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49 BULLETIN 1357, U. S. DEPARTMENT OF AGRICULTURE 
TABLE 17.—Resulis of plot experiments with paradichlorobenzene against larve : 
and pupe of the strawberry rootworm 
fy umber of | Danes of 
Period} Num- see Aver- Period| Num- apa ne Aver- 
Dos- | after | ber | Con- age Dos- | after | ber Con- | age 
age er igh : Ste Sea ol abrOl con age Lent ¢ ‘ SET es rel ou 
ment | plants) 5. .m- .| tro ment | plants|5.4m- tro 
ined Dead aed Dead 
| Per Per Redvees Per | Per 
Ounce| Days cent cent Ounce | Days cent cent 
Q:22" 6 Z 10 6 | 60.0 \ 45.9 (0 Ye. eae 6 2 15 9; 60.0 
Oe 10 3 27 | 11 | 40.7 > O:42 = 7 7 35 32 | 91.4 88.8 
Q225 oe 5 5 69 53 | 76.8 (Ae 9 7 20 20 ;} 100.0 : 
Qf2naas 10 5 27) | 24 | 88.9 80.5 |} 0.4..--| 10 3 19 18 | 94.7 
Of25e== 14 5 22 18 81.8 Q:58252 5 3 19 16 | 84.2 
0.32258 6 2 20 5 25. 0 Orb 6 2, 15 8 53. 3 79.2 
Ore Pes 7 7 24 22 91.7 76.3 Qs: 222 10 6 31 25} 80.6 c 
Sha 9 7 25 23 | 92.0 ; (Ropes 13 4 12 12 | 100.0 
0325 10 3 28 24 | 85.7 6 6 2 10 8 | 80.0 \ 92. 9 
OS 75s 5 5 32 250) aiSe O:6222. 10 3 18 18 | 100.0 
0.375__ 10 5 39 35 | 89.7 85. 2 
0:375_- 13 5 10 9} 90.0 ‘ | 
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. 
SODIUM CYANIDE 
Sodium cyanide in solution was tried during the season of 1920, 
but sufficient data on the mortality of the larve and pupz 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.—Hffects of sodium cyanide in solution on larve and pupe of the 
strawberry rootworm in pot experiments 
Condition 5 days after treatment 
Amount of sodium | Number of— : 
cyanide in one- Larve Pups 
half pint water - 
| 
| 
Larve | Pupz | Dead | Alive |Missing/ Control) Dead | Alive Missing Control 
Grams Per cent | Per cent 
PCS ee AR Re NO 20 10 17 0 3 | 85 8 0 a 80 
PRG EE SaaS 20 10 17 0 3 | 85 6 0 4 60 
(Se Se ea 20 10 18 0 2} 90 10 0 0} 100 
TDi A ape i a a 20 10 20 0 0) 9 1 0 90 
100 
