372 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



DIE-BACK. 



The most conspicuous disease or trouble affecting walnuts in southern 

 California is that characterized by this name. Two general types of die- 



FIG. 90. Die-Back, caused by dry soil and cold weather. 



back may be distinguished, one on old trees, particularly hard shells, 

 which die back slowly all over the top, and another occurring suddenly 

 during a single winter in all or part of the limbs, which may die back 



