CHAPTER XI 

 INSECT AND DISEASE CONTROL 



From the standpoint of control, both insects and diseases 

 naturally divide into two groups : (1) those that can be 

 controlled by spraying; and (2) those that require some 

 other method of attack. A sub-group might be made in 

 the latter which would include those for which no remedy 

 is known other than the complete eradication and destruc- 

 tion of the affected trees. 



The insects that fall into the first group must also be 

 considered from the standpoint of their methods of feeding. 

 If they eat parts of the tree or fruit, they are to be sprayed 

 with an arsenical poison. If they suck the juices of the 

 tree or fruit, they are unaffected by poisons applied to the 

 exterior parts of the tree ; hence a substance must be used 

 in spraying that kills the insects by coming in contact with 

 them. 



The poison now most largely used in spraying peaches 

 is arsenate of lead. Arsenate of lime (calcium arsenate) is 

 sometimes used instead of arsenate of lead, but is not advised 

 for peaches and other stone-fruits. The contact insecticides 

 most often used are the concentrated lime-sulfur preparations, 

 miscible oils, and to some extent nicotine extracts of tobacco 

 which are effective against certain aphids or plant-lice. These 

 lime-sulfur mixtures are also effective in the control of certain 

 diseases that can be reached during the dormant condition. 



218 



