314 THE ESSENTIALS OF AGRICULTURE 



suggested the use of sprays for other insects. The cankerworm 

 and the codling moth often caused serious loss, and orchard 

 growers were greatly in need of means of control. 



As early as 1878 results were published which indicated such 

 a degree of success that numerous other experiments were 

 undertaken, and since that time many bulletins and several 

 hooks have been published on the subject. Many men have 



FIG. 156. A gasoline power-spraying machine 



spent years in experimenting with chemicals and appliances, 

 and the manufacture of spraying materials and spraying ma- 

 chinery is now an important industry. 



406. Insecticides. The potato beetle and the codling moth 

 are common insects which consume the tissue and are killed by 

 sprays containing poison (Fig. 156). In such cases compounds 

 of arsenic are most effective. Arsenate of lead and Paris green, 

 which is a combination of copper and arsenic, are cheap and 

 are generally used. Paris green acts rather more quickly, is 



