Diplodia sapinea causes Diplodia tip blight (DTB) and is recognised as an opportunistic necrotrophic pathogen affecting conifers. While DTB is associated with abiotic stress, the impact of biotic stress in the host on D. sapinea’s lifestyle shift is unknown. Observed co-occurrences of D. sapinea and Melampsora pinitorqua, causing pine twisting rust on Scots pine ( Pinus sylvestris), instigated an investigation into their interaction with and influence on the defence mechanisms of the host. We hypothesised that M. pinitorqua infections predispose the trees to D. sapinea by stressing the host and altering the shoot metabolites. Trees in a pine plantation in central Sweden were sampled over time to study pathogen biomass and host metabolites. The symptoms of both pathogens were consistent over years, and the preceding season’s symptoms affected the metabolic starting points pre-infection and M. pinitorqua’s proliferation. Symptoms of M. pinitorqua altered shoot metabolites more than fungal biomass, with co-symptomatic trees exhibiting elevated M. pinitorqua biomass. D. sapinea’s biomass pre-symptoms was independent of previous disease symptoms and infection by M. pinitorqua. Some trees showed tolerance to M. pinitorqua, with delayed rust infections and minimal DTB symptoms. This trait may improve the resilience of pine plantations, but more work is needed.