This is a review of Caseys et al. bioRxiv doi: https://doi.org/10.1101/507491 posted on June 25, 2019. This study aims at addressing whether coevolutionary models of host-pathogen interactions apply to a generalist pathogen that exhibits quantitative virulence across a broad range of plants. They generated an exhaustive virulence matrix for the nectrophic fungus Botrytis cinerea on 90 genotypes of 8 plant species. They conclude that this pathosystem doesn’t fit traditional arms-race coevolution models with quantitative variation in susceptibility distinct from the phylogenetic relationships between the examined plants.