Influence of Leafhopper (Homoptera: Cicadellidae) Gender and Female Mating Status on Plant Disease Dynamics within a Simple Habitat

Abstract

The influence of leafhopper, Graminella nigrifrons (Forbes), gender and female mating status on the disease dynamics of leafhopper-transmitted maize chlorotic dwarf machlovirus was examined in a maize, Zea mays L., monoculture. Physical maps of disease incidence showed that diseased plants resulting from the release of males at the center of plots were less aggregated than for female treatments. Disease gradient slopes were compared after fitting the data to the log-logistic disease spread model. The release of males resulted in a mean disease gradient slope that was significantly more shallow than female treatments. Disease dispersion was further characterized using Lloyd's patchiness index, which yielded results that confirmed the analysis of disease gradients. These measures of dispersion also indicated a tendency for disease aggregation resulting from virgin females to be intermediate to males and mated females. Although the level of aggregation was most different for male and mated female treatments, there was no Significant difference between these treatments for overall disease incidence, indicating that the pattern of disease spread, but not overall disease incidence, was influenced. Whereas previous studies have focused on the role of host plant finding by leafhoppers as a determinant of individual movement behavior within a habitat, and consequently pathogen spread, our results suggest that an understanding of mating behavior may contribute to our understanding of plant disease dynamics.