EMULSIONS FOR JAPANESE BEETLE 7 



TOXICITY OF WORMSEED-OIL EMULSIONS 



The dip made with emulsion of oil of wormseed was tested in three 

 different ways: (1) Larvae, free from soil, were submerged in the dip 

 for varying periods to determine the time necessary to kill them at 

 various temperatures. (2) A similar series of exposures was made with 

 larvae embedded in soil. (3) Plants infested with the larvae were 

 immersed in the dip under varied conditions of temperature and 

 length of exposure to determine the toxicity of the material to the 

 larvae under natural conditions and the resistance of the plants to the 

 insecticide. The entire crop of one of the local nurseries was treated 

 in this test, which was carried out under commercial conditions. 



TOXICITY OF WORMSEED OIL TO JAPANESE BEETLE LARV.E 



The toxicity of the emulsions of wormseed oil to the larvae of the 

 Japanese beetle was determined by submerging the larvae, free from 

 soil, in the dip for varying periods of time at various temperatures. 

 Emulsion 1 as listed in Table 2, and emulsions 3A and 9A of Table 3, 

 were employed in these tests in the proportions of 1 cubic centimeter 

 of ascaridole to 6 liters of water. The wormseed oil employed assayed 

 75 per cent ascaridole by the acetic acid method already described. 

 The results of these tests are presented in Table 4. It will be ob- 

 served that the best results were obtained when the temperature of 

 the dip was maintained at 65° or 70° F. Lower temperatures reduced 

 the toxicity of the material. 



Tab le 4. — Toxicity of wormseed-oil emulsions to Japanese beetle larvse (not in soil) 1 



Temperature 



Percentage of larvse killed by immersion in dip for hours specified 



of dip 



3 



4 



5 



6 



7 



8 



9 



12 



15 



18 



21 



24 



° F. 

 50 



° C. 



10 

 16 

 18 

 21 









50 

 75 

 100 

 100 







75 

 100 

 100 

 100 



75 

 100 

 100 

 100 



75 

 100 

 100 



100 

 100 



100 

 100 



100 



60 





 25 

 











100 



65 



50 



50 



25 



75 



100 

 100 



100 

 100 





70 



















1 A total of 500 larvae were used in the tests on which this table is based. In each instance here recorded 

 the larvae were immersed for the specific time, and the percentage of those killed is tabulated. In each 

 case the dip contained ascaridole in the proportion of 1 cubic centimeter to 6 liters of water. 



TOXIC STABILITY OF WORMSEED-OEL EMULSION 



In the course of the experimental work several samples of the 

 emulsion of various ages accumulated. These were tested under 

 identical conditions and all on the same day in order to determine 

 whether the stock emulsion on standing had undergone any change 

 which might affect its toxicity. The results of these tests are given 

 in Table 5. It will be observed that the emulsion did not decrease 

 in toxicity within the space of 40 days. The results indicate that the 

 toxicity will persist indefinitely if the emulsion is kept in a cool 

 place, since the chemical change, if any, is slow. 



