346 COXTROLLIXG INSECTS AND DISEASES 



gun is always to increase the drive and decrease the fineness of 

 the spray, and to hurry the operation too much. On the other 

 hand, a gun held in one position wastes material and may cause 

 injury and burning of the foliage and fruit. Burning is espe- 

 cially likely to occur on very humid, warm days when using 

 materials that are naturally quite caustic, such as concentrated 

 lime-sulfur. 



(Caterpillar Tractor Co.) 



EiG. 132. Note how the spray from the lower gun is driving through 



the tree. 



A disk nozzle may deliver an uneven spray, heaA^ier on one 

 side of the cone than on the other, or the cone may be entirely 

 hollow in the center. This may be due to a partial clogging 

 of the nozzle or to mechanical imperfections. 



In using sprays carrying coarse materials, as self-boiled 

 lime-sulfur or the wettable sulfurs, a gun will operate with less 

 clogging than a disk nozzle. 



