New developments in PreDicta B and management of rhizoctonia root rot

Shawn Rowe1, Marg Evans1, Paul Bogacki1, Sjaan Davey1, Alan McKay1,  Jack Desbiolles2, Gupta Vadakattu3, Steven Simpfendorfer4, Daniel Hüberli5, Miriam Connor5, Bill MacLeod5, Robert Battaglia6, Leanne Forsyth6, Trevor Klein6, Mike Clarke7, Geoff Robertson7 and Ray Correll8,

1South Australian Research and Development Institute (SARDI); 2University of South Australia; 3CSIRO; 4NSW DPI; 5DAFWA South Perth; 6Syngenta Australia; 7Bayer CropScience; 8RHO Environmetrics Pty Ltd.

ɸExtra technical comment by Protech Consulting Pty Ltd

GRDC project codes: DAS00137, DAS00122, DAS00123, DAS00125, DAN00175, CSP00150, DAW00174, DAW00229, and UWA00152

Take home messages

  • 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.

Background

Aims

To enhance value of PreDicta B and increase adoption by grain producers to minimise the yield losses from unexpected soil and stubble borne diseases.

Support development of new management practices and products to improve control of rhizoctonia.

PreDicta B

PreDicta B is a unique DNA based service developed to assist Australian grain producers identify which soilborne diseases posed a significant risk to the next crop, so that the cropping program can be adjusted before seeding to include strategies to minimise the risk.  The service now includes tests for the organisms that cause most of the main soilborne diseases, including cereal cyst nematode, take-all, rhizoctonia root rot, root lesion nematodes and crown rot.  DAS000137 has been funded by GRDC to increase the value of PreDicta B to growers. This includes expanding the range of tests for a broader range of organisms associated with soilborne diseases e.g. associated with Pythium root rot, common root rot; broadening the range of stubble borne diseases e.g. yellow spot and eyespot; expanding the range of tests for soilborne diseases of pulses and canola, and developing tests for indicators of soil health (DAS00111).  

In 2012, Steven Simpfendorfer, NSWDPI found that PreDicta B under estimated the risk of crown rot in 25% of samples.  The problem seemed to be due to soil samplers using the soil nutrition sampling protocol to collect samples i.e. coring was targeted midway between the rows of the previous crop and plant debris was avoided or removed.  This strategy underestimates the risk of stubble borne diseases.

Rhizoctonia root rot

Rhizoctonia root rot has been an ongoing problem in the low to medium rainfall areas especially on sandy soils and some areas in the high rainfall zone e.g. western slopes in southern NSW. In recent years GRDC has funded several projects, some in collaboration with SAGIT, which have greatly improved our understanding of rhizoctonia and supported development of new cropping practices to reduce the risk of yield loss.

This paper focuses on the results of two projects, DAS00122 and DAS00123, conducted in collaboration with industry (Syngenta and Bayer CropScience) to explore new fungicides and methods of application to improve options for control of rhizoctonia root rot. The trials were conducted across SA and WA from 2011 to 2013 by SARDI, UniSA and DAFWA.

Fungicide efficacy trials

All trial sites which were selected had a history of rhizoctonia root rot, followed a cereal and had medium to high Rhizoctonia DNA levels as measured by PreDicta B using soil samples collected in autumn.

Rhizoctonia root rot has a notoriously patchy distribution which makes detecting treatment differences difficult. To deal with the variability, plot length was increased to 20m (from often only 5m to 10m), the randomised block experimental design had six replicates and extra untreated plots were incorporated into the trial design. In SA the trials were sown by UniSA using a research plot seeder set up to deliver the fungicide treatments to the 3 RHS rows of each 6-row plot.  In WA, each 8-row wide treated plot was adjacent to an untreated plot.  Data were analysed by Dr Ray Correll of RHO Environmetrics.

Plots were sown in SA using narrow points and in WA using inverted T super seeder points, both cultivated to a depth of 10cm.Seeds were placed at 3cm depth under the press-wheel furrow surface.

