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Beech bark disease: an evaluation of the predisposition hypothesis in an aftermath forest



The beech bark disease (BBD) complex affecting American beech consists of the scale insect, Cryptococcus fagisuga, and one or more pathogenic fungi of the genus Neonectria. Following extensive above-ground mortality of mature beech, stands can be defined by a characteristic set of conditions that are termed the aftermath zone. A long-standing hypothesis states that C. fagisuga is a necessary predisposing factor for Neonectria infection. Although some evidence supports this in the killing front, the relationship has not been examined in the aftermath zone and other predisposing factors have been proposed. Using quantitative, tree-level data, we found no significant relationships between C. fagisuga and Neonectria spp. in aftermath stands of central New York State. We propose that the pathosystem operating in the aftermath zone differs from that in the killing front in that C. fagisuga may not be the sole predisposing factor.