Anomalous dark rings found in black cherry (Prunus serotina Ehrh.) sawlogs have been anecdotally related to defoliations from cherry scallop shell moth (CSSM) (Hydria prunivorata Ferguson). Using six timber harvest sites on the Allegheny National Forest and a thinning on the Kane Experimental Forest in northwestern Pennsylvania, we documented the occurrence of dark rings in the 1970s, 1980s, and 1990s, concurrent with historical CSSM defoliations. Thirty cross-sections sampled from six

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... National Forest sites showed that dark rings formed on 18 sections in the 1970s, 17 sections in the 1980s, and 5 sections in the 1990s. Fourteen cross-sections had multiple (2-4) dark rings. Anatomical studies show the dark rings formed in these three decades have similar characteristics: darkened and thinner (>50 percent) fiber cell walls than normal-colored fiber cell walls. A long-term Kane Experimental Forest study was thinned in 2011-12, and dark ring frequency on recently cut stumps ranged from 48 percent to 68 percent across three replications. Dark rings in 12 of 20 cross-sections were associated with a ≥50 percent growth reduction in mean ring width during 1982-84. These results show that dark rings are associated with CSSM defoliation and that growth may be significantly reduced by defoliation.