Initial disease severity

The initial disease severity (Sevini, 0-1) used to initialize the epidemiological model (DiseaseProgress component) can be derived at the day of disease onset or inserted as a fixed value according to visual assessments. The InoculumPressure component provide models to simulate the suitability of the environmental conditions to the development of primary inoculum. The initial disease severity can be derived as:

where Sevmax is the maximum percentage of host tissue which can be affected by the epidemic at the disease onset (0-1) and Sevlast is the final value of disease severity of the disease in the previous cropping season (0-1). This relationship has to be determined for each pathosystem, e.g., by developing a multiple regression model to be tested against visual disease assessments.

This formalization, even developed with strong assumptions and not evaluated against real data, allows to consider the impact of the previous epidemic and of the agrometeorological conditions experienced by the pathogen population during the non-crop period on the initial disease severity value. This approach can be used to perform scenario assessments (e.g., crop yield forecasting, climate change studies), which involves the need of spatially distributed simulations. In these conditions the in-field measurement of initial disease severity is impossible, therefore the consideration of the climate suitability of a pathogen via process based models (infection model, spore dispersal) is essential to capture the interannual variability of climatic conditions and their influence on the inoculum load.

Created with the Personal Edition of HelpNDoc: iPhone web sites made easy