Disease detectives: mapping the risk of invasive forest pathogens under a changing climate.
Brown root rot (caused by Phellinus noxius) and myrtle rust (caused by Austropuccinia psidii) are natural disturbances in their native tropical and subtropical forest ecosystems. A tree infected with either fungal pathogen becomes unhealthy and likely dies, sometimes within 3 months. These pathogens are threatening forest ecosystems around the world as they spread through international trade or other means, such as by wind or through the soil. Climate change also is creating environmental conditions that will allow these pathogens to survive in novel forest ecosystems where they haven't been found historically. An international team headed by researchers with the USDA Forest Service and Colorado State University analyzed the genetics of the two pathogens and mapped their likely spread based on the current locations of the various subgroups of each pathogen and contemporary and projected future climates. They found that distinct genetic subgroups of each pathogen occupied different ecological niches and caused varying damage to host trees. The genetic diversity of these pathogens creates a potent threat, and this information is critical for agencies that regulate trade. The Hawaii Department of Agriculture, for example, is working with the USDA Animal Plant Health Inspection Service to prohibit the importation of plants in the myrtle family from locations where myrtle rust pathogens of a specific genetic subgroup are known to occur.