A STOCHASTIC SIMULATION-MODEL OF EPIDEMICS OF ARTHROPOD-VECTORED PLANT-VIRUSES

A generalized theoretical model was developed of the spread of a virus from a single source plant in a small field. Input parameters include probabilities of virus acquisition and inoculation, lengths of latent periods in the plant and vector, length of the vector infectious peri od, number of vectors per plant, and the amount of vector movement. De cisions about acquisition, inoculation, and vector movement are made o n the basis of the values of pseudorandomly selected numbers. Output i ncludes numbers of viruliferous vectors and positions of infected plan ts at each iteration. Simulation runs were performed for viruses with four generalized types of vector transmission: nonpersistent, semipers istent, circulative, and propagative. Model predictions were generally consistent with expected natural spread. Results of simulation runs i llustrated the great effects that the amount of vector movement can ha ve on disease dynamics and spatial distribution, particularly for dise ases transmitted in a nonpersistent manner. The model will be difficul t to fully validate; however, it provides a logically rigorous way of integrating knowledge about the many processes that affect virus disea se epidemics and may be useful in the development of methods of analys is and in the development of less complex models.