Anomalous Dark Growth Rings in Black Cherry

Anomalous dark growth rings have been observed in black cherry (Prunus serotina) sawlogs from northwestern Pennsylvania making the logs unsuitable for veneer products. Thirty-six cross sections with dark rings, each traceable to one of ten stands, were obtained from a local mill and sections were dated and annual ring widths were measured. One or more dark rings were found in 30 of the 36 cross sections. The most frequent years in which dark rings formed were 1994, on 55% of cross sections, and 1995, on 72% of cross sections. Both years were coincident with widespread cherry scallop shell moth (Hydria prunivorata) outbreaks. GIS layers and maps obtained from the Allegheny National Forest were used to document cherry scallop shell moth defoliations in these stands. These rings show a darkened discoloration through all or portions of the annual ring without characteristics typical of gum spots or gum defects caused by traumatic injury from bark beetles or cambium miners. Microscopic examination of the rings revealed darkened fiber cell walls, but no other cellular abnormalities. Dark rings are more common in stands with a high proportion of the total basal area composed of black cherry. These stands also are more susceptible to repeated defoliations from cherry scallop shell moth.