Research sheds light on Rhizoctonia control
The use of break crops significantly reduces Rhizoctonia inoculum levels, but this beneficial effect lasts only until the end of the following cereal crop.
This is one finding from research supported by the Grains Research and Development Corporation (GRDC).
The research into the damaging root disease was conducted by CSIRO Sustainable Agriculture Flagship and the South Australian Research and Development Institute (SARDI).
Rhizoctonia (R. Solani AG8) is a soil fungus which damages crops by pruning the root system, resulting in water and nutrient stress to the plant, and characteristic ‘bare patches’ in paddocks.
Rhizoctonia bare patch costs grain growers $59 million in cereal losses each year, mainly in the low to medium rainfall regions across southern Australia.
Project supervisor and CSIRO senior research scientist Vadakattu Gupta said the research confirmed that cereals were the key host for the rapid build-up of Rhizoctonia inoculum – the source of the disease.
“It is therefore important to use break crops or ‘weed-free’ fallow, which have similar impacts on inoculum levels,” he said.
“Inoculum levels in soil after canola and other non-cereal break crops are lower than before these crops,” he said.
“These lower levels are maintained through to the end of the next summer, therefore reducing the risk of Rhizoctonia damage to the crop grown in the year following the break crop.
“Inoculum levels following wheat after rotation crops returned to original levels.”
Dr Gupta said the research also confirmed that tillage reduced Rhizoctonia inoculum levels but the effect depended on the time of tillage and soil type.
“In field trials in 2009 and 2010, no-till and strategic cultivation resulted in the highest levels of Rhizoctonia inoculum, while conventional cultivation had the lowest,” he said.
Dr Gupta said the research also found that the amount of Rhizoctonia inoculum in soil could change dramatically throughout the year.
“Changes in Rhizoctonia inoculum, both in-crop and during the non-crop period, are far more dynamic than previously believed,” he said.
“Rhizoctonia inoculum build-up continues through to maturity in a crop, especially in the surface 0 to 5cm zone.
“Long, dry periods over summer can allow inoculum to build up, while rain post-maturity of a crop causes a decline in inoculum, and major rainfall events over summer can substantially reduce inoculum.
“These trends were observed both in the southern and western agricultural regions.”
The project involved field trials mainly in South Australia and New South Wales, but also included a WA component – mainly to determine the dynamics of pathogen inoculum during summer months.
Caption: CSIRO senior research scientist Vadakattu Gupta at a research site near Avon in South Australia.
• GRDC Project Code: CSE00048
• This media release and other media products are available via www.grdc.com.au/media
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