320 PRINCIPLES OF ECONOMIC ENTOMOLOGY 



The standard formula for kerosene emulsion is as follows: 



Hard soap | pound 



Hot water (soft) 1 gallon 



Kerosene (coal oil) 2 gallons 



To form the emulsion take a gallon of soft water and 

 dissolve in it a half-pound of soap, then remove from fire, 

 add two gallons of kerosene, which should be thoroughly 

 mixed and agitated at once. One of the best methods is to 

 run the solution through a spray pump, driving it back into 

 the bucket from which the solution is drawn, and about 

 five or six minutes of this mixing will produce a perfect emul- 

 sion. It should be carried to such completion that there 

 will be no tendency for the oil to separate. Small quantities 

 may be made rapidly in the proper proportions by ihe use of 

 an egg-beater or by a process which produces a violent 

 agitation w^hich may be maintained for some length of time. 

 This strong emulsion should be kept in a cool place and 

 covered or in a tight receptacle and may be diluted as wanted 

 with soft w^ater, the amount of dilution depending upon the 

 insects to be reached. For scale insects, one pint of strong 

 emulsion to nine parts water. Soft plant lice are readily 

 killed by a solution of one part of stock solution to fifteen 

 parts of water. 



Tobacco Extract.— This is a very efficient contact insecti- 

 cide and may be used against many kinds of insects but 

 especially such forms as plant lice, thrips, and the better- 

 protected sucking insects. Various solutions are on the 

 market but the one termed Black Leaf 40, containing 40 

 per cent, nicotine sulphate, is one which seems to have 

 proved one of the best; this is used in dilutions of 1 part 

 to 300 of water to 1 part to 600 parts of water — for use in 

 winter time, when plants are dormant, and for summer use, 

 dilutions — 1 to 500, to 1 to 1000 are recommended for tender 

 insects such as plant lice. Similar solutions may be used for 

 parasitic lice and mites on domestic animals. 



Tobacco dust may be used or an extract prepared from 

 this by steeping or soaking in water overnight. In making 

 the preparation boil one pound of dust or stems to a gallon 



