17 



Fig, 5. A good form of nozzle. No. 1, the complete nozzle. No. 2, 

 the nipple, unscrewed so as to show small opening for escape of 

 fluid. No. 3, the cap with wire screen at end for breaking fluid 

 into a spray. 



ience in spraying these trees about the citj^ of Washington, 

 London purple, one half pound, flour 3 quarts, water 40 

 gallons. He considers one-half to three-quarters of a 

 pound of the poison in 40 gallons (one barrel) of water 

 about the maximum strength to be used with safety. 



Insects which puncture the leaves of trees cannot be 

 destroyed with mixtures of London purple or Paris green. 

 It is true that these poisons when applied to the bodies 

 of some insects have a destructive effect, but used in 

 quantities sufficient for this purpose, they are liable to 

 injure foliage. For bark-lice, plant-lice and leaf hoppers, 

 all of which puncture and suck the sap of plants instead 

 of gnawing away and eating the substance, it is therefore 

 necessary to use other preparations. These must kill 

 when brought in contact with the body of an insect, and 

 moreover must do this without injuring the leaves. 



