What levers can be mobilised to manage the risk of septoria leaf spot on wheat?

Each year, septoria devastates thousands of hectares of soft wheat in Europe, especially in France, where losses sometimes exceed 25%. Conventional methods can be used to prevent the development of the septoria leaf spot, such as variety selection or late sowing. Plant defence stimulators can also help limit parasite pressure.

Septoria symptoms and spread of the disease on wheat crops

protect septoria wheat defence stimulators

Septoria remains the single most common disease affecting soft wheat in Europe. In France, average losses on a national scale over the past 10 years have been 17 quintals per hectare.

Septoria can be recognised by the leaf spot it causes. These may be long, white spots or oval or rectangular brown spots. The highly visible little black dots speckling the spots are characteristic of the disease.

The disease spreads upwards on the plant. With ambient humidity and rain, the spots fill with water and swell. They then release spores from the base towards the top of the plant, with splash dispersal spreading the disease towards the upper leaves.

When should septoria disease on wheat be treated?

It is essential to take into account the physiological stage of the plant when treating the disease. Septoria disease is generally treated at the 2-node stage, i.e. when the second leaf has appeared starting from the top of the plant. If the wheat observed shows septoria leaf spot, it is recommended that it be treated before the next rain. For more sensitive varieties (scored 7), the affected leaf level reduced by 50 %.

What methods should be used to manage the septoria leaf spot risk in wheat?

Variety is the main tried and tested lever for optimising the agronomics and limiting the pressure of leaf disease risk factors.
In addition to the choice of variety, other agronomic factors can be used to reduce the risk of septoria:

  • Late-sown wheat will have less chance of being affected. The inoculum is then lower at the end of winter.
  • High densities are associated with stronger disease pressure, but their effect remains irregular. Conversely, very low densities may limit disease pressure but yields will obviously suffer.
  • Wheat on wheat rotations and the presence of surface residues can promote the disease.

Optimising the mineral nutrition of wheat is an effective approach

Ensuring appropriate nutrition is clearly not enough in itself to manage the risk of leaf disease. However plant defence stimulators (PDSs), by their very nature, share a number of characteristics, i.e. the PR protein, an enzyme involved in the synthesis of salicylic acid, a phytalexin or peroxidases. PDSs act on the whole plant rather than the pathogen. PDSs help the plant optimise its production potential and thus pave the way for increased yields. These can be as much as 25% with respect to the losses that septoria disease can cause.

Consequently, not all cases of established septoria necessarily lead to loss of the harvest. Prevention remains the best method for managing the risk of development of this disease. The choice of variety, rotation and optimisation of nutrition are all methods that should be incorporated into the good practices implemented. Our experts can help you tackle this problem: don’t hesitate to contact them.


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