SkleroPro - a crop loss-related forecasting model for chemical control of Sclerotinia stem rot in winter oilseed rape in Germanyn

摘要

Sclerotinia stem rot (SSR) is an economically harmful disease in winter oilseed rape (OSR) in all regions with increased intensity of OSR cultivation. As resistant cultivars are not available, control of SSR relies on a routine fungicide spray at bloom in most areas. The economic evaluation of such sprays during the last fifteen years in Germany revealed 67% of fungicide treatments to be not cost-effective. Therefore, an economy-related forecasting model was developed based on disease/crop-loss relationships obtained from a three-year field experiment with a hybrid and a line cultivar. A further analysis demonstrated the significant impact of crop rotation, while crop density, nitrogen level and soil management did not have significant effects on disease incidence (DI). From a climate chamber study, 7 to 11°C and 80 to 86% relative humidity (RH) were established as minimum conditions for stem infection with ascospores and used in order to discriminate infection hours. DI significantly correlated with infection hours (Inh) occurring post growth stage (GS) 58 (late bud stage) (r2 = 0.42; P≤0.001). In a parallel ontogenetic model, the developmental stages of OSR are simulated. The novel forecasting system, SkleroPro, consists of a two-tiered approach, the first providing a regional assessment of the disease risk, which is assumed when 23 Inh have accumulated post GS 58. The second tier provides a field-site specific, economy-based recommendation, including costs of spray, expected yield and rapeseed produce price. In field evaluations of SkleroPro the percentage of economically correct decisions varied from 70 to 81%, with potential savings of fungicides of 39 to 81% in individual years. This study demonstrates that in areas with abundant occurrence of sclerotinia the level of SSR in OSR can satisfactorily be determined by predicting stem infection during late bud and flowering and a simulation of apothecial development is not required. SkleroPro is the first crop-loss related forecasting model suitable for practical use in the control of a Sclerotinia disease and available to users in Germany via the internet since 2006. Its concept and components may be useful in developing forecasting systems for sclerotinia diseases in yet other crops.