42 



less extensively tlian Paris green or London Purple, but is 

 especially excellent in destroying the currant worm. 



White Arsenic is not to be used when Paris green or Lon- 

 don purple can be had, since it is dangerous to have about 

 and is apt to burn the leaves. 



EXTERNAL POISONS. 



Pyrethrum is a powder made from the flowers of a plant 

 and is very poisonous to insects, but is perfectly harmless to 

 man and domestic animals. It kills insects by contact, and 

 can be most successfully used as a powder to be dusted by 

 means of a bellows or other powder dusting machine. Py- 

 rethrum is hard to obtain pure or at least in a fresh condi- 

 tion. It loses its strength by standing, and should be kept 

 well corked. It may be used as a spray in the proportion 

 of one pound of Pyrethrum to 40 gallons of water. Pyre- 

 thrum is very useful for killing the cabbage worm, or in- 

 sects destroying parts of plants that are ready to be eaten 

 by man. It is also of great use in clearing rooms of flies, 

 musquitoes, &c., and fleas and lice on domestic animals. 



Kerosene Emulsion is perhaps the best substance to be 

 used for sucking insects. It is made as follows : "Dissolve 

 one-half pound of hard soap in one gallon of boiling 

 water, and while the liquid is still hot, but not near a fire, 

 add two gallons of kerosene. The whole is then violently 

 churned until it forms a creamy mass, which will thicken 

 into a uniform jelly-like mass on cooling, and the oil re- 

 mains incorporated in the mass, and will not separate or 

 rise to the top. The churning can best be done by means 

 of a force pump with a small nozzle, pump the liquid back 

 into the vessel containing the liquid. The emulsion thus 

 obtained will keep indefinitely." When ready to use, thor- 

 oughly mix one part of the emulsion with nine parts cold 

 water. This is to be thrown in the form of a spray on the 

 plants, by means of some kind of a force pump and spraying 

 nozzle. (See machines.) 



The kerosene emulsion will injure no foliage, and since it 



