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Latest on Cereal disease – 2015 GRDC Update papers

Keep up with the latest research information on Cereal diseases including Septoria tritici blotch of wheat, spot and net blotch of barley, rhizoctonia root rot, crown rot and the cereal rusts. The following update papers were presented at the GRDC Updates across Australia in February and March 2015.

Click the paper titles to view the full papers.

Southern

Biology and management options for control of Septoria tritici blotch and Net form of net blotch

By Hugh Wallwork (SARDI). Presented at Adelaide, February 2015.

  • Septoria tritici blotch (STB) is increasing in the south east of SA as a result of intensification of wheat cropping. The pathogen population in the south east may differ from elsewhere in SA.
  • Septoria is best controlled with variety resistance, but later sowing and fungicide treatments can also be effective for avoiding crop damage.
  • No new virulences in Net form net blotch (NFNB) were detected in 2014 but the disease remains a threat to many barley varieties. The resistance in some varieties appears more durable and should be protected by growers by avoiding the use of the most susceptible varieties.

Cereal root disease management in Victoria

By Grant Hollaway, Joshua Fanning, Frank Henry (Department of Economic Development) and Alan McKay (SARDI). Presented at Ballarat, February 2015.

  • Minimise losses associated with root diseases by inspection of plant roots in the previous crop or using a PreDicta B soil test prior to sowing to identify at risk paddocks.
  • Crown rot will be an important disease during 2015 if the season finishes with a dry spring as inoculum levels are high from the 2014 season. Reduce risk by rotating to non-cereal crops.
  • In paddocks with high numbers of root lesion nematodes, yield losses can be minimised by selecting partially tolerant cultivars and avoiding late sowing. Resistant cultivars can reduce nematode densities and therefore reduce losses in subsequent intolerant crops.
  • Cereal cyst nematode is a very damaging nematode if numbers are allowed to increase by growing susceptible cereals.
  • Rhizoctonia root rot will likely be a low risk in 2015 if there is a wet summer with multiple rainfall events, provided summer weeds are controlled.
  • Take-all will be a low risk in 2015 as the dry spring in 2014 would have limited inoculum build up, while rainfall during January 2015 will have reduced inoculum further.

Spot form of net blotch yield loss and management in barley using fungicides and resistance in Victoria

By Mark McLean and Grant Hollaway (Department of Economic Development). Presented at Ballarat, February 2015.

  • Spot form of net blotch (SFNB) caused up to 25% loss in grain yield and quality in very susceptible barley varieties during 2014.
  • Varieties rated moderately susceptible or better to SFNB had significantly less grain yield and quality loss than susceptible varieties.
  • Foliar fungicides provided effective suppression of SFNB when applied at Z31 and/or Z39.
  • A new seed applied fungicide provided very good suppression of SFNB during the early stages of crop development.

New developments in PreDicta B and management of rhizoctonia root rot

By Shawn Rowe, Marg Evans, Paul Bogacki, Sjaan Davey, Alan McKay (SARDI), Jack Desbiolles (University of South Australia), Gupta Vadakattu (CSIRO), Steven Simpfendorfer (NSW DPI), Daniel Hüberli, Miriam Connor, Bill MacLeod (DAFWA), Robert Battaglia, Leanne Forsyth, Trevor Klein (Syngenta Australia), Mike Clarke, Geoff Robertson (Bayer CropScience) and Ray Correll (RHO Environmetrics Pty Ltd). Extra technical comment by Protech Consulting Pty Ltd. Presented at Ballarat, February 2015.

  • When collecting PreDicta B samples, add 1-2 pieces of stubble from base of old cereal or grass weeds per sampling location (typically 15, about 5-7 cm long) within the paddock. Core along the rows of the previous cereal crop and do not remove any plant debris.
  • The GRDC project DAS00137 has been established to improve the value of PreDicta B to grain producers. This includes improving the risk categories for crown rot and root lesion nematodes in collaboration with National crown rot and nematode programs DAN00175 and DAV00128, respectively, plus broadening the range of tests and fast tracking these onto PreDicta B reports. See SARDI website from mid March for more detail.
  • Uniform® applied either by liquid banding or coated fertiliser has been registered to control rhizoctonia root rot. Banding treatments produced greater and more consistent yield responses than Vibrance® seed treatment. Dual banding of Uniform® in-furrow 3-4cm below the seed and on the surface behind the press wheel gave the most consistent yield and root health responses across seasons. Responses in barley were greater than wheat; responses also appear to be greater in seasons with good spring rainfall. The influence of season needs further investigation.
  • BYF14182 banded in-furrow achieves similar yield responses to EverGol® Prime seed treatment. Banding BYF14182 in-furrow combined with EverGol® Prime seed treatment significantly improved root health; APMVA registration of BYF14182 for in-furrow application is pending.

Western

Rhizoctonia solani AG8: New breakthroughs in control and management

By Daniel Hüberli, Miriam Connor, Bill MacLeod (DAFWA), Robert Battaglia, Leanne Forsyth, Ben Parkin, Trevor Klein (Syngenta Australia), Mike Clarke, Geoff Robertson (Bayer CropScience), Ray Correll (Rho Environmetrics Pty Ltd), Jack Desbiolles (University of South Australia), Paul Bogacki and Alan McKay (SARDI). View Daniel’s powerpoint presentation (PDF 2.3Mb), Perth, February 2015.

