CONTACT INSECTICIDES 21 



and household plants. Soft soap should be used 

 twice as strong. 



Whale-oil soap is more commonly used. One 

 should always procure a potash soap. It costs 3 

 to 6 cents per pound. Use i pound to 5 or 6 gal- 

 lons of water for summer application. In winter, 

 for scale, use 2 pounds to i gallon. Whale-oil soaps 

 vary greatly in their water content and are liable 

 to contain free potash thus causing burning. Fish- 

 oil soap can be made easily and cheaply at home. 

 The composition may be known and the free potash 

 avoided. 



Formula for home-made fish-oil soap 



45 



Caustic soda 6 lbs. or i>^ lbs. 



Water i>^ gals. or i>4 qts. 



Fish-oil 22 lbs. sV^ lbs. 



Dissolve the caustic soda in the water. After 

 the soda is dissolved, add the fish-oil gradually, in 

 the meantime stirring the mixture thoroughly and 

 vigorously. Complete and thorough stirring while 

 the oil is being slowly poured into the water and 

 soda is absolutely necessary. Use i pound to 6 or 7 

 gallons of water. 



Fish-oil may be purchased of N. B. Cook Oil Co., 

 New York. 



Oils 



Mineral oils are much used for contact insecti- 

 cides, usually in some form of an emulsion that is 

 miscible with water. They are particularly val- 

 uable against aphids, and scale insects. 



Kerosene emulsion "^^ — Kerosene may be emul- 

 sified with milk or soap, the latter being now most 

 universally used. 



Formula for kerosene emulsion : 



45 Van Slyke & Urner— N. Y. State Expt. Stat., Bull. 257. 



