- Crops following cereals are at highest risk from rhizoctonia bare patch disease
- Other risk factors are poor nutrition, compacted soils and herbicide residues
- Registered fungicides are now a vital part of integrated rhizoctonia management and there are promising new fungicide seed dressings available
- When sowing wheat or barley into a paddock with a high rhizoctonia risk, cultivate below the seed to about 10cm
- Paddock trials this year will investigate liquid banding fungicide in-furrow or ‘split’ 50-50 in-furrow and at the soil surface
- When registered, it is expected these tactics could significantly improve rhizoctonia control and lift cereal yield
Fungicide seed dressings are an integral tool for managing rhizoctonia bare patch.
Trials of newly available products in WA and SA have shown a 5 per cent yield response in wheat and barley crops.
Rhizoctonia bare patch, caused by the fungal root pathogen Rhizoctonia solani AG8, is an increasing problem across the grainbelt of southern Australia.
It is estimated to reduce WA’s cereal yields by 1-5 per cent annually, worth $27 million.
All rainfall regions can be affected by this soilborne disease and incidence is likely to be high this year after prolonged dry summer and autumn conditions.
The risks will be greatest for crops following cereals and those with slow early root growth caused by low nitrogen or compaction layers.
Long term CSIRO data shows rhizoctonia can attack crops right through the growing season, not just at the seedling stage.
Recommendations to reduce the risk of yield loss from rhizoctonia bare patch include:
- Planting cereals after grass-free canola crops.
- Sowing early with soil disturbance below the seed to about 10cm to encourage early root growth.
- Using registered fungicide seed dressings in paddocks with low to moderate disease levels.
- Maintaining adequate crop nutrition based on soil test results.
Fungicide seed treatment options
Dividend® - with the actives difenoconazole and metalaxyl-m - and Rancona® Dimension – with the actives ipconazole and metalaxyl-m - are registered seed treatments to suppress rhizoctonia root rot.
In 2013, VibranceTM - with the active ingredients sedaxane, difenoconazole and metalaxyl-m - and EverGol® Prime - with the active ingredient penflufen – became available.
Extensive GRDC-funded trials by the Department of Agriculture and Food WA (DAFWA) and South Australian Research and Development Institute (SARDI) during 2011-13 found these new products can increase wheat and barley yields by an average 5 per cent, compared to untreated seed.
DAFWA plant pathologist Daniel Huberli led the WA trials at Corrigin, Kojonup, Katanning, Lake Grace, Ongerup and Salmon Gums.
These compared the effectiveness of in-furrow treatments at different rates against seed treatments at varying rates - and then a combination of seed and in-furrow treatments in wheat and barley crops.
Key findings from this research included:
- Seed treatments improved cereal yields by an average 5 per cent across the WA sites.
- Split applications of fungicide on the soil surface behind the press wheel and in-furrow 3.5cm below the seed produced the most consistent yield increases.
- In wheat, average yield response to fungicide treatment ranged from 0.1-0.5t/ha (depending on rate).
- In barley, average yield response to fungicide treatment ranged from 0.2-0.9t/ha (depending on rate).
- A promising new tool is using liquid banding fungicide in-furrow or ‘split’ 50-50 in-furrow and at the soil surface. Large scale trials of these tactics will be undertaken in WA in 2014.
- Previous WA trials of these application methods found only banding in-furrow fungicide did improve rhizoctonia control and increased wheat yields by 0.1-0.4t/ha on average and barley by 0.2-0.5t/ha on average (depending on rate).
- Banding 2-3cm below the seed with a seed treatment increased wheat yields by 0.1-0.5t/ha and barley by 0.1-0.6t/ha on average.
Full results from these WA and SA trials are contained in Daniel’s 2014 Regional Crop Updates paper at: http://researchrepository.murdoch.edu.au/21390/
Daniel says the take home messages from the trials are that in-furrow banding of fungicide 2-3cm below the seed can provide protection to crop seminal roots and surface banding behind the press wheel can protect the crown roots.
But – note – current registered products are seed treatments and are not registered for use in this way.
Daniel says there are some promising fungicide banding treatment options for rhizoctonia in the pipeline that performed well in the trials. If approved, these will not be available until at least 2015.
Syngenta and Bayer CropScience will be conducting large-scale evaluation of banding fungicides in 2014 and trial results will be on show at local field days across the GRDC growing regions this season.
In-season rhizoctonia management
Assessing crops for any impact of rhizoctonia is important as the growing season progresses. This allows an integrated management plan to be developed.
Research in WA and SA shows canola is the most useful break crop to reduce rhizoctonia levels and adding this to the rotation can translate to a significant yield increases in the subsequent wheat and barley crop.
Photo caption: DAFWA plant pathologist Daniel Huberli says there are more options for at-seeding management of rhizoctonia bare patch this year. (PHOTO: DAFWA)
Daniel Huberli, DAFWA plant pathologist, 08 9368 3836, Daniel.firstname.lastname@example.org
Daniel Huberli 2014 Regional Crop Updates paper: http://researchrepository.murdoch.edu.au/21390/
Daniel Huberli 2013 Crop Updates Paper: http://researchrepository.murdoch.edu.au/13686/
New DAFWA YouTubes on Rhizoctonia: http://youtu.be/brMxotj5jxU and Taking a Plant Sample: http://youtu.be/_hqjXWEkByg
DAFWA MyCrop Rhizoctonia information: https://agric.wa.gov.au/n/2143
GRDC Fact Sheet: Management to minimise Rhizoctonia disease in cereals - http://grdc.com.au/Resources/Factsheets/2012/03/Management-to-minimise-Rhizoctonia-disease-in-cereals
GRDC Project Code
DAS00122, DAS00123, DAS00125, CSE00150, DAW00174, UWA00152