Assessment of epidemiological parameters and their use in epidemiological and forecasting models of cereal airborne diseases

Assessments of epidemiological parameters (e.g. infection efficiency, latent period, spore production) are required for the prediction of epidemic progress, for the estimation of components of partial resistance for different host plant cultivars and for the estimation of fitness components of pathogen isolates, A critical evaluation of methods of measurement of monocyclic parameters is presented, suggesting improvements by using more accurate techniques and taking into account different biotic and abiotic factors. Examples of influence of lesion density and age, of meteorological factors and of nutrient status of the host on cereal powdery mildew and rust epidemiological parameters are presented, The use of the ratio of mature lesions rather than the latent period for the estimation of the development rate of the fungus is suggested to allow comparison of a large number of individuals. It is feasible to assess the pathogen biomass by the sterol contents. The need lo verify by field experiments epidemiological parameters assessed under controlled conditions is pointed out, Finally, the way to include these monocyclic parameters in epidemiological and forecasting models is discussed using the case of wheat brown rust epidemics.