Conclusions
Through controlled quantitative experiments, we were able to disentangle the impacts of temperature, host phenology, host resistance and host offspring type (sexual vs asexual) on the timing of seasonal disease outbreaks that are repeatedly observed in nature in a well-studied host-parasite model system where host and parasite overwinter separately. We provide several lines of evidence that parasite infection is strongly driven by temperature, beyond the effects of temperature on host development, and that this relationship is modified by host resistance and offspring type. This work highlights the importance of understanding how hosts and parasites may respond differently to environmental changes and provides insight into the seasonality of epidemics, particularly for parasites with free-living stages. It also allows us to improve our predictions regarding the response of infectious disease outbreaks to climate change.