164 Principles of Plant Culture. 



the plant or its products unfit for food. The insecti- 

 cides in most general use are certain compounds of 

 arsenic (Paris green, London purple, white arsenic, 

 arsenate of lead), hellebore and pyrethum powders, to- 

 bacco, kerosene and various compounds of soda and 

 potash. With the exception of kerosene and the soda 

 and potash compounds all of these may be used either 

 as dry powder or with water. 



283. The Arsenic Compounds are effectual as insect 

 destroyers, even when largely diluted. When applied 

 in water, however, they are liable to injure foliage in 

 proportion to the amount of soluble arsenic they con- 

 tain. Wlien insoluble in water, they require stirring 

 to keep them in suspension. 



284. Paris Green (arsenite of copper), when pure, is 

 a nearly insoluble compound and may be safely used 

 upon the foliage of most plants, diluted at the rate of 

 one pound to two hundred gallons of water. For the 

 peach and nectarine it should be diluted one-half more. 

 Pure Paris green dissolves without sediment in ammo- 

 nia water. 



285. Arsenite of Lime, a very cheap arsenic com- 

 pound, may be prepared by boiling one pound of pow- 

 dered white arsenic and two pounds of fresh lime in 

 two gallons of water for twenty minutes, stirring occa- 

 sionally. For use dilute to 400 gallons. This costs only 

 one-fourth as much as Paris green. 



286. Arsenate of Lead contains less soluble arsenic 

 than Paris green and remains longer in suspension. To 

 prepare arsenate of lead* "dissolve 24 ounces of ace- 



♦ Bulletin 151, California Agricultural Experiment Station. 



