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. 
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, Hg. 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 
