EMULSIONS FOR JAPANESE BEETLE 
Table 6. — Comparative toxicity of four fractions of wormseed oil 1 * 
Properties at 25° C. 
Percentage of larvae 
killed by immersion in 
dip for hours specified 
Fraction 
Specific 
gravity 
IN) 
Solution 
in 70 per 
cent 
alcohol 
Solution 
in 60 
per cent 
acetic 
acid 
5 
6 
7 
8 
12 
100 
100 
100 
100 
24 
First 
0.858 
0.950 
1.0024 
1. 0181 
—Strong. 
-8. 73° 
-2. 41° 
-2.53° 
1. 4805 
1.4760 
1.4720 
1. 4780 
None 
6.5 vols 
1.4 vols 
0.5 vol 
Per cent 
8 
62.5 
100 
97 
50 
100 
100 
75 
75 
100 
100 
100 
25 
75 
100 
75 
100 
100 
100 
75 
100 
Second 
100 
Third (ascaridole frac- 
tion) 
100 
Fourth (residue)... 
100 
1 Temperature of dip in each case, 70° F. (21° C). The larvae were immersed for the specified number 
of hours in the dip prepared from the fraction tested, and the percentage of those killed is tabulated. A 
total of about 300 larvae were used in these tests. 
APPLICATION TO LARV.E IN SOIL AND PLANTS 
The results given in Table 4 indicate the action of wormseed-oil 
emulsion dip upon the larvae when the latter are removed from their 
habitat (the soil) and dipped. The larvae are killed in six hours at a 
temperature of 70° F. When, however, the soil containing larvae or 
infested plants (such as iris or phlox) is dipped in the material, it 
must be submerged for a longer period in order to kill all the larvae 
present. The soil itself apparently absorbs the toxic material from 
the dip and interferes to some extent with the insecticidal action of 
the material upon the larvae. This phenomenon of soil absorption 
and its relations to the use of soil insecticides has been discussed at 
considerable length in a previous paper by Leach and Thomson (5, 
p. 58), and summarized as follows: 
Dipping tests indicate that certain compounds in solution, capable of produc- 
ing a gas insoluble or only slightly soluble in water, are toxic to Popillia larvae. 
These compounds may be divided into two classes: (1). Compounds slightly 
soluble in water, e. g.," carbon disulphide, thymol, mustard oil, etc. (2). com- 
pounds readily soluble in water, such as sodium sulphocarbonate and sodium 
ethyl xanthate. These compounds in solution, on being decomposed by organic 
acids, yield carbon disulphide, the active killing agent. 
Saturated solutions of compounds in class 1 (about 1 to 1,000) readily kill 
Popillia larvae when the latter are removed from the soil and dipped in the 
solution for a definite period of time. However, when Popillia larvae are 
embedded in a soil-ball and the latter dipped in these solutions the grubs con- 
tained within the soil-ball remain unharmed. Soil adsorption, or, in other words, 
physical "locking up" of the compound in solution by the moisture film surround- 
ing the minute soil particles, is the apparent reason for the failure of these relatively 
dilute solutions to function in soil. That portion of the compound adsorbed by 
the soil is apparently rendered impotent as far as its ability to produce larval 
mortality in the soil is concerned. 
Compounds of class 2, when used in dilute solutions give results comparable to 
those obtained by the use of compounds in class 1. However, when compounds 
of class 2 are employed in relatively concentrated solutions, a. quantity of the 
compound sufficient to produce 100 per cent mortality of Popillia larvae remains 
free in the soil after the soil particles have adsorbed the compound to the limit 
of their capacity. 
However, in the treatment of such plants as Japanese iris, phlox, 
and sedum, the limitation above noted does not preclude success in 
killing the larvae present in the root mass, for, while some soil is 
31469°— 25f 2 
