Caroline Dillard Outside Reading 4: 4/16/23

 I recently read many academic articles on how climate change affects the distribution range and prevalence of White Pine Blister Rust. Across rigorous studies on rust diseases, several environmental conditions, such as moisture and temperature, have been identified as major influences on the susceptibility of pines. One factor above all others, however, seems to be integral to pine infection. The key to predicting infection is the presence, proximity to, and abundance of the alternate host species of rust disease, Ribes spp. which includes gooseberries and currants. The presence of the alternate host is obligatory for a pine to become infected, such that if there is no Ribes present, there is no risk of rust disease. While other environmental conditions can impact a pine’s vulnerability to infection, the presence or absence of Ribes can change or negate that impact. For example, increased global warming as a result of climate change is predicted to shift the rust infection range into higher elevations exposing a new set of pine hosts, but there are less Ribes species at higher elevations, so the risk of disease is inherently lower. Another environmental condition which is ultimately connected back to the alternate host is the effect of stand density. Stand density, in regard to the alternate host, relates to the available space the wind-dispersed spores have to infect pines. A more open and exposed canopy has greater risk of infection. 

Learning all of this puts tree diseases in a more complicated context than I had thought of before. Many environmental factors affect why and how a disease is spread.