Spatial and temporal development of beech bark disease in the northeastern United States

For most of a century beech bark disease has been spreading south and west from its point of introduction in Nova Scotia. The objective of this paper is to illustrate the impact of disease progression on beech trees across the northeastern United States. Beech trees were observed at each of 22 plots during summer months between 1979 and 1992. The plots were located throughout 7 States in the northeastern U.S. They are drawn from regions where BBD has been present for varying lengths of time, including some that have been affected for 50 years or more, and some that were first affected during the study. In general, plots were visited annually. Some areas were characterized by sharp increases in mortality shortly after the initial invasion of the disease and a subsequent lower constant mortality (consistent with a typical killing front and aftermath zone). In other cases, the killing front mortality was delayed or extended for decades. A small number of trees never became infested with scale, indicating probable strong resistance. Moreover, as many as 20% showed only slight scale activity, indicating probable partial resistance. Immediately following initial Nectria infection, trees that died quickly showed higher levels of fruiting than those that survived at least 5 years.