FUNGOUS AND PHYSIOLOGICAL DISEASES. 487 



young and old, suffer alike, and a few trees have been 

 found affected which were still standing in the nursery 

 rows. Very often, little notice is taken of it, and it gradu- 

 ally works its way, nipping off the new growth, and the 

 trees, in consequence, make very little progress. Years of 

 work and much capital are often wasted in mistaken efforts 

 to bring a grove into healthy condition. 



The disease is easily recognized. The young twigs 

 die back several inches. Irregular, reddish-brown ele- 

 vations, at first closed, later cracked open and filled with 

 a resinous substance, make their appearance on the small 

 branches and twigs. These vary greatly in length, height 

 and shape. Often elevated pustules, filled with a gummy 

 substance, occur on the young growth. These seem, in 

 some cases, at least, to develop into open ruptures. Ad- 

 ventitious buds are frequently produced, and those which 

 are not smothered by the resinous exudation develop, 

 thus giving rise to several branches from a single node. 

 Sometimes the only noticeable mark of the disorder on a 

 branch is the presence of a resinous knot in the axils of 

 the leaves, where the buds should be. Slightly affected 

 branches have often a dark, greasy appearance. The 

 small growth is usually twisted and bent. On the fruit 

 the disease is manifested by the-presence of dark, brown- 

 ish blotches and by cracking or splitting. Many fruits 

 drop off. As the disease advances the trees try in vain to 

 throw out new branches. Symptoms become more strongly 

 marked, the tips of the bare, distorted branches protrude 

 above the dark-green foliage. Gradually the larger 

 branches are embraced, water-sprouts develop only to be- 

 come affected and die. Eventually the tree succumbs. 



Die-back is not a fungous disease, no spores nor fun- 

 gal threads having been found connected with it as causal 



