Management of disease complexes in the Southern Victorian Mallee cereals
Author: Thomas Jones and Yolanda Plowman (Birchip Cropping Group) | Date: 06 Feb 2024
Take home messages
- Variety choice is important for disease management.
- Economical and premium fungicide options performed similarly in many cases.
- Spot form and net blotch were common diseases in the southern Mallee barley site.
- Septoria tritici blotch, leaf and stripe rust were observed in the southern Mallee wheat site.
- Disease resistance of variety plays an important role in disease management in-season.
Background
The Mallee region experiences substantial fluctuations in seasonal conditions, with varying rainfall and patterns in recent years. This variability poses challenges in predicting the risk of disease and timing of application to produce economic returns for growers from fungicide use to manage disease. Given the nature of inconsistencies in economic returns for fungicide use in the Mallee environment, this project was established to support growers in making real-time decisions for disease control and maximise benefits from fungicide use. The objective of this project is to showcase diverse management strategies for disease complexes and identify optimal economic strategies that suit different crops grown in the Mallee region. This involves conducting plot trials at multiple locations, emphasising various fungicide management approaches in wheat, barley, and lentils. The trials are designed to encourage facilitated discussions and peer-to-peer learning regarding critical disease management decisions.
Method
Site establishment
In 2023, the Birchip Cropping Group (BCG) established five small-plot research trials across two locations in regional Victoria, the Mallee, located in Kinnabulla, 20km northwest of Birchip, and the North Central region, 13km south of Pyramid Hill. Data from the two Pyramid Hill trials (barley and wheat) have been omitted from this report, as the trials experienced heavy pressure from kangaroo grazing throughout the year. The three trials at the Kinnabulla site were sown to wheat, barley, and lentil, with different disease management strategies applied (Table 2). Data collected from the lentil trial showed that the disease load was lower than expected, and therefore this trial has been omitted from this report. All trials were established as randomised complete block design with four replications. The sites experienced timely early season rainfall with 57.4mm in June, resulting in good trial establishment as well as early season disease development. During the growing season, the trial received 187mm of rain. The rainfall received during the growing season was classified as decile 3, however, there was sufficient soil moisture due to higher-than-average rainfall (decile 10) in 2022.
Crop varieties and disease susceptibility
Three different varieties within each crop type were selected with varying disease susceptibility ratings (Table 1).
Table 1: Wheat and barley variety disease ratings1 as follows, moderately resistant (MR), susceptible (S), moderately susceptible (MS), very susceptible (VS).
Disease | Variety | ||
|---|---|---|---|
Wheat | |||
Scepter | Hammer CL Plus | LRPB Matador | |
Septoria tritici blotch | S | MS to S | S (P)2 |
Leaf rust | MS to S | S | S (P) |
Stripe rust | MS to S | MS | MS |
Barley | |||
Leabrook | Maximus CL | RGT Planet | |
Spot form net blotch | MR | MS | S to VS |
Leaf scald | S to VS | S | S |
1 Disease ratings were sourced from the 2024 NVT Disease ratings.
2 Provisional rating.
Treatments
Table 2: Fungicide management spray treatments and application timings in wheat and barley. Treatments were chosen to illustrate a variety of different fungicide options to evaluate differences between economical and premium fungicide application strategies.
Treatment | Pricing | Method/timing^ | Rate | |
|---|---|---|---|---|
i) | Control | No fungicide | ||
ii) | Flutriafol | 400mL/100kg | ||
iii) | 250 g/L Propiconazole and 40 g/L Benzovindifupyr | GS31 | 500mL/ha | |
iv) | Flutriafol and 125 g/L Epoxiconazole | Economical | GS31 | 400mL/100kg |
v) | Flutriafol, 250 g/L Propiconazole and 40 g/L Benzovindifupyr | Premium | GS31 | 400mL/100kg 500mL/ha |
vi) | 250 g/L Propiconazole and 40 g/L Benzovindifupyr | GS39 | 500mL/ha | |
vii) | Flutriafol, 125 g/L Epoxiconazole 200 g/L Azoxystrobin and 80 g/L cyproconazole | Economical | GS31 GS39 | 400mL/100kg 500mL/ha 800mL/ha |
viii) | Flutriafol, 250 g/L Propiconazole and 40 g/L Benzovindifupyr 150 g/L Prothioconazole and 75 g/L Bixafen | Premium | GS31 GS39 | 400mL/100kg 500mL/ha 500mL/ha |
^Growth stage according to Zadoks scale, GS31 = stem elongation, GS39 = flag leaf emergence.
