EMULSIONS FOE JAPANESE BEETLE 17 



When plants infested with larvae are immersed in the worniseed- 

 oil dip, it has been found that longer periods of submergence are 

 required to insure complete larval mortality. This is due to the fact 

 that the soil present in the roots absorbs to a certain extent the toxic 

 material, thereby slowing up its action upon the larvae. As a result 

 of the research here described it is recommended that Japanese iris 

 and sedum be immersed for 15 hours, and perennial phlox for from 

 9 to 18 hours, the time depending on the amount of soil present in 

 the roots. These periods of dipping provide ample margins of safety 

 over the time actually required to obtain mortality of the larvae 

 under these conditions, while the plants concerned are unaffected by 

 the treatment. 



Carbon disulfide. — In the case of peony roots it has been found 

 advisable from the standpoint of cost to use a carbon disulfide 

 emulsion dip. The plants should be immersed for a period of 15 

 hours in a dip the concentration of which is equal to 0.5 cubic centi- 

 meter of carbon disulfide (emulsified) to 1 liter of water. The 

 same limitations of temperature apply in the use of this material 

 as in the case of the oil of wormseed. 



Commercial experience with these emulsions in 1922 and 1923, 

 involving the treatment of 45,000 plants of this nature, valued at 

 $10,000, indicate that when applied under Government supervision 

 the method is satisfactory to the quarantine officials and to the 

 nurserymen from the standpoint of cost and the safety of the plants. 



LITERATURE CITED 



(1) Clayton, W. 



1923. The theory of emulsions and emulsification. London. 160 pp. 



(2) Henry, T. A., and Paget, H. 



1921. Chenopodium oil. In Jour. Chem. Soc. (London), vol. 119. pp. 

 1714-1724. 



(3) Leach, B. R., and Thomson, J. W. 



1921. Experiments in the treatment of balled earth about the roots of 

 coniferous plants for the control of Japanese beetle larvse. In Soil Sci., 

 vol. 12, pp. 43-61. 



(4) Nelson, E. K. 



1920. The composition of oil of chenopodium from various sources. In 

 Jour. Amer. Chem. Soc, vol. 42, pp. 1204-1208. 



(5) 



1921. A rapid assay method for the determination of ascaridole in oil of 

 chenopodium. In Jour. Amer. Pharm. Assoc, vol. 10, pp. 836-837. 



(6) Russell, G. A. 



1922. The influence of methods of distillation on the commercial value of 

 oil of American wormseed. In Jour. Amer. Pharm. Assoc, vol. 11, pp. 

 255-262. 



(7) Thomas, A. W. i 



1920. A review of the literature of emulsions. In Jour. Indus, and Engin. 

 Chem., vol. 12, pp. 177-181. 



