Vector-borne plant pathogens frequently alter host-plant quality and associated plant cues in ways that influence vector recruitment and pathogen acquisition. Furthermore, following acquisition by the vector, pathogens may influence subsequent vector behavior either directly or via effects on the host plant. Given that such effects have significant implications for pathogen acquisition and inoculation, selection might be expected to favor patterns of pathogen effects on host-vector interactions that are conducive to transmission. Consequently, we might also expect to observe broad similarity in the effects of pathogens sharing similar modes of transmission. Here we discuss some specific hypotheses arising from these expectations and the implications of recent empirical findings. On the whole, this evidence is consistent with the expectation that pathogen effects on host-vector interactions are often (though not always) adaptive with respect to transmission.
