2IO THE APPLE 



Unscrupulous nurserymen may cut away these galls if they 

 appear on the roots, and sell the trees. But since the cutting 

 away of the affected roots does not always eradicate the disease, 

 the best practice is to discard all affected trees. 



Root rot {Clitocybe parasitica). Where stumps and roots of 

 trees have been left in the soil previous to the planting of apple 

 trees, it has been noticed that the roots of the latter have been 

 attacked by a mushroomlike growth. The mycelium, or root sys- 

 tem, of this mushroom penetrates the root system of the apple 

 tree and causes the death of both roots and tree. This disease 

 often occurs, however, without the presence of old stumps and 

 roots. It has been particularly troublesome in Oklahoma, Missouri, 

 and other Middle Western and Southern states. 



The means of controlling this disease seem to be simple. Dig- 

 ging up and burning the trees is the most practical, although 

 trenching the affected trees is sometimes practiced. 



Diseases affecting the Woody Parts of the Tree 

 Aboveground 



Pear blight (Bacillus amylovorus). This is a serious disease of 

 the apple, as well as of the pear. All varieties of the apple seem 

 less resistant to this disease than the pears, nearly all being 

 affected somewhat. 



This disease is more commonly noticed just after pollination. 

 Generally, during the four weeks after the fruit has "set," the 

 tips of the branches, and often the blossoms, become wilted, turn 

 black, and subsequently die. The bacillus as a rule does not pene- 

 trate far into the older wood of the apple tree ; it injures chiefly 

 the tips of the branches, producing the so-called "tip blight." 



When first attacked, the soft bark appears water-soaked, then 

 slowly changes in color until it is shriveled and black. Sometimes 

 there is apparent a sharp line of demarcation between the diseased 

 part of the twig and the healthy part, denoting that the organism 

 has ceased to spread. Often the affected bark tissue is ruptured 

 and a gelatinous substance, the result of the work of the bacillus, 

 is exuded. This gelatinous matter is not always of the same color, 

 but varies from milky white to black. 



