There appear to be at least two distinct Die Back diseases, one in California, which is regarded as being due to a lack of water and other factors, and the other has been described from Missouri caused by the fungus Valsa leucostoma var. rubescens. The latter type also exists in Texas, New York and doubtless elsewhere. The California trouble is evidenced by a dying back of the branches of apricots and almonds. The middle-western and eastern disease shows as cankers on the southwest side of trees. In this connection sun-scald, or late winter injury, is suggested; and it is not unlikely that temperatures do play a part in bringing about the disease. Large branches die, which is a symptom that may cause some confusion in an attempt to distinguish the two Die Back diseases. Where Valsa leucostoma var. rubescens is a factor, its pycnidia show as whitish dots over the surface of the lesion.
(See in this connection Frost Injury under Apple, page 35, and Die Back under Peach, page 299.)