In light of growing concerns over fungicide resistance, the focus on plant health has emerged as the primary defence against pathogens.
Resistance has been the traditional approach, with the introduction of 11 varieties boasting robust Septoria ratings of 6.5 or above. Whilst new varieties help to maintain or grow yield, plants possess innate capabilities to resist diseases, prompting the assertion that ‘healthy plants can fight back’. This shift is significant as it reduces dependence on fungicides, especially with fewer products in the development pipeline.
Microorganisms within the soil ecosystem act as natural competitors, limiting resources available for pathogens. Additionally, the plant’s microbiome triggers its immune response, facilitating a dynamic defence mechanism. When the plant comes under attack, it will look to microbes in the soil to fight back. Through root exudates, the plant finds the correct organisms needed to boost its natural defence mechanism. Farmer, consultant and contractor Chris Leslie is using this method across the fields he manages in East Lothian, Fife and Angus.
Through careful plant and soil management, Mr Leslie manages to completely avoid fungicide usage in the more resistant varieties during dry years. Even those varieties more resistant need fewer applications and lower rates. Mr Leslie’s plan last year was made up of a ‘basic’ three-spray programme for conventional crops that were in good health.
If a crop had a Septoria rating of around 6.0 Mr Leslie applied a modest application of Wolverine (metconazole + fluxapyroxad) or Ascra (prothioconazole + bixafen + fluopyram) at T1 followed by Revystar (mefentrifluconazole + fluxapyroxad) at T2. This Mr Leslie points out costed less than many typical winter wheat disease control programmes and kept Septoria disease out. If the disease had become more prevalent then application rates would increase; however, his mantra is to avoid the disease in the first place.
To do this, Mr Leslie believes that the plant must have all it needs to be healthy. The first step is to use minimum or no cultivation establishment, then run a rotation and cover crop plan to get the soil chemistry, biology and physics right. To fine-tune application of inputs, soil and tissue testing happens throughout the season which improves timings of nitrogen (N) and nutrient applications.
Mr Leslie points out that getting the right amount of nitrogen into a plant is more down to the efficiency of uptake than the amount applied to the field. He goes so far as to question the linear line between N and yield up to 220 kg/N/ha, as he believes in a more circular approach which gets the whole soil biome working which in turn increases the nutrient availability to the plant.
The increased level of details means that Mr Leslie applies all nutrients variably including Sulphur which he thinks is critical for N uptake. He points out that whilst variable rate applications of N is well established other nutrients must also be available.
Sulphur applications have been on the rise with some fields now getting a kilo of S for every kilo of N. There is also a need to apply inputs more regularly with wheat crops typically getting four applications with the first being a 80kg/ha higher dose.
He is applying foliar products like Nufol in a concentrate form at 50 l/ha instead of the usual 100 l/ha 50:50dilution. This strategy is helping to get results with yields of 10 t/ha in 2023 which achieved a nitrogen level in the grain of 1.6%N from a total application of around 130 kg/N/ha. Put simply this should not happen when plotted against the textbook straight line N dose vs response graph.
The approach is helping to even out yields in fields with the min or no-till cropping hampering performance in the best areas of fields whilst making large gains in the poorer parts. Overall the improvements outweigh the drawbacks giving more yield. Much of the way Mr Leslie farms is about trade-offs with an overall gain. If a field manages to reduce spray rates to 75% for any azole + SDHI or Qii fungicide there are significant savings to be made. But for crops to remain healthy some of that saving must be reinvested in additional products, input rates or passes.
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