36 INSECTS INJURIOUS TO VEGETABLES 



CONTACT POISONS 



Kerosene emulsion is the standard remedy for sucking 

 insects such as aphides or plant-lice, plant-bugs and the like, 

 and is of value against other soft-bodied insects, which cannot 

 for different reasons be safely poisoned by Paris green and 

 similar insecticides. The best form for ordinary use is the 

 kerosene-soap emulsion, made by combining 2 gallons of kero- 

 sene, Yz pound of whale-oil soap, or i quart of soft soap with 

 I gallon of water. 



The soap should be dissolved in boiling water and then poured 

 while boiling (away from the fire) into the kerosene. The 

 mixture is then churned violently for about five minutes by 

 means of a force-pump and direct-discharge nozzle throwing 

 a strong stream by pumping the liquid back upon itself. At the 

 end of this time the mixture will have become of the con- 

 sistency of thick cream. Properly prepared an emulsion will 

 keep almost indefinitely, and should be diluted only as needed 

 for use. For most insects, except scales, the staple emulsion 

 should be diluted with from 15 to 20 parts of water. A 10 per 

 cent, solution, or even stronger, is sometimes necessary. 



In the preparation of kerosene emulsion a force-pump is a 

 necessity, since, if not made according to directions, a perfect 

 emulsion is not formed. There is then danger of injury to the 

 plants by the kerosene, as also useless waste. There is also 

 danger and waste if the insecticide is not applied by means of 

 a fine nozzle in the form of a spray, which should be fine and 

 mist-like. It should be sprayed only long enough to cover the 

 plants and not so that the liquid forms into globules and 

 runs off. 



In the practical application of this insecticide certain setbacks 

 are frequently encountered. One of these is due to the fact 

 that aphides and many other sucking insects feed more or less 

 exclusively on the under surface of leaves, which necessitates 



