PARAMETER-ESTIMATION FOR A DESCRIPTIVE EPIZOOTIOLOGICAL MODEL OF THE INFECTION OF A CEREAL APHID POPULATION BY A FUNGAL PATHOGEN (ENTOMOPHTHORALE)

A descriptive epizootiological model is proposed and parameterized to predict the dynamics of the host-pathogen system ''Cereal aphid - ento mophthoralean fungus Erynia neoaphidis''. The model partitions the hos t population into distinct classes corresponding to fungal development stages. The dynamics of each class density are described by a set of non-linear ordinary differential equations with the reciprocal of esti mated parameter giving average transit or developmental times. The mod el is compared to the biological data. The experiment was performed un der controlled conditions of 20 degrees C and RH > 95% using the cerea l aphid Sitobion avenae as the host. The stability of the model was ex amined and indicated periodic oscillations, i.e. epizootic intervals s eparated by ion enzootic periods. In addition, Lotka-Volterra mass act ion assumption for transmission rate was tested using the data.