78 THE SAX JOSE OE CHIXESE SCALE. 



enouo'li to wet the bark, and should not. to anv extent, at least, run 

 down the trunk. The collection of water and oil about the trunk is 

 just as dangerous to the tree as is that of the pure oil. 



In the use of the oil sprays noted above one who has not had expe- 

 rience with them is advised to make some careful preliminary tests to 

 fully master the process, preferabh' waiting two or three weeks to 

 determine the results before entering on the general treatment of the 

 orchard. It is well, also, with the oil-water mixtures, to test the pump 

 from time to time, spra^nng into a glass jar or bottle to determine b}^ 

 actual measurement whether the correct percentages of oil and water 

 are being maintained. 



peteoleu:m-soap emulsions. 



The kerosene-soap emulsion, following chief!}' the Riley-Hubbard 

 formula, has been one of the standard means against scale insects for 

 twenty years. The distillate emulsion generally employed in Cali- 

 fornia for spraying citrus trees, oq which the lime, sulfur, and salt 

 wash can not be used, is substantially the same thing, except that it 

 is made with the California distillate or petroleum oil, Crude petro- 

 leum of any kind, as well as the refined product, mav also be used in 

 making this emulsion. The use of the soap emulsions against the San 

 Jose scale in the East has not been verv o-eneral, on account of the 

 greater facility with which the pure oil or oil-water mixtures can be 

 applied. The difficulty of obtaining uniform results with the latter 

 has led to a return to the use of emulsions to some extent, and there 

 can be no doubt about their superior merit when it is desired to dilute 

 the pure oils. Emulsions may be applied at any strength with abso- 

 lute confidence that there will be no variation. Where the emulsion 

 can be prepared wholesale by steam power its employment is attended 

 w^ith no difficulties. In California it is prepared by oil companies and 

 sold at very slightly more than the cost of the oil and soap ingredi- 

 ents. It is made after the following formula: 



Petroleum gallons. . 2 



Whale-oil soap (or 1 quart soft soap) pound. . ^ 



Water (soft) gallon. . 1 



The soap, first finely divided, is dissolved in the water bv boiling and 

 immediatelv added boilino- hot, awav from the tire, to the oil. The 

 whole mixture is then agitated violently while hot by being pumped 

 back upon itself with a force pump and direct-discharge nozzle throw- 

 ing a strong stream, preferablv one-eighth inch in diameter. After 

 from three to five minutes' pumping the emulsion should be perfect, 

 and the mixture will have increased from one-third to one-half in 

 bulk and assumed the consistence' of cream. Well made, the emulsion 

 will keep indefinitely and should be diluted onl}- as wanted for use. 



