312 CONTROLLING INSECTS AND DISEASES 



applications or holding it as an insurance and safety factor 

 against the time of need. 



(gf) Consider the Important Mechanical Features of Spray'^ 

 ers and Equipment, Spray machines are known as power, 

 traction^ or hand machines, depending on the source of the 

 power for their operation. The commercial grower is primarily 

 interested in the power outfit, the term applied to engine- 

 operated machines. Such outfits are well standardized, and 

 many good ones are on the market. They provide a high pres- 



{Bardie Mfg. Co.) pectcd of it with a rcservc 

 Fig. 104. A two-cyclinder pump. left over. A machine oper- 

 ated to the full limit of its 

 capabilities is subjected to great strain and goes to pieces sooner 

 than more powerful machines operating with an ample reserve. 

 The capacity of a sprayer is the number of gallons per minute 

 that the pump will deliver at a stated pressure, usually 600 

 pounds. ]\Iany manufacturers overrate the capacity of their 

 machines under actual orchard conditions. Many growers, on 

 the other hand, habitually run their pumps with an overload 

 that materially reduces their period of service. Allowance must 

 be made for the capacity losses due to worn valve seats and cyl- 

 inder packing, small leaks, and other minor defects in opera- 



sure when desired, a uni- 

 form pressure throughout the 

 spraying operation, and a 

 capacity ranging from the 

 small one-cylinder outfits to 

 the giant-powered machines 

 used for forest, street, and 

 park spraying. 



1. The Pump. The spray 

 machine can be no better 

 than its pump. Pump ca- 

 pacity is important. It 

 should be great enough so 

 that it may do the job ex- 



