158 The Fru it-Growers Guide-Book 



Twig Blight. (See under Pear.) 



Black Rot. This is a fungus causing the decay of ap- 

 ples, quinces and pears, and has become well known, al- 

 though it is not a serious disease. Its most objectionable 

 and serious character is that it causes large cankers to 

 form on the Hmbs of the affected trees. The fruits that 

 are attacked rot quickly, but do not show the shrinking of 

 the tissues as in the case of bitter rot. After the rotting 

 has become quite well advanced the diseased area will be- 

 come quite spotted with small black specks from which 

 the spores issue. It occurs most commonly on neglected 

 and fallen fruit, and upon fruit in the storage cellar. The 

 cankers appear as deadened areas of the bark, some- 

 what shrunken and producing many little pustules from 

 which the spores arise. Removal of the cankers and thor- 

 ough spraying with bordeaux mixture gives the most com- 

 plete satisfaction, although preventive measures have not 

 been well worked out. Clean orchards are affected the 

 least. 



Crown Gall. This disease is due to an organism that 

 attacks a number of different kinds of plants, mostly of 

 the family Rosaceae, causing large swellings to form on 

 the roots or at the crown of the plant. It is exceedingly 

 troublesome in nurseries, and appears as large soft galls, 

 and may also be present as a mass of fine hairy roots. 

 In the Western states it is very troublesome as the 

 organism seems to find congenial conditions for its devel- 

 opment and distribution. The galls increase in size rapidly 

 and usually last for only one season, after which they 

 decay, only to reappear again the next season. Trees are 

 frequently so badly affected as to either die or be of little 

 value. 



No means is known of preventing the spread of the 

 disease or of destroying it after it has once entered a tree. 

 Careful inspection of nursery stock and burning all of the 

 infested trees is all that can be suggested at the present 

 time. 



"Fly Speck, Sooty Blotch. These diseases ordinarily 

 appear on the fruit from unsprayed trees, in low ground, 



