani AG8 fungus causes damage by pruning newly emerged crop roots. This has been shown to affect crops from emergence to maturity, resulting in water and nutrient stress to plants. Severe infection generally manifests as patches of poor crop growth.
The research involves a focus on how the environment and management practices influence levels of Rhizoctonia inoculum that initiate the disease and the extent of infection in cereal crops.
CSIRO scientist Dr Gupta Vadakattu says Rhizoctonia root rot is difficult to control for several reasons. “The fungus can grow and survive in the soil without a live plant host, it has a wide range of hosts and there are no resistant cereals,” he says.
“It is also strongly influenced by soil and environmental conditions, which mean the seasonal impacts are hard to forecast.”
Dr Vadakattu says measures targeting both the Rhizoctonia inoculum and the infection itself are needed to help control the disease.
He says non-cereal break crops can assist growers in reducing inoculum levels, which are usually the highest following cereals and the lowest after canola and mustard crops. However, lupins are said to be the least effective in reducing the Rhizoctonia inoculum.
The research shows that rain post-harvest can substantially reduce inoculum in the soil, while multiple rains in summer and autumn also tend to lower inoculum levels.
Dr Vadakattu says factors that reduce crop root growth, such as cold or compacted soils, poor nutrition and herbicide residues, are likely to increase Rhizoctonia damage.
He says the ability of soil microorganisms to suppress Rhizoctonia has been identified in a range of soil types, and this can help provide long-term control of the disease.
Researchers are working to improve knowledge of this ‘biological disease suppression’ to better manage Rhizoctonia in the future.
A GRDC Fact Sheet outlining Rhizoctonia research findings, ‘Management to minimise Rhizoctonia disease in cereals’, is available at www.grdc.com.au/GRDC-FS-RhizoctoniaSW.
GRDC Research Codes DAS00125, CSP00150, UWA00152
Dr Gupta Vadakattu,
08 8303 8579
GRDC Project Code DAS00125, CSP00150,
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