Western Australia
March 30, 2015
By GRDC western regional panel chairman Peter Roberts
Targeted management practices can lower the risk of Western Australian cereal crop losses caused by soilborne diseases such as fusarium crown rot in the 2015 cropping season.
Crop damage caused by this disease has increased in WA in recent seasons, along with losses caused by rhizoctonia bare-patch. Take-all has also been a problem for a few growers in the southern region.
If crown rot inoculum is found to be present in paddocks, the Grains Research and Development Corporation (GRDC) urges growers to implement management strategies, to prevent the disease escalating in subsequent seasons.
Grower experience in Queensland and New South Wales - where crown rot has been a significant problem for decades - has highlighted the importance of taking action early, and identified a range of management strategies to combat the disease.
Firstly growers need to know the status of the disease on their farms, keeping in mind that inoculum levels can vary across a paddock.
Secondly, depending on the status, growers and their advisers need to formulate a strategy, including decisions on rotation sequences and cereal variety selection.
Finally, it pays for growers to be aware of the full range of management strategies available to them, and to take advantage of these.
For example, Queensland and NSW growers have learnt that cultivation spreads the disease around paddocks and mixes inoculum into the soil which is where initial infection predominantly occurs.
So how do growers assess their risk and the level of management required?
Department of Agriculture and Food (DAFWA) plant pathologist Daniel Hüberli was among a panel of researchers who discussed crown rot during the recent Agribusiness Crop Updates, supported by the GRDC and DAFWA.
Dr Hüberli says it is not too late for growers to arrange testing of soil and plant/stubble samples from suspect paddocks.
This can be done through the South Australian Research and Development Institute (SARDI) PreDicta-B® pre-sowing DNA soil assay, available through accredited agronomists, or analysis of stubble/plant samples submitted to AGWEST Plant Laboratories (APL) at DAFWA.
Test results determine the level of disease inoculum in paddocks which can then be used to guide management strategies.
Seasonal conditions will ultimately determine whether elevated disease risk, highlighted by these tests, will result in crop losses.
However, results revealing high levels of crown rot inoculum indicate that to minimise the risk, growers should, if possible, plant a non-cereal break crop on affected paddocks and maintain good control of grass weeds.
For medium risk situations, growers should consider wheat varieties with the best available resistance ratings and additional management strategies such as:
- Inter-row sowing (if sowing cereals into standing cereal stubble)
- Planting at the start of the sowing window for a variety, to minimise moisture stress at the end of the season
- Balancing nitrogen and sowing rates to the yield potential of the season
- Burning stubbles (which can help reduce crown rot but will not eliminate it)
Dr Hüberli says it can take two to three years of careful management to reduce high crown rot inoculum to acceptable levels.
There is currently no registered fungicide to control crown rot, but a seed dressing has been registered for suppression. Researchers stress it should be used in conjunction with other management tools and is not a ‘silver bullet’ to control crown rot.
Dr Hüberli says grower and research experience in Queensland and New South Wales has highlighted the importance of variety selection in minimising crop losses.
For the first time this year, variety ratings for crown rot are provided in the 2015 Wheat Variety Guide, which will be available in coming weeks at www.grdc.com.au/WAWheatVarietyGuide and on the DAFWA website www.agric.wa.gov.au.
Over the last three years in DAFWA trials and in grower-sown trials, Emu Rock , a moderately susceptible variety to crown rot, has been shown to have a significant yield advantage over Mace where conspicuous levels of crown rot developed.
According to researcher Roger Lawes, of CSIRO’s Sustainable Agriculture Flagship, a dry finish to the cropping season following a fairly wet start to the season, can favour crown rot expression in crops, and this has occurred in WA in recent seasons.
Other factors favouring the development of crown rot have included continuous cereal rotations and slow degradation of infected cereal stubble.
Dr Lawes says researchers are working to determine crown rot ‘critical limits’ to help growers decide when it may be too risky to grow a cereal crop on affected paddocks.
The GRDC is funding a range of DAFWA trials to assess cereal variety tolerance to crown rot and improved management strategies through its national project ‘National crown rot epidemiology and management’.
This project is led out of the NSW Department of Primary Industries (DPI) and coordinated by the department’s senior plant pathologist Steven Simpfendorfer.
To find out more about crown rot management, access the GRDC Wheat GrowNote available at www.grdc.com.au/GrowNotes.
Agribusiness Crop Updates papers and presentations on crown rot and rhizoctonia are available on the GIWA website www.giwa.org.au/2015-crop-updates.
For additional information about crown rot management, and links to PreDicta-B® information, visit www.extensionaus.com.au/crown-rot-in-winter-cereals/, www.extensionaus.com.au/dafwa-2014-disease-and-pest-update/#Cereal or www.grdc.com.au/ManagingCrownRotWA.
Information about AGWEST Plant Laboratories is available at www.agric.wa.gov.au/n/176.
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