Pre-seeding paddock sampling to detect the presence of soilborne diseases and pests takes on renewed importance this year.
The recommendation to test suspect paddocks comes on the back of evidence of increased levels of fusarium crown rot, take-all, rhizoctonia bare patch and root lesion nematodes (RLN) across many parts of WA.
A blanket management strategy can’t be used for all soilborne diseases and pests, so it is vital to know what’s in the paddock by using soil and stubble testing services.
This can help with rotation planning for 2015, as consecutive cereal crops are at the highest risk of yield losses and crop and variety choice following cereals is a major management strategy to break disease and pest cycles.
The 2015 Agribusiness Crop Updates, hosted by the Grains Research and Development Corporation (GRDC) and the Department of Agriculture and Food (DAFWA) at Crown Perth on February 24 and 25, will have a major focus on the latest GRDC-funded research into control and management of soilborne pests and diseases.
Testing for soilborne diseases and pests in 2015
The South Australian Research and Development Institute (SARDI) PreDicta-B® DNA-based soil test is available from February to June through accredited agronomists.
It can detect the presence of common fungal crown or root disease pathogens (including take-all, rhizoctonia bare patch and crown rot) and nematode pests (including some RLNs) in suspect paddocks.
High risk paddocks that are ideal for testing include those where: bare patches, uneven growth or whiteheads were noticed in last year’s cereal crops; yields were unexpectedly poor last year; cereals followed cereals or grassy pastures; or where land has been newly purchased/leased.
The major recent change to the PreDicta-B® testing service involves the addition of stubble pieces to the soil sample. Sampling guidelines include:
- Collect three cores (1cm diameter X 10cm deep) from each of 15 different locations in the target paddock or sampling zone
- Take cores from along the rows of previous cereal crops if visible and retain any stubble collected by the core
- Add one piece of cereal stubble (if present) to the sample bag at each of the 15 sampling locations. Each piece should include the segment from the crown to the first node (discard material from above the first node)
- Maximum sample weight should not exceed 500g.
The e-version of the PreDicta-B® root disease manual has been reformatted for easier use on mobile devices and can be downloaded by accredited agronomists.
Through its Soil Biology II initiative, GRDC-funded research is also continuing into broadening the range of tests available through PreDicta-B®.
Testing soil and stubble samples to correctly identify soilborne diseases and pests can also be carried out by the Department of Agriculture and Food, Western Australia’s (DAFWA) diagnostics service, AGWEST Plant Laboratories (APL).
It is important to send whole plants – including intact root systems and soil – for healthy and suspect samples.
Healthy soils to feature in Crop Updates program
Latest breakthroughs in research to control and manage soilborne fungal diseases will be presented at the Agribusiness Crop Updates.
DAFWA plant pathologist Daniel Hüberli and Trevor Klein, of Syngenta, will focus on Rhizoctonia solani AG8 and management of crown rot.
DAFWA researchers Martin Harries and Greg Shea and CSIRO’s Roger Lawes will outline key findings from the WA Focus Paddock project, which – among other things – has been tracking soilborne disease and pest incidence in 184 paddocks across the State for the past five years.
The Focus Paddocks have shown that, generally, levels of disease detected using PreDicta-B® on WA soils have been low (the majority of the focus paddocks have had DNA levels below detection or at levels associated with a low risk of yield loss).
But, the incidence and severity in paddocks with pathogen DNA detected has increased during the study period - for most pathogens in medium and high risk areas.
Martin Harries says the highest DNA levels were recorded before sowing in 2014, after the dry 2013-14 summer, and the southern region had higher soil DNA levels for most pathogens.
He says crop species and rotation sequences affected disease levels.
When canola or pasture was in a paddock, the level of the RLN Pratylenchus neglectus DNA in soil increased during the growing season. This indicates canola and pastures are a host for this nematode.
In lupin and field pea paddocks, levels of P. neglectus DNA decreased.
As WA growers are switching from pulses or lupins to canola for a break crop, the researchers warn there is a potential risk of increasing RLN issues.
The Focus Paddock results for rhizoctonia bare patch found canola was the only species to suppress this pathogen during the growing season.
Martin says this indicates that sowing canola in paddocks with a high risk of yield loss to rhizoctonia would be a good strategy.
The Focus Paddocks are part of the GRDC-DAFWA Putting the Focus on Profitable Crop and Pasture Sequences in WA project and involve a collaborative effort with the grower groups: Liebe, Facey, WA No Tillage Farmers Association and Mingenew Irwin Group.
This project will continue in 2015 and more localised information from the Focus Paddocks will be presented at Regional Crop Updates across WA.
2015 Soil disease resistance ratings
Latest crop variety disease resistance ratings, including for new 2015 releases, can be found on the National Variety Trials (NVT) website and the ‘Crop Diseases: forecast and management’ section of the DAFWA website (see ‘Useful Resources’ below for links).
Crown rot resistance ratings will be included in the 2015 Wheat Variety Guide.
The GRDC’s eXtensionAUS information hub also contains the latest information about crown rot management.
Melissa Williams, Cox Inall Communications
042 888 4414