B. P. 1.—805. 
THE “ROUGH-BARK” DISEASE OF THE YELLOW 
NEWTOWN APPLE. 
INTRODUCTION. 
For some years plant pathologists have been familiar with a dis- 
ease of the Yellow Newtown apple tree which makes its appearance as 
a cankered or roughened condition of the bark on both trunk and 
branches. 
In the summer of 1909 the attention of the writer was called to 
this disease, which is known to growers as “‘rough bark.” So preva- 
lent is this condition of the tree in certain sections of Virginia that 
many orchardists consider it a characteristic of the variety and use 
it as a means of identification. From this fact it will be apparent 
that the disease is not only widely distributed through Yellow New- 
town orchards, but that it is sufficiently developed on individual 
trees to present a most striking appearance. 
One may find trees which show the disease not only on the young 
l-year-old wood, but also on the trunk and on all branches save 
those of the current year’s growth. In the case of old trees which 
have not been properly cared for, the roughness and the cankered 
condition of the trunk and branches are particularly striking. 
DESCRIPTION AND BEHAVIOR OF THE DISEASE. 
The first appearance of disease is to be found in the sinking of cer- 
tain definite areas of the bark, which later enlarge, turn black, and 
finally crack or break open about their margins. An examination 
of such spots shows that the underlying layer is blackened and dead. 
lt is the shriveling and subsequent warping of these dead tissues, 
coupled with the ragged margins at the points where they break off 
from the healthy bark, which bring about the typical ‘‘rough-bark”’ 
effect. Plate I and Plate Il, figure 1, showing the disease in its 
different stages, seem to justify orchardists in naming it ‘‘rough 
bark.”” The disease may continue to develop, sometimes involving 
an entire branch, or it may apparently die out and the wound heal 
over. In most cases, however, the blackened areas slowly enlarge, 
sometimes killing small branches by completely girdling them or 
leaving roughened or cankered places on the trunk or larger branches. 
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