In WA, Flexi-N +/- Uniform® or BYF14182 was liquid streamed to the bottom of the furrow in 2012 and 2013, while in 2011 a granular fertiliser was applied below the seed and Uniform® or BYF14182 were applied as a liquid stream.  The Uniform® treatments applied to the soil surface at the same volume per ha were applied as a liquid stream in a separate pass following the first pass application of fungicide below the seed during seeding.  The dual application treatments maintained the same chemical rate per ha but doubled the application volume per ha.

In SA, plots received either liquid NP fertiliser or a mix of granular DAP + liquid UAN fertilisers all banded at the base of the furrow (10cm below the soil surface) and in-furrow fungicide was co-located separately in water at 75-80L/ha volume. The Uniform® treatment applied to the soil surface at the same volume per ha was simultaneously applied as a 2cm wide band behind the press wheel during seeding and using a low volume narrow angle nozzle. The dual application treatments maintained the same chemical rate per ha but doubled the application volume per ha.

Evaluation of Uniform® and Vibrance®

Twenty-one field trials, 10 barley and 11 wheat, were established to evaluate Uniform® compared to Vibrance® seed treatment. Uniform® was applied at different rates and locations including a dual treatment of soil surface application behind the press wheel with in-furrow injection 3-4cm below the seed, an in-furrow injection below the seed only, and an in-furrow injection below the seed in combination with a seed treatment (Vibrance®). Summary of a META analysis of the combined data is presented in Table 3.  

Evaluation of EverGol® Prime seed treatment and BYF14182 in-furrow application

Nine trials were conducted across SA and WA to evaluate different methods of applying EverGol® Prime and BYF14182 to reduce yield loss caused by rhizoctonia root rot. Treatments included BYF14182 liquid stream applied in-furrow 3-4cm below the seed, or applied in-furrow 3-4cm below the seed combined with EverGol® Prime seed treatment, or EverGol® Prime seed treatment only (Table 4).

Results and discussion


From 2010 to 2012, 23% of the PreDicta B samples collected in the northern NSW focus paddock survey underestimated the risk of crown rot by at least two risk categories compared to plating assessment of incidence of infection in stubble collected from the same paddocks.  Previous research had shown a high correlation between PreDicta B results and crown rot.  It was suspected soil samplers had defaulted to using the soil nutrition sampling strategy. 

When 15 pieces of cereal or grass weed stubble (one piece by 15 locations), about 5-7cm long were added to PreDicta B samples, the assessment of crown rot risk increased by at least two risk categories in 27% of samples compared to similar PreDicta B samples where stubble was avoided (Table 1 and Table 2).

Table 1.  Comparison 2012 crown rot assessed by PreDicta B soil samples and plating stubble. 

PreDicta B

Crown rot risk

Crown rot risk assessed by plating (% incidence)

High ≥25

(n=87)

Medium 11-24%

(n=63)

Low 3-10%

(n=88)

Nil 0-2%

(n=69)

High (n =45)

28$

8

8

1

Medium (n = 37)

17

13

6

1

Low (n = 46)

12

15

9

10

BDL* (n = 179)

30

27

65

57

*BDL= Below detection limit; $= Number of samples in the same risk category

Table 2.  Impact of adding stubble to PreDicta B samples on risk assessment of crown rot.

Stubble avoided

Stubble added

Risk

High

(n=71)

Medium

(n=20)

Low

(n=54)

BDL

(n=122)

High (n = 6)

6$

0

0

0

Medium (n = 6)

6

0

0

0

Low (n = 80)

44

8

22

6

BDL (n = 175)

15

12

32

116


Rhizoctonia fungicide efficacy trials

Tables 3 and 4 summarise the yield responses associated with each fungicide treatment using individual site analyses and Meta analysis of the combined data for all sites. A direct comparison between EverGol® Prime and Vibrance® cannot be made as they were evaluated in separate experiments.

