DIAGNOSIS OF THE CANKER DISEASE OF APRICOT TREES CAUSED BY EUTYPA ARMENIACAE HANSF. AND CARTER

For those who are not familiar with the disease, it is most easily observed in the summer season, after the fruit is harvested. At this time, one may find that the leaves on one branch (large or small) of a tree have suddenly wilted and become dry. These dead leaves will remain attached to the affected branch after the normal time of leaf-fall and commonly throughout the following winter season. After the dead branch has become dry, it may be broken off very easily »like a carrot«: branches which are killed by other pathogens usually do not exhibit these features.

An examination of the lower part of the wilted or dead branch will reveal a canker adjacent to some previous injury (usually a pruning wound which has exposed the xylem. The bark will usually be depressed and darkened, there may be some longitudinal cracks and often (but not always) there may be some exudation of gum from the internal tissues. By contrast, a canker caused by bacteria (Pseudomonas spp.) is usually confined to the bark tissues only.