A^EW York Agricultural, Experiment Station. 251 



winter-injured bark frequently becomes stained by the diffusion 

 into it of some substance apparently originating in the disintegrating 

 protoplasm of the affected tissues after resumption of vegetative 

 activities in early spring, thus giving rise to " black-heart." Often 

 the stained wood is then invaded by hymenomycetous fungi which 

 decay the discolored parts and sometimes portions of unstained wood, 

 thus resulting in " heart-rot." 



The different varieties of apple trees often evidenced a marked 

 variation in their relative susceptibility to the initial injury, but once 

 injured they were equally subject to the rotting of the dying parts. 



Crown-rot entails a heavy loss among most fruit growers in wind- 

 exposed regions, and whether or not the initial injuries can be 

 avoided remains to be determined. It seems possible, however, 

 that their numbers may be reduced by inducing early and moderate 

 growth in young trees, and by providing windbreaks or some device to 

 keep the trees from swaying in the wind during winter. The observa- 

 tions also suggest that high-headed or severely pruned trees are 

 more susceptible to the initial injuries. If young trees were care- 

 fully inspected in spring for evidences of loosened or cleft areas of 

 bark most of the secondary injuries and rots could be prevented by 

 carefully cutting away, at right angles to the surface, all injured bark 

 and applying grafting wax or some good tar paint to the exposed wood. 



INTRODUCTION. 



Since the publication of a critical summary of the most important 

 available papers dealing with crown-rot^ and some related subjects 

 most of the time has been devoted to a study of the disease. The 

 field observations made plainly indicate that winter-injury is the 

 first cause of the trouble; and also point to some of the predisposing 

 and environmental conditions resulting in crown-rot. But a his- 

 tological study of the initial injuries and their further development 

 during the early part of the following vegetative season was deemed 

 necessary for a better understanding of the disease. The field studies 

 are discussed in the present paper while the histological work will be 

 the basis of a subsequent report. 



The observations were continued in 1910, 1911, and 1912. Not 

 only the orchards in which the work was started but many others 

 were studied with considerable care, especially during 1910 and 1911. 

 The disease was found to vary much in different parts of the State 

 and also in different orchards of the same locality, but in general it 

 was much like that described in the above preliminary paper and 

 like that found and described by many other investigators. 



In these field studies an endeavor was made to find what environ- 

 mental conditions prevailed in and about affected orchards and which 



' Crown-rot, arsenical poisoning and winter-injury. 



N. Y. Agrl. Expt. Sta. Tech. Bui. 12:367-411. 1900. 



