Beech seed orchard development: Identification and propagation of beech bark resistant American beech trees
|Authors:||Jennifer Koch, Jill Rose.|
|Type:||General Technical Report|
|Station:||Southern Research Station|
Beech bark disease (BBD) has long been negatively impacting the American beech (Fagus grandifolia), an important component of hardwood and mixed hardwood forests throughout eastern North America that provides food and habitat for over 40 species of birds and mammals (McCullough and others 2001). BBD is initiated by feeding activities of the beech scale insect (Cryptococcus fagisuga), which create wounds that act as entry points for the Neonectria spp. fungi. It is the fungal component of the disease complex that weakens and kills the tree. Mortality levels in the rst wave of the disease can be as high as 50 percent (Miller-Weeks 1983). Surviving beech trees are often severely deformed, and their tendency to produce root sprouts can result in the formation of “thickets” that prevent regeneration of resistant beech or other species. The deformed trees offer no economic value and severely reduced ecological value as the disease continues to kill susceptible beech over time (Morin and others 2007). Fortunately, there are American beech trees that remain healthy despite intense BBD pressure. Studies have shown that when eggs are directly afxed to the bark of such trees, scale insects fail to establish, indicating that these trees are resistant to the scale insect (Houston 1983, Koch and others 2010). In the absence of feeding by the beech scale insect, there is little opportunity for Neonectria to invade, minimizing impact of the fungus. Large-scale mortality levels in beech due to Neonectria have never been reported in the absence of the insect, so resistance to the beech scale insect equates to resistance to beech bark disease.