Two weather-based models for predicting the onset of seasonal release of ascospores of Leptosphaeria maculans or L. biglobosa

Weather-based models (Improved Blackleg Sporacle and SporacleEzy) to predict the date of onset of seasonal release from oilseed rape debris of ascospores of Leptosphaeria maculans or L. biglobosa , causes of phoma stem canker, were developed and tested with data from diverse environments in Australia, Canada, France, Poland and the UK. Parameters were estimated, using the same datasets from experiments in the UK and Poland, with an accuracy of root mean squared deviation ( RMSD ) of 7·4 (with a bias of − 4·54, L . maculans ) and 8·5 (with a bias of 0·30, L. biglobosa ) days for Improved Blackleg Sporacle, and of 2·9 (with a bias of − 0·06, L . maculans ) and 7·3 (with a bias of − 1·18, L. biglobosa ) days for SporacleEzy. When tested with data independent of those used for parameter estimation, overall predictions agreed well with observed data in five countries, both for Improved Blackleg Sporacle ( R 2 = 0·96, slope = 1·00, standard