INSECTICIDES AND EQUIPMENT FOR CONTROLLING INSECTS 405 
The barrel pump.—This type of sprayer has a hand-operated pump 
attached to a barrel or similar container for the spray. The assembled 
outfit is mounted on a sled or wheels (fig. 5) or loaded in a wagon 
or truck. In certain types, called wheelbarrow sprayers, the container 
is small enough so that it is mounted between handles with a single 
wheel in front and is pushed by the operator. 
Figure 5.—Barrel pump mounted on wheels and equipped with hose, extension 
rod, shut-off, and nozzle. 
Depending upon the size of the outfit, the barrel sprayer is fairly 
satisfactory for spraying commercial plantings of truck, fruit, nurs- 
ery, or other crops. However, the operation of the pump is laborious, 
and it is difficult to maintain constant high pressure. Because of these 
facts a power outfit is to be preferred. 
Traction sprayers.—This type of sprayer is usually mounted on two 
wheels. Essentially it consists of a tank, with a pump geared to the 
wheels and with the nozzles usually attached to a fixed boom (fig. 6). 
Ordinarily these machines are horse-drawn. Pressures reaching as 
high as 125 to 250 pounds per square inch can be maintained, provided 
that the rig is in constant motion. 
Machines of this type were designed for spraying field crops, includ- 
ing potatoes and tomatoes and small fruits, where it is not necessary 
to make any stops, as is the case when spraying trees. For the most 
part traction sprayers have been replaced by power machines, the 
latter being much more satisfactory. 
Power sprayers.—These machines are so called because the pumps 
are driven by motors, either gasoline or electric. They range in size 
from small 10- to 50-gallon tank-capacity outfits, with single-cylinder 
pumps which maintain a pressure of 150 to 200 pounds, to large rigs 
