Vector behavior and pathogen spread: Implications of host plant resistance versus tolerance

Ecological theory suggests that vector preference for infected versus uninfected hosts can impact dramatically disease prevalence. However, little information exists on how vector behavior interacts with host resistance or tolerance to pathogens. Distinguishing between resistance and tolerance may be important epidemiologically if these traits are uncorrelated. Resistance is defined as a relative lack of infection whereas tolerance equates to infection without symptoms. We used a vectored “SIS” epidemiological model to simulate disease dynamics of a bacterial pathogen, Xylella fastidiosa, which is transmitted by sharpshooter leafhoppers to grapevine varietals that may differ in their relative resistance or tolerance to the pathogen. Results suggest that disease prevalence depends on several factors, including vector population size, vector discrimination against infected vines, and vine recovery rate. Notably, tolerant non-resistant varietals lead to the highest prevalence, because they weaken the potential for vector discrimination to temper pathogen acquisition and spread. We then conducted a choice transmission experiment (1 infected vine, 1 uninfected vine) for one grapevine varietal with the blue-green sharpshooter (Graphocephala atropunctata) at different periods after initial infection. The results of this experiment highlight the potential for vector discrimination to limit acquisition and spread of X. fastidiosa.