Summer 2024 15 beech scale (Cryptococcus fagisuga), the nonnative, piercing and sucking insect associated with the disease complex. The advance front typically last three to six years before progressing to the killing front. As the name suggests, the killing front occurs when the fungi (Neonectria faginata and N. ditissima) have successfully colonized the trees, resulting in visible symptoms and widespread mortality. The characteristic symptoms of beech bark disease are bark cankers, which are sunken, dead areas on the bark of the tree and a reduced canopy. Following the heavy beech mortality associated with the killing front, the aftermath stage has reduced levels of the beech scale and fungi due to the lack of mature beech remaining in the forests. Aftermath forests are dominated by small beech that take over the entire understory of the forest. There is little mortality from beech bark disease in aftermath forests until the trees reach a DBH of approximately 15 inches. Beech bark disease impacted stands in Virginia are currently in the aftermath phase. Despite the loss of American beech trees, arguably the most ecologically damaging consequence of beech bark disease is the increased proliferation of young beech saplings in the understory, also known as beech thickets. Beech thickets greatly reduce the understory diversity and outcompete native vegetation, such as spring ephemerals in the Southern Appalachian forests. Furthermore, beech thickets significantly inhibit or eliminate woody regeneration, resulting in stands that are inadequately stocked and require management intervention to increase the recruitment of more desirable species. Since beech do not begin producing beechnuts until they are approximately 40 years old, the reduction in an overstory mast species negatively impacts the mammal and bird species within a forest, and the unpalatable beech leaves may further decrease the presence of herbivores within a beech stand. Unlike other forest diseases like chestnut blight, beech bark disease alone does not eliminate beech from the forest; instead, it changes its function from a dominant overstory species to an understory woody shrub. Beech leaf disease Unlike beech bark disease that has impacted beech for almost a century, beech leaf disease is an emerging disease that was only recently discovered. The disease was first identified in Ohio in 2012 and has since spread throughout 15 states including Virginia, and Canada (Figure 1). Along with American beech, European (Fagus sylvatica), Oriental (F. orientalis), and Chinese (F. engleriana) beech are also susceptible to the disease, and symptoms of beech leaf disease have been identified on these species in nurseries and arboretums. Symptoms of beech leaf disease include interveinal darkening of the leaves (referred to as banded symptoms), thickened and darkened leaves that appear shriveled (referred to as crinkled symptoms), and dead buds that do not produce leaves during the growing season. Mature trees succumb to the disease in approximately seven years, but beech saplings can succumb to the disease much faster depending on the level of infestation. Characteristic canker symptoms of beech bark disease on severely impacted American beech trees. FIGURE 1. Current distribution of beech leaf disease.
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