Predators, host abundance, and host spatial distribution affect the movement of wingless non-colonizing vector Rhopalosiphum padi (L.) and PVY prevalence in an oat/potato system

Abstract

In the study of insect-vectored plant viruses, colonizing vector species remain the focus. However, non-colonizing vector species, those that do not settle and reproduce on the viral plant host, are often the most abundant in the field and may be the largest contributors to disease spread. While non-colonists may have a substantial effect on disease prevalence, the factors influencing their movement and transmission on non-host plants have been little studied. Here we evaluated how a common biological control agent (Hippodamia convergens), host and non-host plant abundance, and plant spatial distribution impact the movement and density of a wingless non-colonizing vector [Rhopalosiphum padi (L.)] and transmission of potato virus Y (PVY) in potatoes in experimental arenas. The results of this work illustrate the importance of plant species function (host or non-host) and distribution to vector behavior and disease spread. Predation, host plant abundance, and plant spatial distribution interactively affected viral prevalence within infected arenas. Increasing the number of vector non-host plants increased the distance and frequency of aphid movement, and the effect was influenced by plant spatial distribution, the arrangement of plant species in the experimental arena. Increasing the number of vector host plants increased the density of aphids. Although the interaction of the plant and predator treatments affected the proportion of potato plants infected in arenas where infection occurred, and host abundance and spatial distribution impacted vector movement and viral prevalence, aphid movement did not appear to mediate the effect of plant and predator treatments on PVY prevalence. This work demonstrates that both wingless non-colonizing vector behavior and transmission are aggregated responses to multiple environmental drivers.