Uniform® and Vibrance®

Analysis of the pooled Uniform® and Vibrance® data from the wheat and barley trials showed that the treatment responses were highly correlated (r = 0.95) and that wheat yield increases were typically 65% of those in barley.  

Significant yield increases were obtained for all treatments in barley and wheat (Table 3).  The Uniform® liquid banding treatments produced significantly greater and more frequent yield responses than Vibrance® seed treatment alone. The best results were obtained by the dual application of Uniform® at 200mL/ha in-furrow and on the surface (total 400mL/ha); on average this increased yield of barley by 0.46 ± 0.22t/ha and wheat 0.32 ± 0.11t/ha.   This treatment was not statistically different from the dual application of Uniform® at 150mL/ha each location (total 300mL/ha).   The profitability of these treatments can be tested when the price of Uniform® is released.

Table 3. Summary of barley and wheat yield responses for treatments with Vibrance® (Vib seed treatment; mL/100kg) and Uniform® (Uni) liquid banded in-furrow (IF) and on the surface (Sur) at the specified rates (mL/ha). 

 Crop

Treatment

Years

No. trials where yield response significant P>0.05 §

Trials with +ve yield responses

Yield

Untreated (t/ha)

Treated (t/ha)

Net (t/ha)

Barley

Vib seed 360mL/100kg seed

3

1 of 10

6 of 10

2.34

2.37

0.02

Vib seed 360 + Uni IF 200mL/ha

3

5 of 10

9 of 10

2.34

2.53

0.18*

Uni IF 300mL/ha

3

5 of 10

8 of 10

2.34

2.55

0.21*

Uni IF 400mL/ha

2

5 of 6

5 of 6

2.65

2.95

0.30*

Uni Sur 150 + Uni IF 150

2

3 of 6

5 of 6

2.65

2.93

0.28*

Uni Sur 200 + Uni IF 200

1

2 of 3

3 of 3

3.03

3.48

0.46*

Wheat

Vib seed

3

3 of 11

10 of 11

2.18

2.25

0.07

Vib seed + Uni IF 200

3

6 of 11

9 of 11

2.18

2.31

0.13*

Uni IF 300

3

8 of 11

9 of 11

2.18

2.33

0.15*

Uni IF 400

2

4 of 6

6 of 6

2.22

2.39

0.17*

Uni Sur 150 + Uni IF 150

3

6 of 7

7 of 7

2.07

2.30

0.22*

Uni Sur 200 + Uni IF 200

1

3 of 3

3 of 3

2.79

3.11

0.32*

§Yield increase significantly greater than untreated based on individual site analyses.

* Net yield increases significant at p<0.05 based on Meta analysis of combined data from all sites.

Uniform®a has efficacy on smuts in barley and wheat, and yellow spot in wheat but these aspects were not part of this study (ɸ a Not registered for smuts in barley or wheat and registered for suppression of yellow spot in wheat)

Table 4.  Summary of barley yield responses for EverGol® Prime (EP) used as a seed treatment (mL/100kg seed) and BYF14182 in-furrow (IF). IF rates are not specified as product is not currently registered.

Treatment

Years

No. trials where yield response significant P>0.05§   

Trials with +ve yield responses

Yield

Untreated (t/ha)

Treated (t/ha)

Net (t/ha)

EP seed 40mL/100kg seed

1

0 of 3

2 of 3

2.12

2.17

0.04

EP seed 80mL/100kg seed

3

2 of 6

6 of 6

2.37

2.51

0.14*

BYF14182 IF rate 1

2

0 of 4

4 of 4

2.25

2.32

0.07

BYF14182 IF rate 2

3

1 of 6

3 of 6

2.37

2.46

0.09

BYF14182 IF rate 3

1

1 of 2

1 of 2

2.62

2.81

0.20*

BYF14182 IF rate 4

2

1 of 4

3 of 4

2.25

2.34

0.08

EP seed 40 ml/100 kg seed + BYF14182 IF rate 1

1

1 of 2

1 of 2

2.62

2.74

0.13

§Yield increase significantly greater than untreated based on individual site analyses.

