119 



A Comparison' of Oils for Oil Emulsion 



Good emulsions were made with all grades of oil used, but five of 

 them show a somewhat too high percent of live scale in the fall tests. 

 Comparing the scale kill with the analyses of oils, it will be found that 

 the most effective oils fall within certain limits. After a conference with 

 government entomologists who had been working on the control of San 

 [ose scale with oil emulsions at Bentonville, Arkansas, and at Vincennes. 

 Indiana, and with the Entomologist of the Purdue Agricultural Ex- 

 periment Station, a joint statement was issued in the fall of 1924 to the 

 effect that the best results had been obtained with oils within the following 

 limits : 



Specific gravity 87 to .93 at 20° C. 



Volatility Not above 2% at 110° 



C. for 4 hours. 

 (Saybolt test.) 



Viscosity 90 to 250 seconds at 



100° F. (Saybolt 

 test.) 



A Comparison of Boiled Fisii-oil-Soap Ejiulsioxs 

 AND Cold-mixed Emulsions 



1. Scale Kill 



Table X, summarizes all the tests made in the Hartline orchard with 

 boiled fish-oil-soap emulsions of 2% strengths and all those with cold- 

 mixed emulsions except where lime sulfur was combined with them. 

 This table shows the cold-mixed emulsions to be not quite so effective 

 as the boiled emulsions. This table, however, gives only a rough com- 

 parison of all types of cold-mixed emulsions used with certain types 

 of boiled emulsion. 



2. C old-mixed Oil Emulsions 



The argument in favor of cold-mixed emulsions is the ease with 

 which they can be made. They do not require boiling, nor handling while 

 hot, and they can usually be more cheaply made than a boiled soap emul- 

 sion. In most cases they do not have as high a wetting power as the 

 soap emulsions, and this makes them much less eft'ective against certain 

 kinds of insects, such as aphids. 



