Understanding the risk of rusts in changing climates

We have yet to understand how climate change and associated drought will alter interactions between rust species and their native hosts. Non-native rusts including Cronartium ribicola, the non-native rust fungus that causes the lethal white pine blister rust (WPBR) in five-needle pines, and Austropuccinia psidii, causal agent of myrtle rust, have spread through many ecosystems around the world, aided by high fecundity and wind dispersed spores. Though many tree species become more vulnerable to native pathogens during water stress, little is known about the interactions between native host species and invasive rusts under changing climate and as invasive pathogens are introduced into new areas. Using white pine blister rust as a model system, we characterized drought response and disease progression in the severely droughted, moderately droughted and well-watered P. flexilis challenged with C. ribicola, and we identified a hybrid rust between a native rust and C. ribicola that may lead to novel strains. These results provide an understanding of how host-pathogen interactions within the WPBR pathosystem may change in western forests as drought induced by climate change continue occur, and also provide insights into how myrtle rust may change and adapt to changing climates.