New forecasting model can help to predict outbreaks of onion downy mildew

Milioncast, a new model that forecasts the risk of onion downy mildew based on a farm's environment, works by calculating the disease's sporulation, leaf wetness and latent period.

This is the claim of Warwick HRI's Dr Roy Kennedy, who developed the forecasting model now available on the latest version of MORPH4.

Kennedy said: "In some Defra work we have constructed a new model that can help you forecast the occurrence of this pathogen based on environmental readings taken from the crop.

"If you have the software you can feed these through and predict various aspects of the life cycle of onion downy mildew."

He told growers at last week's HDC Vegetable Technology Day that the model has been proven to have had an 81 per cent success rate at predicting outbreaks. This is compared to other models, such as Downcast, which had a 69 per cent success rate, and Onimil, which had 63 per cent success.

Kennedy said the system is effective because it takes into account three risk factors:

- the effect that temperature and humidity have on sporulation of the disease;

- the minimum leaf wetness that is required for infection to occur;

- the infection's latent period (the time it takes for symptoms to appear on the plants).

Kennedy said: "At 5 degsC it takes over 50 days between infection and symptoms, while at 15 degsC it takes less than 10 days."


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