﻿42 



BULLETIN 1357, U, S. DEPARTMENT OF AGRICULTURE 



Table 17. — Results of plot experiments witTi paradichloro'bensene against larvae 

 and pupce of the strawberry rootioorm 









Nnmber of 













Number of 













larvae and 













larvee and 









Period 



Num- 



pupae 





Aver- 





Period 



Num- 



pupse 





Aver- 



Dos- 



after 

 treat- 



ber 

 of 



Con- 

 trol 



age 



Dos- 



after 

 treat- 



ber 

 of 



Con- 

 trol 



age 









age 











ment 



plants 



Exam- 

 ined 



Dead 





trol 





ment 



plants 



Exam- 

 ined 



Dead 





trol 













Per 



Per 













Per 



Per 



Ounce 



Bays 









cent 



cent 



Ounce 



Days 









cent 



cent 



0.2... . 



6 



2 



10 



6 



60.0 



}■ 45.9 



0.4-.. . 



6 



2 



15 



9 



60.0 



1 



0.2.„. 



10 



3 



27 



11 



40.7 



0.4... . 



7 



7 



35 



32 



91.4 



[ 88.8 



0.25... 



5 



5 



69 



53 



76.8 



1 



O.4.... 



9 



7 



20 



. 20 



100.0 



0.25... 



10 



5 



27 



24 



88.9 



}■ 80.5 



O.4.... 



10 



3 



19 



18 



94.7 



1 



0.25... 



14 



5 



22 



18 



81.8 



1 



0.5..-. 



5 



3 



19 



16 



84.2 





0.3.... 



6 



2 



20 



5 



25.0 



1 



O.5.... 



6 



2 



15 



8 



53.3 



[ 79.2 



O.3.... 



7 



7 



24 



22 



91.7 



[ 76.3 



0.5.... 



10 



6 



31 



25 



80.6 



O.3.... 



9 



7 



25 



23 



92.0 



0.5..-. 



13 



4 



12 



12 



100.0 



J 



0.3...- 



10 



3 



28 



24 



85.7 



1 



O.6.... 



6 



2 



10 



8 



80.0 



1 92.9 



0.375.. 



5 



5 



32 



25 



78.1 



1 



0.6..- 



10 



3 



18 



18 



100.0 



0.375.- 



10 



5 



39 



35 



89.7 



> 85.2 

















0.375- 



13 



5 



10 



9 



90.0 



J 

















To determine plant tolerance of paradichlorobenzene it was also 

 applied to plants in five plots which were receiving the regular cul- 

 tural treatment accorded roses. The crystals were placed around the 

 base of the plant and covered with soil. At the end of 10 days to two 

 weeks they were removed from some plants but were left around 

 the others until vaporized. The results were not satisfactory in 

 either case. Even in the cases where the crystals had been removed 

 and the lowest strength — one-fourth ounce per plant — was used, the 

 bushes gradually declined in vigor and eventually died. 



SODItTM CYANIDE 



Sodium cyanide in solution was tried during the season of 1920, 

 but sufficient data on the mortality of the larvae and pupse were not 

 obtained at that time. Pronounced stimulation of root growth, with 

 a corresponding increase in terminal growth, had been observed 

 repeatedly to result from light dosages of this material. This treat- 

 ment would therefore be desirable because of its stimulating effect 

 on the plants, provided it was also effective in killing the soil stages 

 of this insect. 



Table 18. — Effects of sodium cyanide in solution on larvce and pupw of the 

 strawberry rootworm in pot experiments 









Condition 5 days after treatment 



Amount of sodium 

 cyanide in one- 

 half pint water 





Larvae 



Pupae 





Larvae 



Pupae 



Dead 



Alive 



Missing 



Control 



Dead 



Alive 



Missing 



Control 



Grams 

 0.45 



20 

 20 

 20 

 20 



10 

 10 

 10 

 10 



17 

 17 

 18 

 20 





 

 

 



3 

 3 

 2 

 



Per cent 

 85 

 85 

 90 

 100 



8 

 6 

 10 

 9 





 

 

 1 



2 

 4 

 

 



Per cent 

 80 



0.89 



60 



1.33. . 



100 



1.77 



90 







