FUMIGATION" AGAINST GRAIN WEEVILS 



25 



of epichlorohydrin equivalent to 2.06 pounds per 1,000 cubic feet, 

 combined with, carbon tetrachloride at the rate of 10 pounds per 

 1,000 cubic feet, did not kill all of the insects in every test. 



The compounds consistently causing 100 per cent mortality in the 

 small-scale tests in wheat (Tables 4, 5, and 6) are shown in Table 7. 



Table 7. — Most effective fumigants for weevils (based on results in Tables'4, 5, and 6) 



Test 



No. 



456 

 462 

 629 

 630 



615 

 616 



611 



612 



599 

 600 

 540 

 545 

 585 

 586 



Fumigant 



[Ethyl bromide 



\ Ethyl bromide 



/Carbon tetrachloride. 



[Ethyl bromide 



1 Carbon disulphide . - - 

 [Carbon tetrachloride. 



I Ethyl bromide 

 Carbon disulphide.- . 

 Carbon tetrachloride. 

 Ethylene bromide ... 



V Ethyl bromide 



/Ethylene bromide... 



1 Ethyl bromide 



/Methyl formate 



\ Ethyl bromide 



/Methyl formate 



Mini- 

 mum 

 concen- 

 tration 

 consist- 

 ently 

 causing 

 100 per 

 cent mor- 

 tality of 

 all species 

 after ex- 

 posure for 

 24 hours 



Lbs. per 

 1,000 

 cu.ft. 



18.2 



4.5 



10.0 

 4.5 

 2.2 



10.0 

 4.5 

 2.2 



10.0 

 5.3 



13.2 

 5.3 

 1.7 

 6.1 



11.2 

 3.5 



Test 

 No. 



603 

 604 

 631 

 632 

 589 

 590 

 594 

 597 



546 

 547 



Fumigant 



/Ethylene bromide. . . 

 \Carbon tetrachloride 



I Ethylene bromide . . . 

 Carbon tetrachloride 



\ Ethylene bromide . . . 

 /Carbon tetrachloride 

 I Ethylene bromide . . . 



[Chlorobenzene 



I Carbon tetrachloride 



/ Crotonaldehy de 



\Carbon tetrachloride 



/Ethyl formate 



(.Carbon tetrachloride 



[■Carbon disulphide... 



Mini- 

 mum 

 concen- 

 tration 

 consist- 

 ently 

 causing 

 100 per 

 cent mor- 

 tality of 

 all species 

 after ex- 

 posure for 

 24 hours 



Lbs. per 

 1,000 

 cu.ft. 

 6.2 

 10.0 



8.0 

 8.0 



5.3 

 12.0 



5.3 

 10.0 

 10.0 



2.9 

 10.0 



2.5 

 10.0 



6.4 



With the exception of carbon disulphide, the most economical 

 fumigant at 1924 prices, is the combination of ethyl formate with 

 carbon tetrachloride. (The ethyl acetate-carbon tetrachloride mix- 

 ture, 5 which was the most suitable and economical fumigant of all 

 those tested, was not tried on a small scale.) 



IN BOX CARS 



Many tests were also carried out in box cars of grain. Weevils 

 in perforated pill boxes (10 in each box) were planted at 10 different 

 levels in the grain in a box car, by putting the boxes in the compart- 

 ments of a grain sampler, which was then plunged into the gram at 

 an angle of about 45°. 



The fumigant was applied to the grain by sprinkling the liquid 

 over the surface from a small sprinkler-top watering can as quickly 

 as possible. The door of the car was then closed and sealed. 

 Twenty-four hours later the pill boxes were withdrawn and the 

 number of dead weevils was determined (Table 8). (The more toxic 

 substance, with its concentration, is given first; the less toxic sub- 

 stance, used principally as a diluent, with its concentration, is given 

 next in Table 8.) 



• The use of ethyl acetate and ethyl acetate-carbon tetrachloride mixture- was suggested by K. C. Itoark. 



