CHAPTER VIII 



THE PRINCIPLES AND PRACTICE OF SPRAYING 



THE SPRAYING of fruit trees In the 

 United States is of comparatively recent 

 origin, having been a general commer- 

 cial practice for less than two decades. It In- 

 volves the principle of applying with force and 

 In the form of a fine rain or mist, water In which 

 a poison or a substance which kills by contact 

 is suspended. The first application of the prin- 

 ciple was against chewing insects with hellebore. 

 Pure arsenic was early used and soon led to 

 the use of other arsenicals. 



Our greatest fungicide, Bordeaux mixture, 

 was discovered by accident In 1882 when It was 

 found to control mildew In France. Up until 

 about five years ago Bordeaux mixture as the 

 fungicide and parls green as the poison were 

 almost universally used. Within the last few 

 years, however, there have been developed two 

 substitutes which, although known and used to 

 some extent for twenty years, have only re- 

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