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.

Beech scale, Cryptococcus fagisuga Lindinger, is a non-native invasive insect associated with beech bark disease. A quantitative method of measuring viable scale density at the levels of the individual tree and localized bark patches was developed. Bark patches (10 cm(2)) were removed at 0, 1, and 2 m above the ground and at the four cardinal directions from 13 trees in northern New York and 12 trees in northern Michigan. Digital photographs of each patch were made, and the wax mass area was measured from two random 1-cm(2) subsamples on each bark patch using image analysis software. Viable scale insects were counted after removing the wax under a dissecting microscope. Separate regression analyses at the whole tree level for the New York and Michigan sites each showed a strong positive relationship of wax mass area with the number of underlying viable scale insects. The relationships for the New York and Michigan data were not significantly different from each other, and when pooling data from the two sites, there was still a significant positive relationship between wax mass area and the number of scale insects. The relationships between viable scale insects and wax mass area were different at the 0-, 1-, and 2-m sampling heights but do not seem to affect the relationship. This method does not disrupt the insect or its interactions with the host tree.