200 OHIO EXPERIMENT STATION: BULLETIN 332 



insect under treatment. Some insects will succumb to weak soap 

 solutions, while others require heavier doses. Most plant lice, how- 

 ever, are rarely able to withstand a bath of 



Soap 1 pound 



Water 5 to 8 gallons 



Care must be taken, of course, in the spraying of tender grow- 

 ing plants not to make the solution too strong. The greatest field 

 of usefulness for the soap solutions is in the treatment of plant lice. 



Kerosene emulsion. — As with the soap solutions, kerosene emul- 

 sion is not so generally used at present as it has been in the past. 

 Until the beginning of the last decade, however, it was the stand- 

 ard remedy for plant lice and similar insects. It is still recognized as 

 an effective insecticide, and its decline in popularity has been due to 

 the inconvenience and labor involved in its preparation. The stock 

 emulsion is prepared as follows: 



Soap (laundry or whale oil chipped) V2 pound 



Kerosene (coal oil) 2 gallons 



Water (preferably soft) 1 gallon 



Dissolve the soap in the full amount of water and when this 

 solution is boiling hot, remove from the fire and add the kerosene. 

 Immediately and in the most violent manner possible agitate the 

 mixture, one of the most satisfactory methods being to perform the 

 mixing in a dasher churn, using the dasher for the agitating instru- 

 ment. As a result of the agitation the soap solution and the oil 

 emulsify, forming a white, creamy mass from which the oil does not 

 separate. Ordinarily 5 minutes agitation will bring the desired 

 result. 



After the agitation is complete the resulting mixture is termed 

 the stock emulsion. It is then ready for use, though it may be 

 stored for some time if not immediately needed. For controlling 

 plant lice and pests of a similar nature, the stock emulsion is diluted 

 with 15 to 20 parts of water. Soft water is better than hard for 

 this purpose. 



Care should be taken in the use of kerosene emulsion to have 

 the oil completely emulsified; otherwise the floating, free oil will 

 cause severe burning if sprayed upon the foliage of plants, some- 

 times even proving fatal to the entire plant structure. Because 

 of this chance defect in the emulsion either through improper pre- 

 paration or through deterioration, and because burning may result 

 also by insufficient dilution, kerosene emulsion is generally con- 

 sidered somewhat treacherous. Whenever possible, therefore, a 

 safer and equally effective treatment is employed. 



