FUMIGATION OF FKUIT TO DESTROY JAPANESE BEETLE 



21 



100 



80 - 



g 60 



Tests were also run with 4 ounces each of compounds nos. 3 and 4 

 per 1,000 cubic feet at 75° and 70° F. Both compounds gave a com- 

 plete larval mortality with an exposure of 45 minutes. 



While all four of the materials being tested produce hydrocyanic 

 acid, two important factors help to account for the varying results 

 obtained with them, viz, the amount of hydrocyanic acid derivable 

 from each material and the rapidity with which the gas is released 

 from each. 



The theoretical production of hydrocyanic acid from 1 pound of 

 100-percent pure calcium cyanide is 266.2 grams (0.587 pound). 

 Therefore, from 1 pound of compound no. 1, assuming a 45-percent 

 calcium cyanide content (based on the manufacturer's claim of 40-50 

 percent) the theoretical production would be 119.8 grams (0.264 

 pound) of hydrocyanic acid. From 1 pound of compound no. 2, 

 assuming an 88-percent calcium 

 cyanide content (50-percent 

 cyanogen), the theoretical pro- 

 duction would be 234.3 grams 

 (0.517 pound) of hydrocyanic 

 acid. With compounds nos. 3 

 and 4, however, the theoretical 

 production of hydrocyanic acid 

 from a " 1-pound can " should 

 be 453.6 grams (1 pound), since, 

 as indicated above, the weight 

 designation on the cans indicated 

 the net weight of the hydro- 

 cyanic acid. 



From compounds 1 and 2 the 

 gas is released by the action of 

 atmospheric moisture, whereas 

 from compounds 3 and 4 it is re- 

 leased by volatilization. The 

 difference in the rapidity of the 

 release of the gas by these two 

 methods is very evident if data 

 in table 3 are compared. One 

 pound of crude calcium cyanide 

 (compound no. 1) should theo- 

 retically produce 0.264 pound of 

 hydrocyanic acid, as shown in the preceding paragraph, while a " 4- 

 ounce can " of compound no. 4 should produce 0.25 pound. While the 

 theoretical production of hydrocyanic acid in these two cases is prac- 

 tically identical, it will be seen that with a 15-minute exposure in the 

 first case only 33 percent of the larvae were killed, while in the second 

 99 percent were killed. It is evident that in the second case the hydro- 

 cyanic acid volatilized rapidly and that during the period of exposure 

 the larvae were subjected to a higher concentration than that to which 

 the larvae were subjected in the first case. That this explanation is 

 not merely theoretical can be seen by comparing the mortalities 

 which 4 ounces and 1 pound of compound no. 1 produced in the same 

 length of time. In 45 minutes, for example, the 4-ounce dosage 

 killed 56 percent of the larvae while the 1-pound dosage killed 100 

 percent. Since the compound and the method of liberation were 



40 



20 



15 30 45 



TIME OF FUMIGATION (MINUTES) 



C0MP0UND{l[] 2§ 3(H 4§] 



Figure 16. — -Mortality of Japanesebeetle larvae 

 after exposure to compounds nos. 1 to 4 (16 

 ounces per 1.000 cubic feet) at 80° F. 



