24 



BULLETIN 1313, U. S. DEPARTMENT OF AGRICULTURE 



EFFECT OF FUMIGATION ON WEEVILS IN THE PRESENCE OF GRAIN 



IN BOTTLES, BOXES, AND BARRELS 



In order to ascertain the action of the compounds as they would 

 be used in practical fumigation work, weevils were placed in pill boxes, 

 with perforations to permit the entrance of the vapor, and the boxes 

 were placed at different levels in grain, usually wheat. The weevils, 

 usually about 10 to the box, were exposed to the action of the com- 

 pounds for 24 hours, at temperatures from 21° to 32° C. 



One series of tests was carried out in large glass bottles of 19 liters 

 capacity (Table 4), another in a wooden box of 100 cubic feet 

 capacity (Table 5) , and another in a barrel of 6 cubic feet capacity 

 (Table 6) . The f umigant or mixture of f umigants was applied in all 

 these tests by pouring the calculated quantity over the top of the 

 grain and then closing the receptacle. The bottle had a stopper, the 

 barrel had a wooden head, and the box was provided with felt strip- 

 ping and a tight-fitting cover, which could be clamped down. 



(In Tables 4 and 5 the more toxic substance, with its concentra- 

 tion, is given first; the less toxic substance, used principally as a 

 diluent, with its concentration, is given next.) 



Table 6. 



-Results of fumigation tests on weevils in grain in barrels (6 cubic feet 

 capacity) 





Fumigant 



Concen- 

 tration 

 of fumi- 

 gant 



Aver- 

 age 

 mor- 

 tality 



Weevils killed after exposure for 24 hours 



Test 

 No. 



Bottom of barrel 



Middle of barrel 



Top of barrel 



S. 

 oryza 



S.gra- 

 nar- 

 ius 



Tri- 

 bol- 

 ium 



S. 

 oryza 



S.gra- 

 nar- 

 ius 



Tri- 

 bol- 

 ium 



S. 

 oryza 



S.gra- 

 nar- 

 ius 



Tri- 

 bol- 

 ium 



386 

 387 



Carbon tetrachloride 

 (75 per cent) and 

 turpentine (25 per 

 cent) . 

 do 



Los. per 

 1,000 cu. 

 ft. 

 15.0 



30.0 



7.0 

 10.0 

 10.0 

 10.0 



3.1 

 10.0 



3.1 

 10.0 



9.1 

 18.2 



1.0 

 10.0 



2.9 

 10.0 



P.ct. 



17 



14 

 52 

 87 

 71 

 100 



} 100 



| 50 



96 

 100 



} 100 

 } 92 



P.ct. 

 



30 

 100 

 100 

 100 

 100 



100 



50 



100 

 100 



100 

 50 



P.ct. 

 







P.ct. 



95 



100 

 

 100 

 100 

 100 



100 



50 



100 

 100 



100 

 100 



P.ct. 

 





 50 



100 

 25 



100 



100 







100 

 100 



100 

 100 



P.ct. 

 







P.ct. 



25 





 



100 

 



100 



100 



100 



100 

 100 



100 

 100 



P.ct. 









 100 

 100 

 100 

 100 



100 







50 

 100 



100 

 100 



P.ct. 

 







P.ct, 

 30 







394 

 409 



Carbon disulphide 



do 



60 

 



410A 

 1441 



do 



do 



100 

 100 



403 



431 



450 

 456 



/Ethylene bromide 



(Carbon tetrachloride.. 



(Ethylene bromide 



(Carbon tetrachloride. . 



Ethyl bromide 



do 



100 



100 



25 

 100 



447 

 458 



(Epiehlorohydrin 



(Carbon tetrachloride. . 



(n-Butyl nitrite 



(Carbon tetrachloride.. 



100 

 100 



1 Barrel made as tight as possible in this test. 



The insecticidal action of a gas is greatly lessened by the presence 

 of grain, probably because the grain absorbs many vapors in large 

 quantities and because the grain mechanically interferes with the 

 diffusion of the gas throughout the receptacle. For example, in a 

 glass vessel containing nothing but weevils and the vapor of the 

 compound (mixed with air), epiehlorohydrin killed 100 per cent of 

 the insects at a concentration equivalent to 0.23 pound per 1,000 

 cubic feet ; when the weevils were planted in wheat, a concentration 



