EMULSIONS FOE JAPANESE BEETLE 



13 



the tangled root mass, but is appreciable in the aggregate. Experi- 

 mental work has shown that it is much easier to kill the larvae in iris 

 roots than in peony roots because of the difference in the distribution 

 of the soil. Here, again, soil-absorption is apparently the limiting 

 factor. A larva in the center of a cubic inch of soil is not affected to 

 nearly the same extent by the dip as a larva in the center of a mass of 

 soil and roots consisting of 1 cubic inch of soil mixed with 3 cubic 

 inches of roots, when both are submerged in the same concentration of 

 dip. In fact, the submergence of iris roots for 15 hours in a dip con- 

 taining 0.5 cubic contimeter of ascaridole per 3 liters of water at 70° F 

 completely killed the larvae in them; whereas twice this dosage was 

 required for killing the larvae in peony roots under the same conditions 

 of time and temperature. Incidentally the peonies were not injured 

 by a dip of this greater 

 strength when submerged 

 for the time stated, but the 

 added cost of the dip, while 

 not prohibitive, led the 

 writers to experiment with 

 other toxic materials in 

 emulsion as a control for 

 the larvae infesting this 

 particular plant. Of the 

 materials tested in this con- 

 nection carbon disulphide 

 was found to be the most 

 feasible. 



CARBON-DISULFIDE 

 EMULSIONS 



' EMULSION 1 



Experimental work 

 showed that carbon disul- 

 fide could be emulsified by 

 soaps in general, and the 

 writers found the old style 

 rosin-fishoil soap to be the 

 best for this purpose. It 

 is a thick, heavy soap and 

 must be heated with water to dissolve it. When it is available a 

 stock soap solution can be made by adding 12.5 grams of rosin-fishoil 

 soap to 87.5 cubic centimeters of water, heating until dissolved and 

 allowing the solution to cool. Add 20 cubic centimeters of this stock 

 solution to 50 cubic centimeters of carbon disulfide in an Erlenmever 

 flask and agitate until the ingredients emulsify, which will require 

 but a few minutes. Larger quantities, using the same proportions, 

 may be emulsified with a butter churn or ice-cream freezer. The 

 emulsion proper is white and has the consistency of thick cream. 

 When added to water it disperses evenly and remains indefinitely in 

 suspension. 



EMULSION 2 



Where fclie old style rosin-fishoil soap is not available a good 

 emulsion may !><■ made by mixing 0.5 cuDic centimeter of oleic acid 



Fig. 2. — Peony root, divided longitudinally, showing infesta- 

 tion by larvse of the Japanese beetle 



