288 INSECTS 



more dangerous to the trees than the undiluted oil 

 itself. Nevertheless, kerosene emulsion shares with 

 whale oil soap the burden of the fight against plant lice, 

 with the advantage of cost in favor of the emulsion. 



A more recent development in the use of petroleum 

 oils is found in the miscible or "soluble" oils, sold 

 under special names such as "Scalecide," " Kill-O- 

 Scale," "San-U-Zay," or simply as "soluble petro- 

 leum." These are preparations of petroleum, crude or 

 partly refined, so combined with vegetable or animal 

 oils, rosin oil and sulphonated oil, as to be readily 

 miscible in water to any extent, forming a perfectly 

 homogeneous spraying mixture of even effectiveness 

 throughout. None of these oils contain over 75 per 

 cent, actual petroleum and few contain over 10 per 

 cent, of water, which is actually necessary to form the 

 emulsion. They are, therefore, approximately equal 

 in their effect and are extremely useful as winter washes 

 against scales hibernating in the partly grown condi- 

 tion. Against the pernicious or San Jose scale a dilu- 

 tion with fifteen parts of water is the weakest mixture 

 that should be used in general practice. Good results 

 have been obtained with a solution of 20 to i, under 

 exceptional circumstances; but I would rather recom- 

 mend a dilution of only twelve times if I were anxious 

 to secure definite effects. These oils have no vaseline 

 or paraffin e residue, hence can be safely applied for 

 successive years, even peach showing no appreciable 

 injury within my experience. It is on large old apple 

 and pear trees that these miscible oils find their most 

 effective field of use, for they spread and penetrate 

 well and when applied with proper force can be made 

 to reach wherever a scale can go. This quality makes 

 them effective against such species as the pear psylla, 

 which hibernate as adults in crevices and under rough 



