CONTROL Of THE HOP APHIS. 33 



but it is very desirable to have a large tank wagon made expressly 

 for this purpose. When low spray tanks are used the spray can be 

 run from the supply tank by gravity, but in most cases it is necessary 

 to employ a good pump. 



EXCHANGE TANKS. 



When conducting spraying operations it is desirable to keep the 

 entire force constantly employed. The use of an exchange tank is 

 one of the best methods for accomplishing this purpose. An extra 

 machine is filled after the other machines have started and is 

 exchanged for the first one emptied. The exchange tank is driven 

 down the row in which the nearly empty tank is working. When 

 empty the men move back and take the exchange tank, the empty 

 tank being then refilled and exchanged for the next empty tank. 



SPRAY RODS. 



When the hops are growing upon short poles the spray is most 

 readily applied with a short spray rod. In the trellised yards, how- 

 ever, the hops are much taller and a 10-foot rod is necessary. The 

 aphides are mostly upon the underside of the leaves, and in order to 

 wash them thoroughly the spray must be directed from below. 

 When angle nozzles are not available the spray rod may be bent so 

 that the spray is readily directed to the underside of the leaves. If 

 one or the other of these methods is not employed the material will 

 not be satisfactorily applied. 



NOZZLES. 



By exercising great care it was found possible to spray the hop- 

 vines thoroughly with a nozzle that produced a very fine mist spray. 

 It was found much easier, however, to do the same work with a nozzle 

 that produced a slightly coarser washing or driving spray. This 

 type of spray is more satisfactory because by its driving force it 

 turns the foliage and dashes over it. When cheap labor is employed 

 good work is more readily obtained with the coarse driving spray 

 than with the very fine mist spray. 



THE COMPRESSED-AIR SPRAYING MACHINE. 



The compressed-air spraying machine (PL IX, fig. 1), which is 

 described below, was invented by Mr. Theodor Eder, of Perkins, Cal., 

 who by the following statement has generously dedicated it to the 

 use of the public. 1 



Whereas, I, Theodor Eder, of the town of Perkins, county of Sacramento, and 

 State of California, having invented certain improvements in spraying devices for 



1 A copy of this patent (No. 1046572) may be obtained for 5 cents by addressing the Commissioner of 

 Patents, Washington, D. C. 



