300 MANUAL OF FRUIT DISEASES 



then pinkish here and there. If the injured spots are left 

 untreated, bark-beetles and fungi frequently follow the work 

 of the frost. The most common fungus in this connection 

 is Valsa leucostoma var. cincta (see page 301). In the past, 

 orchards, which probably would have recovered if proper 

 treatment had been given, have been cut down. If the 

 bark clings tightly or is only partly loosened, the trees may 

 recover. Moderate pruning back, removing not more than 

 one-third to one-half of the previous year's growth, good 

 cultivation, and moderate fertilization is regarded as a good 

 course to pursue. See more detailed discussion of frost-injury, 

 its nature and treatment, under Apple, page 35. 



DIE-BACK 



Caused by Valsa leucostoma Fr. var. cincta Rolfs 



The first important notice of this disease in the United States 

 dates back about fifteen years. It is a condition more or less 

 common to cherry and peach-trees in old neglected orchards, 

 particularly in central and eastern America. The trouble also 

 prevails in Germany and Australia. A similar disease caused by 

 a closely related variety of the causal fungus affects the plum. 



Some varieties of peaches are said to be injured more than 

 others, although none is free from die-back. It is thought 

 that the varying local conditions are responsible for such dif- 

 ferences in more cases than can be attributed to varietal suscep- 

 tibility. Affected twigs and branches are killed back; even 

 large limbs are often severely injured. 



Symptoms. 



The pathogene attacks only the woody portions of the tree. 

 Rough black cankers, sometimes large affected areas, appear 

 on limbs. This condition is popularly referred to as sun-scald. 

 The lesions center about a bud or a wound. At times there is 



