EMULSIONS FOK JAPANESE BEETLE 17 
When plants infested with larvse are immersed in the wormseed- 
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 larva?. 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 larva 1 
under these conditions, while the plants concerned arc 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 larvae. 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. 
1920. A review of the literature of emulsions. In Jour. Indus, and Engin. 
Chem., vol. 12, pp. 177-181. 
