Plants as Affected by Animal Parasites. 161 



293. A Strong Decoction of Tobacco is often used for 

 destroying aphidne on plants in rooms where tobacco 

 smoke would be objectionable. The plants are immersed 

 in, or washed with the decoction. The same is often 

 effectually used on young plants of cabbage, cauliflower 

 and turnip, to prevent their destruction by the flea 

 beetle.* 



294. Kerosene is a very useful insecticide for a class 

 of insects not readily destroyed by other means (316). 

 It has generally been used as an emulsion made with 

 soap and water, for which the following formulas are 

 good. 



a Dissolve one quart of soft soap, or one-fourth 

 pound of good hard soap, in two quarts of boiling water; 

 remove from the fire, and pour into a tin can containing 

 one pint of kerosene. Agitate violently in the can for 

 three minutes. For use, dilute with an equal quantity 

 of water; or 



b Dissolve one-half pound of hard soap in one gal- 

 lon of boiling soft water; add at once two gallons of kero- 

 sene, and churn or otherwise violently agitate for five or 

 ten minutes. For use, dilute with 15 parts of soft water. 



Kerosene may also be applied in intimate mixture with 

 water, secured by pumping both liquids at once through 

 a good spraying nozzle (Fig. 70). About ten per cent 

 of kerosene should be used for most plants. 



295. Caustic Potash in solution is useful for destroying 

 certain scale insects, as the oyster-shell bark-louse, f for 

 which solutions of one-fourth pound to the gallon of 

 water may be applied during winter. 



* Phyllotreta vittata. f Mytilaspis pomorum. 



