Epidemiology for Hazard Rating of White Pine Blister Rust

Abstract

The ability to assess the potential for a severe infestation of white pine blister rust is an important management tool. Successful hazard rating requires a proper understanding of blister rust epidemiology, including environmental and genetic factors. For the blister rust caused by Cronartium ribicola, climate and meteorology, and the ecology, distribution, and pathology of ribes and other telial hosts affect spread and intensification of rust on white pine hosts (several sections in subgenus Strobus of genus Pinus). The importance of ribes (genus Ribes) for supporting effective inoculum production varies according to differences in susceptibility, diversity, distribution, and abundance by taxon and population. Temperature and humidity regimes and air circulation patterns at micro to synoptic scales influence the development and dispersal of the rust. Spatial and temporal variations in the dispersal processes are expressed as differences in rust severity distributions. These differences can be mapped as hazard zones and used to choose among alternative management prescriptions. When C. ribicola was first introduced to North America, its epidemiological behavior displayed a limited range of hosts and environments. The diversity of related rusts, however, suggests that C. ribicola may have the capacity to adapt to previously unrecognized hosts and environments. Pine populations have also shown some ability to respond with lower susceptibility to this introduced pathogen, indicating that the North American pathosystems are dynamic and evolving. Efforts to manage such high-elevation species as whitebark pine would be aided by continued research in the epidemiology of this pathosystem in diverse hosts and environments.