Results and discussion
Wheat
Variety was a primary driver in differentiating disease prevalence at growth stages GS31 and two weeks post-GS39, p <0.001 and p=0.036, respectively (Table 3). Septoria tritici blotch (STB) was detected on lower leaves early in the season (GS31). At GS39, STB had migrated into the upper canopy in all varieties. The presence of rust was also noted at this growth stage in some untreated Hammer CL Plus plots. Two weeks following the GS39 treatment application, rust had formed hotspots in the trial, with rust appearing in most plots.
Table 3: General disease scores in wheat noted at four time points throughout the season.
Variety | Treatment | GS31 | 2 weeks post GS31 trt | GS39 | 2 weeks post GS39 trt |
|---|---|---|---|---|---|
Hammer CL Plus | Control | 3 | 3 | 5 | 5 |
ii) | 2 | 3 | 4 | 4 | |
iii) | 3 | 3 | 3 | 4 | |
iv) | 2 | 3 | 4 | 4 | |
v) | 2 | 3 | 4 | 4 | |
vi) | 2 | 4 | 5 | 4 | |
vii) | 2 | 3 | 3 | 4 | |
viii) | 2 | 3 | 3 | 3 | |
LRPB Matador | Control | 2 | 3 | 4 | 5 |
ii) | 2 | 3 | 3 | 3 | |
iii) | 2 | 3 | 3 | 3 | |
iv) | 2 | 3 | 3 | 3 | |
v) | 2 | 3 | 3 | 3 | |
vi) | 3 | 3 | 4 | 3 | |
vii) | 2 | 3 | 4 | 2 | |
viii) | 2 | 3 | 3 | 3 | |
Scepter | Control | 3 | 3 | 6 | 7 |
ii) | 3 | 3 | 3 | 3 | |
iii) | 3 | 3 | 4 | 4 | |
iv) | 3 | 3 | 3 | 3 | |
v) | 3 | 3 | 4 | 3 | |
vi) | 3 | 3 | 5 | 4 | |
vii) | 3 | 3 | 3 | 4 | |
viii) | 3 | 3 | 3 | 2 | |
Sig. Diff. | |||||
Variety | <.001 | NS | NS | 0.036 | |
Treatment | NS | NS | 0.001 | <.001 | |
Variety x Treatment | NS | NS | NS | NS | |
Lsd (p=0.05) | |||||
Variety | 0.1537 | NS | NS | 0.527 | |
Treatment | NS | NS | 0.961 | 0.86 | |
Variety x Treatment | NS | NS | NS | NS | |
CV (%) | |||||
Variety | 2.2 | NS | NS | 5.3 | |
Treatment | NS | NS | 5.1 | NS | |
Variety x Treatment | NS | NS | NS | 5.3 | |
Plots were scored from 1–9 (9 = whole plot diseased). Replicate data for each group are summarised as the mean, based on four replicates unless otherwise stated. Scores denote observations of general signs of disease (lesions).
Both variety and treatment imposed statistically significant effects on grain yield (t/ha), p=0.008 and p=0.005, respectively (Table 4). Between the untreated controls, LRPB Matador was the highest yielding variety, and Scepter the lowest, illustrating the impact of disease, as shown in Table 3. Within varieties, Scepter was the most responsive to disease control, with all but one treatment (iii) showing a significantly higher yield compared with the control. Double spray applications (GS31 and GS39) resulted in the highest yield for Scepter (treatments vii and viii), with little difference between the economical and premium products. The partial gross margin (PGM) for treatment vii (GS31 and GS39 economical) showed a slightly higher return on investment (ROI), but the highest PGM for this variety was achieved by treatment vi, which was one application of propiconazole and benzovindifupyr at GS31.
Differences in yield between treatments were observed to a lesser degree for Hammer CL Plus, and less again for LRPB Matador. A common trend across both varieties was the high yields achieved for treatment iii (one application of propiconazole and benzovindifupyr at GS39) versus the premium version of this treatment (v) which included Flutriafol. Treatment iii across both varieties showed high yields, and the highest PGM.
Table 4: Average yield (t/ha) and partial gross margin (PGM) of wheat varieties and treatments.
