CHAPTER XXV 

 PRINCIPLES OF SPRAYING 



Too few who need to spray know the principles of spraying. It 

 is necessary that the grower know what to spray for, and what and 

 ffhen to spray (Fig. 211). There are several purposes in view 

 when a spraying compaign is conducted. (1) To prevent disease, 

 (2) to fight insects which suck juices of plants. (3) to kill insects 

 which eat the leaves or other tissues of the plants. The materials 



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Fig. 211. — For spraying apple orchards lime-sulfur and arsenate of lead (shown above) 

 are better than Bordeaux mixture and arsenate of lead, (shown below). Upper and lower 

 lots each from a tree sprayed three times. (Illinois Station.) 



used for these three purposes are of different character. One 

 should not be used for the other, but sometimes the poison sprays ' 

 for chewing or eating insects may be combined with the materials 

 used to prevent disease. 



Spraying pays in dollars. The best orchardists spray intelligently. 

 They spray for definite purposes, with suitable materials at proper 

 times. Spraying will then improve the quality of the product and 

 increase the yield. This is true of both fruits and vegetable 

 crops (Fig. 212). 



Spray Materials to Prevent Disease. — Nearly all of the plant 

 diseases are caused by fungous growth. A few, however, are from 



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