Infectious disease is ubiquitous in nature, and hosts struggle to persist in the face of strong disease pressure. Innate resistance is a key trait that can facilitate host persistence, but the evolutionary dynamics of resistance can be complex, and sometimes result in unexpected outcomes. Our lab studies the ecological and evolutionary dynamics of a pollinator-transmitted sterilizing ‘smut disease’ of wild carnations. We have found that that hosts have evolved high levels of innate resistance to the disease, but that this resistance is age-dependent, providing high levels of protection to adults but leaving juveniles highly vulnerable to infection. In the first part of the talk, I will discuss the causes and consequences of age-specific resistance to disease, and its impact on host-pathogen persistence. In the second part of the talk, I will discuss new work on the impact of the environment on host resistance evolution.  We have recently found that summer temperatures can temporarily reduce the virulence and transmissibility of the smut pathogen, which could alter selection for host resistance traits.