Variety | Control | ii | iii | iv | v | vi | vii | viii | |
|---|---|---|---|---|---|---|---|---|---|
Hammer CL Plus | Yield (t/ha) | 4.50ef | 4.95b-e | 5.27a-d | 4.94b-e | 4.62d-f | 4.68d-f | 5.24a-e | 5.31a-d |
PGM($/ha)A | $1598 | $1739 | $1841 | $1707 | $1593 | $1630 | $1778 | $1798 | |
LRPB Matador | Yield (t/ha) | 4.89b-e | 4.94b-e | 5.80a | 5.17a-e | 5.46a-c | 5.47a-c | 5.61ab | 5.39a-d |
PGM($/ha)A | $1736 | $1738 | $2028 | $1787 | $1890 | $1910 | $1911 | $1824 | |
Scepter | Yield (t/ha) | 4.05f | 5.14a-e | 4.74c-f | 5.09a-e | 5.08a-e | 5.23a-e | 5.35a-d | 5.25a-e |
PGM($/ha)A | $1437 | $1808 | $1650 | $1759 | $1757 | $1824 | $1817 | $1775 | |
Sig. Diff. | |||||||||
Treatment | 0.005 | ||||||||
Variety | 0.008 | ||||||||
Treatment x variety | NS | ||||||||
Lsd (p=0.05) | |||||||||
Treatment | 0.4425 | ||||||||
Variety | 0.271 | ||||||||
Treatment x variety | NS | ||||||||
CV (%) | 2.2 | ||||||||
Replicate data for each group are summarised as the mean. The shading denotes significant differences for treatments compared to the control of respective variety.
A Partial gross margin of each treatment was calculated using the yields incorporated in the table, average price of APW $355 at three local receival sites (correct as of 3 January 2024) minus the flutriafol and fungicide prices and an application cost of $10 per spray.
An interesting finding was the lack of significant differences between economical and premium products, regardless of variety or spray application. However, PGM analysis showed in some instances that for plots with relatively similar yields, the return on investment was higher for the treatment using economic products, for example treatments iv (economic) and v (premium) in Hammer CL Plus, and treatments vii (economic) and viii (premium) in LRPB Matador and Scepter. This was not always the case, however, for example treatments iv (economic) and v (premium) in LRPB Matador and Scepter where the opposite trend is observed.
Barley
As observed for the wheat, barley establishment was aided by timely rain and soil moisture, and this was also likely to increase disease load. Spot form net blotch (SFNB) was detected in every barley trial plot. RGT Planet suffered substantially higher damage from SFNB than other varieties (Table 5), which is unsurprising as this variety is considered more susceptible to this disease than Maximus CL and Leabrook . At the time of the GS39 spray application net form net blotch (NFNB) was the main disease present in RGT Planet plots. Two weeks post-GS39 treatment application, NFNB had spread throughout the trial, however it was prevalent mainly in RGT Planet plots. At the same time point, leaf scald hotspots were beginning to appear within Maximus CL plots.
Table 5: General disease scores in barley noted at four time points throughout the seasons.
Variety | Treatment No. | GS31 | 2 weeks post GS31 trt | GS39 | 2 weeks post trt |
|---|---|---|---|---|---|
Leabrook | Control | 3 | 3 | 2 | 4^ |
ii) | 2 | 3 | 2 | * | |
iii) | 2 | 3 | 2 | 3 | |
iv) | 2 | 2 | 2 | 3 | |
v) | 2 | 2 | 2 | 3 | |
vi) | 2 | 3 | 2 | 3 | |
vii) | 2 | 3 | 2 | 3 | |
viii) | 2 | 3 | 2 | * | |
Maximus CL | Control | 3 | 3 | 3 | 2 |
ii) | 2 | 3 | 3 | * | |
iii) | 3 | 2 | 2 | 2 | |
iv) | 2 | 2 | 2 | 2 | |
v) | 3 | 2 | 2 | * | |
vi) | 3 | 3 | 3 | * | |
vii) | 2 | 3 | 3 | 3 | |
viii) | 3 | 3 | 3 | 3 | |
RGT Planet | Control | 4 | 5 | 5 | 6 |
ii) | 4 | 5 | 5 | 5 | |
iii) | 4 | 4 | 5 | * | |
iv) | 4 | 4 | 5 | 5 | |
v) | 5 | 5 | 5 | 5 | |
vi) | 4 | 5 | 5 | * | |
vii) | 5 | 4 | 5 | 4 | |
viii) | 4 | 5 | 5 | 4 | |
Sig. Diff. Variety Treatment Variety x Treatment Lsd (p=0.05) Variety Treatment Variety x Treatment CV (%) | NS NS NS NS NS NS NS | NS NS NS NS NS NS NS | NS NS NS NS NS NS NS | 0.007 <.001 0.003 0.2749 0.4489 0.7775 31.6 | |
Plots were scored from 1–9 (9 = whole plot diseased). Replicate data for each group are summarised, based on four replicates unless otherwise stated. Scores denote observations of general signs of disease present including evidence (lesions).
*Denotes missing values.
^Denotes one replicate of data.
Both treatment and variety imposed significant effects on the yield (t/ha) (p=0.041) and variety (p<0.001) for yield (t/ha). In the control plots, the mean yield in Maximus CL was significantly higher than the mean yields recorded for Leabrook and RGT Planet (Table 6). It is possible that the difference in yield between Maximus CL and the other varieties is due to slightly lower disease loads for this variety later in the season, as shown in Table 5. Given that Leabrook is the more resistant variety to SFNB, this may indicate that the environmental conditions in this trial favoured Maximus CL. Unlike the wheat trial, there were no varieties that responded strongly to treatments across the board, and for RGT Planet, no disease management treatment resulted in significantly different yields compared to the control.
