- Phoma leaf spot Jon West
Updated Phoma leaf spot forecast
Work done at Rothamsted Research has helped to update the Phoma leaf spot and stem canker forecasting done by AHDB.
Phoma is an important disease of Oilseed Rape crops with initial infection appearing as pale lesions on the leaves. These develop black specks, the fruiting bodies that release splash-dispersed spores.
The fungus grows without symptoms through the leaf to the stem where it incubates until early spring. Then rapid growth by the fungus produces a visible stem rot or canker.
Fungicide application timings are critical to ensure maximum effect. This is after the first significant release of spores in the autumn, ideally before more than 10-20% of plants have Phoma leaf spots.
The weather-based forecasting tool from AHDB forecasts the date when 10% of plants will have Phoma leaf spots. This can be a handy tool for the best time to apply fungicide to achieve good control. Visit the AHDB Phoma Forecast for more information.