Unveiling a Hidden Menace: Invasive Tree Pathogens, Less Known but Increasingly Threatening Southern Hemisphere Forests

Forest pathogens have repeatedly restructured ecosystems in the Northern Hemisphere, where epidemics such as chestnut blight, Dutch elm disease, and sudden oak death eliminated foundation species and reshaped landscapes. In contrast, the Southern Hemisphere, buffered by geographic isolation, unique floras, and historically lower trade volumes, experienced comparatively few incursions until recent decades. These barriers are rapidly eroding due to globalization, climate change, and the expansion of industrial plantation forestry dominated by exotic species of Pinus and Eucalyptus . These vast monocultures with low genetic diversity have created highly susceptible production systems that can amplify epidemic spread and act as sources of novel pathogen emergence. Drawing on lessons from the Northern Hemisphere, this review highlights the escalating risk of forest epidemics in the Southern Hemisphere and calls for proactive, coordinated responses. Stringent phytosanitary standards, advanced diagnostic techniques, and risk-optimized surveillance must be paired with collaborative breeding programs that prioritize resistance in high-risk hosts. At the same time, international cooperation across science, policy, industry, and communities is essential to strengthen prevention, support early detection, and enable rapid response. The resilience of Southern Hemisphere forests, both native and plantations, will depend on shifting from reactive management toward integrated, globally coordinated strategies that recognize the shared nature of pathogen threats.