Within the RGT Planet variety data, no significant differences were detected between treatments, including the control. Nevertheless, the highest yield was obtained by treatment viii, the complete treatment strategy (two sprays with premium products) however, this did not translate to return on investment, as shown by the PGM; the highest PGM for RGT Planet was for the control treatment. The opposite was true for Leabrook and Maximus CL; the highest return on investment occurred for plots that where the yields were significantly higher than the respective controls for each variety. These findings suggest a strong influence of variety choice and disease management strategies on each other.
Table 6: Average yield (t/ha) and partial gross margin (PGM) of barley varieties and treatments.
Variety | Control | ii | iii | iv | v | vi | vii | viii | |
|---|---|---|---|---|---|---|---|---|---|
Leabrook | Yield (t/ha) | 4.31f-j | 4.24 f-j | 4.91b-d | 4.48d-h | 4.50d-h | 4.64c-g | 4.43e-i | 4.49d-h |
PGM($/ha) A | $1,275 | $1,238 | $1,421 | $1,279 | $1,283 | $1,342 | $1,228 | $1,239 | |
Maximus CL | Yield (t/ha) | 4.84c-e | 4.87b-e | 5.10a-c | 5.34ab | 4.73c-f | 4.80c-e | 5.53a | 5.48a |
PGM($/ha) A | $1,431 | $1,426 | $1,477 | $1,532 | $1,349 | $1,390 | $1,553 | $1,534 | |
RGT Planet | Yield (t/ha) | 3.98ij | 3.85j | 3.86j | 3.91j | 4.09h-j | 3.86 j | 4.07 h-j | 4.22g-j |
PGM($/ha) A | $1,177 | $1,124 | $1,110 | $1,111 | $1,162 | $1,110 | $1,124 | $1,160 | |
Sig. Diff. | |||||||||
Treatment | 0.041 | ||||||||
Variety | <.001 | ||||||||
Treatment x Variety | NS | ||||||||
LSD (p=0.05) | |||||||||
Treatment | 0.2806 | ||||||||
Variety | 0.1718 | ||||||||
Treatment x Variety | NS | ||||||||
CV (%) | 0.3 | ||||||||
A Partial gross margin of each treatment was calculated using the yields incorporated in the table, average price of BAR1 $296 at three local receival sites (correct as of 3 January 2024) minus the flutriafol and fungicide prices and an application cost of $10 per spray. The shading denotes significant differences for treatments compared to the control of respective variety.
Only one instance of significant difference between economic and premium products was detected; this was for treatments iv (economic) and v (premium) for Maximus CL, where the economic treatment sprayed only at GS31 yielded higher than the premium treatment sprayed at GS31. As a result of the higher yield and lower input cost, the PGM showed a higher ROI for the economic option. Nevertheless, the yield for this treatment was lower than that for both the economical and premium double-spray option for this variety, indicating that for this variety, the double-spray choice was the ideal strategy, regardless of product choice, as the PGM showed a comparable ROI between the two double-spray strategies.
Conclusion
Interim findings of this project suggest that there are complex interactions between variety choice and disease management strategy. For wheat, Scepter was more receptive to fungicide treatment compared to LRPB Matador and Hammer CL Plus. Despite this, no substantial difference in yield was detected between economic and premium products for this variety, and in this case the choice may be driven more by ROI, rather than yield alone. Similar observations were made for barley, however RGT Planet did not exhibit receptivity to any treatment when compared to the control. Like the wheat trial, only one product comparison showed a significant difference in yield between the single-spray economic and premium treatments at GS31. It is hypothesised these effects may vary season to season, and that variety susceptibility plays a significant role. BCG will continue this work in 2024 to build on the work presented here.
Acknowledgements
The research undertaken as part of this project is made possible by the significant contributions of growers through both trial cooperation and the support of the GRDC, the authors would like to thank them for their continued support. BCG would also like to acknowledge former BCG employee Genevieve Clarke for designing the trial, Dr Hari Dadu from Agriculture Victoria for his advice and assistance throughout the year, and Rik Maatman from Nutrien Ag Birchip for providing indicative prices for products used in this trial.
Useful resources
Contact details
Yolanda Plowman
73 Cumming Avenue, Birchip VIC 3487
0447 755 312
Yolanda.plowman@bcg.org.au
@YolandaPlowman
Thomas Jones
73 Cumming Avenue, Birchip VIC 3487
0458 409 205
Thomas.jones@bcg.org.au
GRDC Project Code: BWD2303-002RTX,
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