Prediction of the date of onset of phoma leaf spot epidemics on oilseed rape in the UK

To reduce reliance on fungicides for control of oilseed rape diseases, Decision Support Systems (DSS) are being developed to target applications as part of an integrated disease management strategy. This paper reports on the development of an empirical model for predicting risk of severe phoma stem canker epidemics. Meteorological data are used to predict the date when incidence (% plants affected) of phoma leaf spot can be expected to reach 10%. This incidence has been suggested as an appropriate threshold to guide timing of fungicide applications against this disease to prevent pathogen spread from leaf to stem and the subsequent development of damaging stem cankers. The 10% phoma leaf spot forecast can be extended, using further meteorological and cultivar resistance rating data, to predict the date of canker onset, canker severity at harvest and subsequent yield loss