350 The Principles of Fruit-growing. 



leaf, or even the entire plant, or a large part of 

 it, shows a general weakening and disease, as if 

 there were some cutting off of the accustomed 

 source of nourishment. Such diseases are very likely 

 to be seen in a general yellowing and death of the 

 leaf, in the dying of the leaf along the main veins 

 and around the edges, showing that the difficulty is 

 one which affects the entire leaf, and not any par- 

 ticular part of it. In general, there is a tendency 

 for the foliage in plants so attacked to wither up 

 and hang on the tree for a time. The peach yel- 

 lows and pear blight are diseases of this kind. 

 There are no specific treatments for troubles of this 

 sort. They must be approached by what physicians 

 call prophylaxis, that is, by methods of sanitation 

 and prevention. The diseased plants or parts are 

 cut away and burned. All those conditions which 

 seem to favor the development of the disease are 

 removed. Varieties which are particularly susceptible 

 are discarded. Careful management in matters of 

 this sort is often much more important than any 

 attempt at specific treatment. 



Before taking up a discussion of spraying, it 

 may be said that the best treatment for borers and 

 similar pests is to watch the plants carefully, and 

 to dig the insects out at least twice every year. 

 In grounds which are kept in clean tillage, such 

 insects are rarely as troublesome as they are in 

 neglected areas. This is both because the insects 

 find places of lodgment in neglected orchards, and 

 because the fruit-grower is so seldom present that 



