Myrtle rust is a plant disease caused by the fungal pathogen Austropuccinia psidii. Numerous members of the Myrtaceae plant family are impacted by this disease to varying extents. This study focused on watergum (Tristaniopsis exiliflora) to explore the climatic and microclimatic preferences of the myrtle rust disease. High annual rainfall, maximum temperatures below 32°C, dense canopy cover and the presence of flood plains were all associated with increased severity of myrtle rust on watergum. Conservation efforts should focus on Myrtaceae species with narrow climatic distributions that occur within the optimal climatic conditions for myrtle rust.