324 CONTROLLING INSECTS AND DISEASES 



placing these disks frequently. A fine driving spray that 

 spreads into a cone as it comes from the nozzle and goes on to 

 the fruit and foliage in small globules, rather than one that 

 washes the tree, is the objective. The Virginia Experiment 

 Station found that, at 300 pounds pressure and using arsenate 

 of lead, outer spray disk openings of Yiq and i^^ch wore in 

 about 45 hours of continuous spraying to 1/12 and Yiq inch^ 

 respectively. It would seem then that the outer disks should 



be changed after one week 

 of use. 



The shape of the spray 

 is determined in the eddy 

 chamber, the space between 

 the inner and outer disks, 

 created by the insertion of 

 a washer or gasket from % 

 to %e inch thick The outer 

 disk has a single opening 

 in center. The inner disk, 

 usually much thicker, has 

 from two to six holes driven 

 through at an angle, near 

 the outer circumference. 

 The deeper the eddy cham- 

 ber and the straighter the 

 holes in the inner disk, the 

 narrower the cone of. spray 

 and the greater its driving quality. The spray of greatest fine- 

 ness is obtained by a shallow eddy chamber, a decided slant 

 to the holes through the inner disk, and a small aperture in 

 the outer disk, but its driving or carrying power is reduced. 

 Nozzles with six holes in the inner disk, and with a spray 

 apperture of Yiq to 1/12 i^^ch, have proved very satisfactory 

 and throw the spray much farther than nozzles with but two 

 holes in the disk. 



Disk nozzles have capacities ranging from % to 2% gal- 



{Yirginm Exp. JSta.) 



Fig. 117. Nozzles with six holes in the 

 disk are favored by some growers. At 

 the left the whirl disk and nozzle base 

 are in one piece ; at the right the whirl 

 disk is removable from the nozzle base. 



