Unveiling a hidden menace: Invasive tree pathogens, less known but increasingly threatening Southern hemisphere forests

Over the last century a handful of tree diseases reshaped whole landscapes in the Northern Hemisphere. Chestnut blight, Dutch elm disease and sudden oak death each wiped out trees that whole ecosystems depended on.

The Southern Hemisphere was largely spared. Distance, unusual native plants and less trade kept most tree diseases out. In a review for the Annual Review of Phytopathology, Treena Burgess and Mike Wingfield show that this protection is wearing thin. Global trade moves plants, wood and soil faster than ever, the climate is changing, and plantations of pine and eucalyptus now cover large areas.

Those plantations are a particular concern. They are large blocks of closely related trees of one kind, grown far from where they evolved. A disease that finds a weak spot can spread through them quickly, and plantations can become the place where new diseases first appear.

Why it matters: the authors call for a switch from reacting to outbreaks to preventing them. That means strict plant health checks at borders, better tools for diagnosing disease, surveillance aimed where the risk is highest, and breeding programmes that put resistance first. Because diseases do not respect borders, scientists, governments, industry and communities need to work on this together.