In many ways, our growers should not be relying so heavily on spraying providing all the solutions. For example, if you have signs of disease at the tillering stage, it is something of a Catch-22: you need to do the maths to see if the cost of another spray at this stage justifies the outcome.
IF you think farmers have to make some tough decisions about which crops are going into their paddocks and how to best ensure a good harvest comes out the other end of the season, spare a thought for the researchers who have to provide the data that are essential to many of these decisions.
Because, in this digital era there is more and more information ‘out there’ and wading through it is critical to optimum performance for growers.
Birchip Cropping Group research senior manager Dr Yolanda Plowman recently completed a series of regional presentations to farmers and advisers about disease management in Mallee cereals.
Yolanda says despite all the advice being distributed, she remains convinced the industry in general values these hands-on opportunities and the timely reminders.
Filtering the data for such presentations is a not-insignificant challenge for the Dr Plowmans of the world.
She says they need to provide participants with key take-home messages, which in the current round of workshops reporting on trials have included:
* Variety choice is important for disease management.
* Economical and premium fungicide options perform 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.
“The thing is, Australia is actually in a pretty good position in terms of weed management in cropping because we have good chemistry here,” she says.
“Which is why, in many ways, our growers should not be relying so heavily on spraying providing all the solutions.
“For example, if you have signs of disease at the tillering stage, it is something of a Catch-22: you need to do the maths to see if the cost of another spray at this stage justifies the outcome.”
Yolanda says the Mallee region experiences substantial fluctuations in seasonal conditions, with varying rainfall patterns in recent years.
She says 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, BCG projects have been established to support growers in making real-time decisions for disease control and to maximise benefits from fungicide use.
“The objective of the project we have just been delivering to growers and advisers is to showcase diverse management strategies for disease complexes and identify optimal economic strategies which suit different crops grown in the Mallee region,” Yolanda says.
“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 with an aim of showcasing diverse management strategies for disease complexes and identifying optimal economic strategies that suits different crops grown in the Mallee.”
Yolanda stresses that despite all ongoing research, so many actions, and reactions, in farming are seasonally dependent – for example, if a farmer had an abnormally wet season, they would make the obvious adjustments to their spraying program.
She says that’s where farmers and farm advisers need to nuance the season and the products they are using to achieve the best possible outcome, particularly with the volume of available material coming in to growers growing exponentially and always there on the phones in their hands or the tablets in their tractor cabins.
“The variables are endless.” Yolanda says.
“In some instances you are dealing with wheat on wheat, others have a single break, or double, in varying soil and climatic conditions, so every decision made needs to reflect that.
“One of the things people would also do well to keep high on their list of priorities are the AFREN principles.”
The GRDC-funded Australian Fungicide Resistance Extension Network brings together regional plant pathologists, fungicide resistance experts, and communications and extension specialists to develop and deliver fungicide-resistance resources to growers and advisers across the country.
Fungicide resistance is a multi-dimensional problem, with impacts and management strategies specific to different crops, diseases and regions.
The risk of fungicide resistance is greatest where fungicides with a single mode of action are used repeatedly to control highly virulent pathogens in the presence of susceptible crop varieties, favourable weather conditions and less-than-ideal agronomic practices.
By taking advantage of AFREN resources, growers and advisers can better understand how to reduce the threat of fungicide resistance.
Its goal is to provide knowledge and understanding of best-practice management strategies to reduce the impact and emergence of fungicide resistance.
Specifically, AFREN has been established to deliver:
* A national fungicide resistance management guide
* Local information sessions and workshops
* Fact sheets, updates and email alerts
* Educational webinars.
Regionally specific resources are also being developed to help growers and advisers address the issue as it impacts their area and it is hoped by increasing awareness of occurrences, risk factors and best-management practices, the wider industry can limit the emergence and the impact of fungicide resistance in Australia.
“In the wheat trials, variety was a primary driver in differentiating disease prevalence at growth stages GS31 and two weeks post-GS39, with Septoria tritici blotch (STB) detected on lower leaves early in the season (GS31),” Yolanda says.
“At GS39, STB had migrated into the upper canopy in all varieties, and 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.
“Both variety and treatment imposed statistically significant effects on grain yield (t/ha).
“For example, between the untreated controls, LRPB Matador was the highest-yielding variety, and Scepter the lowest, illustrating the impact of disease.
“Within varieties, Scepter was the most responsive to disease control, with all but one treatment showing a significantly higher yield compared with the control.
“Double spray applications (GS31 and GS39) resulted in the highest yield for Scepter, with little difference between the economical and premium products.
“The partial gross margin (PGM) for treatment (GS31 and GS39 economical) showed a slightly higher return on investment (ROI), but the highest PGM for this variety was achieved with one application of propiconazole and benzovindifupyr at GS31.”
The research shows differences in yield between treatments 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 from one application of propiconazole and benzovindifupyr at GS39 versus the premium version of this treatment, which included Flutriafol.
The first treatment across both varieties showed high yields, and the highest PGM.
Yolanda says an interesting finding was the lack of significant differences between economical and premium products, regardless of variety or spray application.
However, she says PGM analysis showed in some instances for plots with relatively similar yields, the return on investment was higher for the treatment using economic products.
This was not always the case, but was significant.
“As observed for the wheat, barley establishment was aided by timely rain and soil moisture, and this was also likely to increase disease load,” Yolanda adds.
“Spot form net blotch (SFNB) was detected in every barley trial plot, and RGT Planet suffered substantially higher damage from SFNB than other varieties, which is unsurprising as this variety is considered more susceptible to this disease than Maximus CL and Leabrook,” she says.
“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.”
Both treatment and variety imposed significant effects on yield and variety for yield.
In the control plots, the mean yield in Maximus CL was significantly higher than those recorded for Leabrook and RGT Planet.
It is possible the difference in yield between Maximus CL and the other varieties was due to slightly lower disease loads for this variety later in the season.
Yolanda says given Leabrook is the more resistant variety to SFNB, this may indicate environmental conditions in this trial favoured Maximus CL.
She says unlike in the wheat trial, there were no varieties which responded strongly to treatments across the board, and for RGT Planet no disease management treatment resulted in significantly different yields compared to the control.
“Only one instance of significant difference between economic and premium products was detected; this was for treatments with Maximus CL where the economic treatment sprayed only at GS31 yielded higher than the premium treatment sprayed at GS31,” Yolanda says.
“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 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.”
Yolanda says interim findings of this project suggest complex interactions between variety choice and disease management strategy.
She says for wheat, Scepter is 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,” Yolanda says.
“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 variety susceptibility plays a significant role.
“BCG will continue this work to build on the data already gathered.”
