Assessing the Potential Susceptibility of Eucalyptus deglupta Blume to Austropuccinia psidii (G. Winter) Beenken in Mindanao, Philippines

Abstract. Austropuccinia psidii is an invasive fungal pathogen that poses a threat to Myrtaceae species worldwide. While several studies attempted to model its potential distribution, many lack geographical specificity, particularly concerning the Philippines. Despite the absence of occurrence record in the Philippines, the increasing number of reported invasions in Southeast Asian countries highlights the urgency of assessing its potential spread in the country. Environmental conditions from 333 consolidated global occurrence points showed the pathogen’s preference for warm climates and moderate temperature fluctuations, alongside a broad tolerance for elevation and precipitation. When applied to Mindanao, results revealed that approximately 62,500 km2 are environmentally suitable for the pathogen. MaxEnt modeling of Eucalyptus deglupta identified about 26,800 km2 as suitable habitat, particularly in Eastern Mindanao and parts of BARMM. The model’s AUC value of 0.7252 indicates fair predictive accuracy, with slope, isothermality, and precipitation of the coldest quarter contributing most to habitat suitability. Overlaying the binary suitability maps for both species showed that around 15,300 km2, primarily in Eastern Mindanao, are potentially suitable for both E. deglupta and A. psidii. Davao Region has the highest susceptible area at 5,713 km2. Bukidnon, Davao de Oro (Compostela Valley), and Agusan del Sur have the largest susceptible areas among the provinces, while Baganga, Davao City, and Laak are the most susceptible municipalities. These findings highlight critical areas that warrant close monitoring for potential myrtle rust outbreaks. Continued research is recommended to refine environmental parameters, enhance model robustness, and support early detection and mitigation strategies.