* Net yield increases significant at p<0.05 based on Meta analysis of combined data from all sites.

EverGol® Prime and BYF14182

EverGol® Prime and BYF14182 treatments produced positive yield responses in at least some trials, but not all responses were significant (Table 4).  The meta-analysis of all the EverGol® Prime and BYF14182 trial data showed the seed treatment 80mL/100kg produced a significant net yield gain of 0.140 ± 0.055t/ha.  Responses across all treatments averaged 0.11t/ha or 6%.  There was no yield advantage associated with liquid banding over the seed treatment using comparable rates of product.  The best yield response, 0.195 ± 0.096t/ha was obtained when BYF14182 was liquid banded in-furrow at rate 3; the response was statistically significant as this treatment but was evaluated in only two trials in one year.  The profitability can be tested when BYF14182 is registered.

Summary of management practices that reduce Rhizoctonia disease impacts

  • Grass free canola, pulses and pastures provide useful reduction in Rhizoctonia levels for the following crop.
  • Frequent summer rainfall combined with good summer weed control.
  • Autumn “green bridge” controlled.
  • Knife point soil openers reduce risk of Rhizoctonia compared to discs.
  • Sow at earliest optimum time and till below seed to facilitate root growth down soil profile.
  • Consider increasing seeding rate to reduce impact of lost tillers due to Rhizoctonia damage to crown roots.
  • Band N below the seed and avoid incorporating stubble to minimise N deficiency during crop establishment.
  • Address in-crop nutrient/trace element deficiencies with foliar application.

Conclusions

PreDicta B

  • Crown rot is likely to be the main soil/stubble borne disease risk in 2015.  Check SARDI website for link to new PreDicta B site which should be launched in March. This will include latest information and current and previous maps of PreDicta B results.
  • Target sampling along the rows of the last cereal crop. 
  • Collect three 1x10cm cores (AccuCore) from 15 different locations within the target sampling area/paddock.
  • Add stubble (if present) – at each of the 15 sampling locations, select one piece of  stubble about 5-7cm long from the base of a cereal plant or grassy weed and add the lower portion to the sample bag.

Rhizoctonia

  • Liquid banding of fungicides provides greater flexibility for growers to use fungicides for control of R. solani.
  • Uniform® has been registered to control Rhizoctonia and has been shown to significantly reduce yield losses caused by rhizoctonia root rot when applied as a liquid band either at dual locations (on soil surface plus below the seed), in-furrow only, or in furrow combined with a seed treatment (Note Uniform® is not registered as a seed treatment).
  • Efficacy of fungicides to control rhizoctonia seems to vary between seasons. Further work is required to identify the seasons in which yield responses are greatest. 
  • Fungicides should be used as part of an integrated management package to control rhizoctonia root rot.  When sowing to wheat or another cereal in a paddock with a high rhizoctonia risk, sow early, cultivate below the seed and apply sufficient nitrogen (N) nutrition at seeding.
  • Grass free canola, pulse or pasture will reduce risk of rhizoctonia but levels will increase by the end of the following cereal crop.  

Further reading

GRDC Factsheet March 2012 (will be updated in 2015)

Consultants accredited to deliver PreDicta B can download the latest root disease manual

Acknowledgments

GRDC, SAGIT, Syngenta and Bayer CropScience for funding the research. SARDI New Crop Agronomy group for managing weed control and harvesting the SA trials. DAFWA Geraldton, Katanning, Northam and Wongan Hills Research Support Units for seeding and harvesting trials. All the growers who kindly allowed SARDI and DAFWA to conduct the trials on their land during 2009 to 2014. Liquid Systems SA and Topcon Precision Agriculture for directly supporting the SA research component.

Contact details

Alan McKay
Alan.Mckay@sa.gov.au

GRDC Project code: DAS00137, DAS00122, DAS00123, DAS00125, DAN00175, CSP00150, DAW00174, DAW00229, and UWA00152