Long-term changes in fusiform rust incidence in the southeastern United States
Fusiform rust is the most devastating disease of slash pine (Pinus elliottii) and loblolly pine (Pinus taeda) in the southeastern United States. Since the 1970s, the USDA Forest Service Forest Inventory and Analysis (FIA) Program has assessed fusiform rust incidence on its network of ground plots in 13 states across the southeastern United States. Through analysis of the FIA data, we found that current fusiform rust incidence varied by state, forest type, and stand origin and that across all stand ages, rust incidence was approximately equal in planted and natural stands of loblolly pine but was higher for planted versus natural stands of slash pine. Decreases in rust incidence over the last 30–40 years were evident in young planted loblolly pine stands but not in young planted slash pine stands. Results for slash pine were surprising, and the reasons remain unclear but one reason may be planting stock origin, which was unknown and may be highly variable in rust resistance. These analyses of FIA rust incidence data also were used to update the original rust disease hazard maps published by Starkey et al. (1997).