Cercospora risk forecasting for 2023

The incidence of cercospora leaf spot has been rising in the UK leading to BBRO producing a risk forecasting model. This model has been active from the 1st June, closing on the 31st October 2023.

High risk warning has been triggered as shown by red areas on map below -11th September 2023. Infected crops are at high risk as this disease develops quickly. 

Leaf spores can develop from 5-21 days after infection. This depends on amount of inoculum and of course temperature and how wet the leaves have been. Spots typically appear on lower, older leaves first. Drought senesced or virus-infected leaves may also show symptoms quicker than healthy actively growing leaves.

BBRO will monitor levels of risk daily and where clear risk is identified growers will be contacted directly by text.  However, we encourage all growers to be vigilant in their own areas as pockets of rain will add to the humidity pressures.

The numbers shown on the map below indicates the level of risk to the crop of cercospora developing. When an area is deemed at risk the square will turn red, and should act as a prompt for you to check your crop for signs of cercospora.   The map below is only an indication of environmental conditions relating to increased disease pressure, it is not an indication of disease presence. Only spray if cercospora is found.

Values below 6 are not of a concern.

Below: Maps relate to the 26th September to 9th October. 

As expected the risk factors on the model have decreased, however we are seeing more incidences of cercospora in-field than the model predicted.  As a relatively new disease to the UK the model is based on data collected from the America and Europe, it may be that isolates in the UK are reacting differently to our maritime climate. We will be assessing the data and the spores caught this year and if required adapting the model.









For more info on the risk of cercospora and how/why BBRO are undertaking this work, please watch this video and read the FAQs below.



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We are set up jointly by British Sugar plc and the National Farmers' Union.

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