Mn in apple leaves rose to a late summer maximum prior to or at abscission. The average levels, or the maxima, were not related to the severity of IBN symptoms. There are indications, but no conclusive evidence, that some withdrawal into the bark of shoots may occur. If such movement does occur, the resulting increase in bark Mn concentration is not great and cannot account for levels of bark Mn associated with IBN by Berg, et al. (1). No redistribution of Mn between bark and wood appears to occur during the winter.
Paper No. 2833 of the Journal Series of the North Carolina State University Agricultural Experiment Station, Raleigh, N. C.