Interactions in a host plant-virus-vector-parasitoid system: modelling the consequences for virus transmission and disease dynamics.

A full understanding of plant virus epidemiology requires studies at different scales of integration: from within-plant cell processes to vector population dynamics, behaviour and broader ecological interactions. Vectors respond to cues derived from plants (both healthy and virus-infected), from natural enemies and from other environmental influences, and these directly affect the temporal and spatial patterns of disease development. The key element in linking these scales is the transmission process and the determining factors involved. We use a mathematical model to show how the presence of natural enemies, by increasing virus transmission, can increase the rate of virus disease development while at the same time reducing vector population size, supporting recent empirical evidence obtained in microcosm studies. The implication of this work is that biological control of arthropod pests, which are also virus vectors, using parasitoid wasps, may have unanticipated and negative effects in terms of increased incidence of virus disease.