  • The next generation of control options for Rhizoctonia solani (AG8), the causal agent of Rhizoctonia root rot, is infurrow liquid injection. The efficacy of banding two new fungicides, Uniform® and EverGol® Prime, was evaluated as an alternative to seed treatments across three years of trials conducted in Western Australia (WA) by DAFWA and in South Australia (SA) by SARDI.
    • Uniform® applied either by liquid banding or coated fertiliser has been registered to control Rhizoctonia. Liquid banding treatments, including the split application of in-furrow and on the surface, produced greater and more consistent yield responses than Vibrance® seed treatment. Dual banding of Uniform® in-furrow 3-4 cm below the seed and on the surface behind the press wheel gave the most consistent yield and root health responses across seasons. Responses in barley were greater than wheat.
    • Yield responses achieved by banding EverGol® Prime in-furrow were not significantly different from EverGol® Prime seed treatments using comparable rates (gai). However, banding EverGol® Prime in-furrow combined with EverGol® Prime seed treatment resulted in better overall root health than in-furrow or seed only treatments.
  • Rotation with canola, or a clean fallow, greatly reduce the inoculum of Rhizoctonia in soils and will benefit the following cereal crop. Barley, on the other-hand, significantly increases inoculum.
  • Sub-seed furrow loosening is a well-established practice which reduces the effect of the disease.

Rhizoctonia and Crown Rot status of Western Australian paddocks can be managed with crop rotation (PDF 25kb)

By Roger Lawes (CSIRO), Martin Harries, Daniel Huberli, Greg Shea and Shahajahan Miyan (DAFWA). View Roger’s powerpoint presentation (PDF 146kb), Perth, February 2015.

  • A survey of farmers’ fields from 2010 to 2013 found little Rhizoctonia and Crown Rot across the WA Wheatbelt.
  • However, the data demonstrated that even with low levels of disease present, rotation with break crops can manage inoculum levels of Rhizoctonia and Crown Rot.
  • Inoculum levels are likely to build up when continous cereals are grown; in fertile soils; and in dry summers.
  • Pastures did not offer a break to the cereal.

Reduce losses from Crown Rot through variety choice and inter-row sowing (PDF 371kb)

By Shahajahan Miyan, Daniel Hüberli, Miriam Connor, Kris Gajda and Bill MacLeod (DAFWA). View Daniel’s powerpoint presentation (PDF 1.2Mb), Perth, February 2015.

  • In field trials, crown rot incidence was often lower and grain yield higher in the wheat variety Emu Rock compared with the variety Mace and the durum wheat variety Kalka.
  • An advantage (up to 11% reduction in crown rot infected main tillers) is gained from sowing “off-row” (between the previous season’s rows of wheat stubble) compared to sowing “on-row” (directly into the previous season’s wheat rows).

Northern

Impact of crop varieties on RLN multiplication

By Brendan Burton (Northern Grower Alliance). Presented at Goondiwindi, March 2015.

  • Know your enemy – soil test to determine whether Root Lesion Nematode (RLN) are an issue and which species are present.
  • Select wheat varieties with high tolerance ratings to minimise yield losses in RLN infected paddocks.
  • To manage RLN populations, it is important to increase the frequency of RLN resistant crops in the rotation.
  • Multiple resistant crops in a rotation will be necessary for long term management of RLN populations.
  • There are consistent varietal differences in Pt resistance within wheat and chickpea varieties.
  • Avoid crops or varieties that allow the build-up of large populations of RLN in infected paddocks.
  • Monitor the impact of your rotation

High crown rot risk – barley vs wheat

By Steven Simpfendorfer, Rick Graham and Guy McMullen (NSW DPI). Presented at Goondiwindi, March 2015.

  • In 57% of trial comparisons Commander barley provided a significant yield benefit (av. 0.95 t/ha) over the bread wheat variety EGA Gregory.
  • In 30% of trial comparisons the effect of choosing Commander or EGA Gregory was neutral.
  • In 13% of trial comparisons Commander resulted in a significant yield penalty (av. 0.48 t/ha) compared to growing EGA Gregory, likely due to stress occurring earlier in the season.
  • Barley and bread wheat varieties do vary in yield response in the presence of crown rot infection.
  • Barley is very susceptible to crown rot infection and will not reduce inoculum levels for subsequent crops.

Improving the accuracy of PreDicta B soil testing

By Steven Simpfendorfer (NSW DPI), Alan McKay and Shawn Rowe (SARDI). Presented at Goondiwindi, March 2015.

  • PreDicta B® is a good technique for identifying the level of risk for crown rot (and other soil-borne pathogens) prior to sowing within paddocks. However, this requires a dedicated sampling strategy and IS NOT a simple add on to a soil nutrition test.
  • Soil cores should be targeted at the previous winter cereal row if evident and RETAIN any stubble fragments.
  • Short pieces of stubble (two from each PreDicta B® soil sampling location) from previous winter cereal crops and/or grass weed residues can be added to the soil sample to enhance detection of the Fusarium spp. that cause crown rot.
  • ‘Spiking’ with stubble will reduce the likelihood of ‘failure to warn’ situations for crown rot but unfortunately will also increase the probability of false warnings.

Crown rot tolerance in new wheat cultivars is there enough to base varietal decisions on

By Rob Long (B&W Rural and Crown Analytical Services). Presented at Goondiwindi, March 2015.

  • In 7 trials over 3 years (2012-2014), recently released varieties demonstrated improved yield performance in the presence of crown rot relative to EGA Gregory, Sunguard (+17%), Suntop (+16%), LRPB Lancer (+15%), Spitfire (+12%).
  • Growers should consider alternatives to EGA Gregory unless they have confirmed their paddock has a LOW crown rot risk.
  • Crown rot tolerance, whilst important, should not necessarily be the most critical factor to choose a variety, nor should it be the first line of defence to combat the disease.
  • Growers/advisors should determine the level of crown rot risk for every paddock so they can choose the optimal variety to plant.
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