Rhizoctonia control improved by liquid banding of fungicides

Paul Bogacki¹, Jack Desbiolles², Ray Correll³, Daniel Hüberli⁴, William Macleod⁴ and Alan McKay¹,

¹South Australian Research and Development Institute, ²University of South Australia, ³Rho Environmetrics Pty Ltd, ⁴Department of Agriculture and Food, Western Australia.

GRDC project code: DAS00122, DAS00123, and DAS00125

Keywords: Rhizoctonia, fungicides, liquid banding.

Take home messages

• Results of field trials have shown that banding the fungicides Uniform® and EverGol® Prime can significantly increase grain yield of wheat and barley in Rhizoctonia affected paddocks.
• Treatments incorporating a “split” application of fungicide with half the rate banded on the surface behind the press wheel and half banded approximately 3.5 cm below the seed produced the most consistent yield responses.
• The APVMA is currently reviewing submissions from Syngenta and Bayer CropScience to enable banding of Uniform® and EverGol® Prime to control Rhizoctonia in wheat and barley; if approved, registration should be granted by 2015.  
• Permits have been secured for large scale paddock evaluation of these products in 2014; look out for local field days conducted by Syngenta and Bayer CropScience. 
• Use of fungicides will reduce Rhizoctonia patch incidence and severity but not eliminate patches all together; fungicides will still need to be used as part of an integrated management program.  

Background

Rhizoctonia bare patch caused by the fungus Rhizoctonia solani AG8 continues to be a devastating disease of wheat and barley in Australia, causing reductions in grain yield which can cost the industry up to $77 million per annum (Murray and Brennan, 2009, 2010). With the recent registration of seed treatment fungicides such as Vibrance^TM and EverGol® Prime, growers now have better options to control Rhizoctonia by chemical means. In SARDI and DAFWA field trials these new seed treatments increased wheat and barley yields by 5 per cent on average.

Based on what we know about the distribution of Rhizoctonia in the top ten cm of soil and the damage it can cause to both crown and seminal roots, trials were conducted by SARDI and DAFWA from 2011-2013 to evaluate whether liquid banding of fungicides could provide an additional level of control and to generate efficacy data for label registration. Banding fungicide approximately 3.5 cm below the seed and/or on the soil surface behind the press wheel was anticipated to provide better protection to the crown and seminal roots, respectively. This paper summarises the yield responses from most of those trials. 

Methodology

Twenty-two fungicide efficacy trials, sown to either barley or wheat, were established in SA and WA from 2011-2013. Trial sites were selected based on Rhizoctonia bare-patching in the previous year’s cereal crop combined with results from PreDicta B soil DNA tests to identify medium to high risk paddocks; all trials utilised native R. solani inoculum present in the paddock.

The trials had a randomised block design with six replicate plots (20 m x 1.8 m) per treatment, which included liquid banding of fungicides Uniform® (Syngenta) and EverGol® Prime (Bayer CropScience) on the soil surface and in-furrow 3.5 cm below the seed, in-furrow below the seed only, or in-furrow below the seed combined with a seed treatment (either Vibrance^TM or EverGol® Prime). Different rates of product were also tested. In SA, individual plots were split into treated and untreated halves whereas in WA each treated plot was adjacent to an untreated plot. All treatments were compared with untreated control plots.

All plots were sown using knife points. In SA, plots received either liquid or granular + liquid UAN fertilisers in different years and fungicide was applied separately in water at 75-80 L/ha. The surface application of fungicide behind the press wheel was achieved using a low volume narrow angle nozzle set to spray along its narrow side creating a band approx. 2 cm wide. In WA, plots were injected with Flexi-N +/- fungicide below the seed in 2012 and 2013, while a granular fertiliser was applied below the seed in 2011 and fungicide was applied in water. The surface band treatment was applied as a trickle in a separate pass following the first pass application of fungicide as a trickle below the seed using GPS controlled auto-steer.

Results and discussion

Only results obtained with Uniform® are presented to avoid supporting off-label use of EverGol® Prime (which is already registered and available as a seed treatment).

Yield responses for six main treatments are presented in Tables 1 and 2 for wheat and barley, respectively. Note that some treatments were evaluated in recent years only. The results are presented as net yield increases (t/ha) for each treatment, with the site untreated yields (t/ha) and pre-sowing R. solani levels included to characterise each site.

Table 1. Summary of net wheat yield responses (t/ha) in Rhizoctonia fungicide application trials with Uniform® and Vibrance^TM.

* Significant (P < 0.05) or ** Significant (P < 0.001), compared to untreated plots

Vib = Vibrance^TM seed treatment applied at 360 mL/100 kg seed, IF = Uniform® applied in in-furrow (3-4 cm below seed), Sur = Uniform® applied on furrow surface

Table 2. Summary of net barley yield responses (t/ha) in Rhizoctonia fungicide application trials with Uniform® and Vibrance^TM.

* Significant (P < 0.05) or ** Significant (P < 0.001), compared to untreated plots

Note: because Rhizoctonia field trials are inherently variable, it was difficult to detect statistically significant yield responses less than ten per cent and sometimes greater. 

The treatments producing the most consistent yield responses were those incorporating “split” application of Uniform® applied on the soil surface behind the press wheel and in-furrow 3.5 cm below the seed. In wheat, significant yield responses of 0.11 to 0.39 t/ha (6 of 7 trials) were found at the medium rate (rate 2) and 0.20 to 0.53 t/ha (4 of 4 trials) at the high rate (rate 3). In barley, significant responses of 0.25 to 0.69 t/ha (3 of 6 trials) were observed at the medium rate and 0.37 to 0.87 t/ha (2 of 3 trials) at the high rate.

Application of Uniform® in-furrow only produced significant yield increases in wheat of 0.12 to 0.33 t/ha (7 of 11 trials) at the medium rate and 0.08 to 0.42 t/ha (5 of 7 trials) at the high rate. In barley, net yield responses of 0.25 to 0.69 t/ha (5 of 10 trials) at the medium rate and 0.26 to 0.53 t/ha (5 of 6 trials) at the high rate were found.

Banding below the seed at the low rate in combination with Vibrance^TM seed treatment increased yield significantly by 0.09 to 0.47 t/ha in wheat (6 of 11 trials) and 0.17 to 0.62 t/ha in barley (4 of 10 trials). Seed treatment alone increased yield significantly in 3 of 11 wheat trials and 1 of 10 barley trials.

Conclusions

Method of application does matter.  Liquid banding of fungicides either in-furrow only or as a “split” application with half the rate banded below the seed and half on the soil surface has better efficacy than the seed treatments. There were more significant yield responses with the banding treatments and the magnitudes of the responses were also generally better. The “split” application consistently gave the biggest responses.

Acknowledgements

Funds for research trials were provided by GRDC, SAGIT, Syngenta and Bayer CropScience. The in-kind support from Liquid Systems SA and TopCon Precision Agriculture in supplying liquid metering and dispensing Spiker technology and associated X20 liquid rate controller, respectively, is greatly appreciated.

Contact details

Dr. Paul Bogacki

SARDI, Plant and Soil Health

8303 9587

paul.bogacki@sa.gov.au