A dynamical model for epidemic outbursts by begomovirus population clusters

Begomovirus is a genus of highly destructive plant viruses that belongs to the family Geminiviriade and spreads through a single vector, the whitefly Bemisia tabaci. Although an old family of organisms, begomovirus has recently emerged as a potent threat to large-scale cultivation of crops. It is a threat with a very wide domain of influence and it can infect a very wide range of green plants cultivated for both sustenance and as cash crops.We introduce a mathematical model that simulates the complex dynamic interaction between begomovirus genetics, their adaptability to certain plants, and the availability of those plants to the virus under different cropping patterns. The model captures many empirically observed patterns of begomovirus epidemic outbursts, even if the equations do not directly depend on the genetics of begomovirus strains, and simply assume the vector to be ubiquitous. The model is formulated as a population dynamic system of differential equations, with nonlinear interactions between plant availability and begomovirus dynamic adaptability to different crop species. It also includes spatial diffusion allowing simulations over multiple neighboring regions.The ability of such a model to reproduce qualitatively correct epidemic structures indicates that the main reason for epidemic outbursts and the global spreading of the disease could be found in the patterns of inter-species interactions, many of which are human-induced. If this is the case, then the key to mitigating begomovirus epidemics would be the modification of agricultural practices. In particular, the use of intensive cropping patterns and resistant cultivars triggers aggressive virus adaptability through mutation speed-up. It seems that the only simple recourse would be to develop more diverse and less concentrated cropping patterns, both in cropland extent and in time.