FUMIGATION AGAINST GRAIN WEEVILS 39 



3 out of 15 chlorides tested; the only iodide tested; 1 alcohol out of 

 8 alcohols and phenols tested; 3 out of 4 aldehydes tested; 2 out of 



4 ketones tested; both of the chlorine-substituted ketones tested; 1 

 of the 2 chlorohydrins tested; 5 out of 9 esters tested; 4 out of 12 

 sulphur compounds tested; 1 nitrile out of 5 nitriles and isonitriles 

 tested; both of the nitrites tested; 2 out of 8 amines tested; and 

 pyridine. 



The relative toxicity of the different classes of compounds can 

 not be given because the low volatility of several of those tested 

 gave only very low vapor concentrations. As a class, the hydro- 

 carbons showed the lowest insecticidal efficiency, not one of the eight 

 tested equaling carbon disulphide in fumigating power. The most 

 effective fumigant in the glass-jar tests was epichlorohydrin, which 

 killed the rice weevil at a concentration of 0.09 per cent, equivalent 

 to 0.23 pound per 1,000 cubic feet. It was, however, an unsatisfactory 

 fumigant in the presence of grain. 



There is no constant relationship between the boiling points and 

 the lethal concentrations of the compounds killing 100 per cent of 

 the rice weevils after exposure for 24 hours. 



A much greater concentration of fumigant is required to kill 

 weevils in wheat than to kill those exposed directly to the vapors 

 in glass jars. A still higher concentration is necessary to kill weevils 

 in wheat in box cars. Ethyl formate and ethyl acetate were the 

 only promising f umigants for grain in box cars. The acetate, however, 

 costs only about one-third as much as the formate. 



Odoriferous constituents of low volatility from commercial grades 

 of ethyl acetate (both the 85 per cent and the 99 per cent grades) 

 are carried through from the fumigated wheat to the flour, and 

 even to the bread baked from it. A pure grade of ethyl acetate, 

 however, leaves practically no odor in the fumigated grain or in the 

 bran or shorts made from the grain, and none in the flour or in the 

 bread baked from the flour. 



The insecticidal efficiency of ethyl acetate under practical fumigat- 

 ing conditions is increased by the addition of carbon tetrachloride. 



The most effective fumigant, other than carbon disulphide, 

 against weevils in wheat, in grain cars, under practical fumigating 

 conditions, is a mixture of about 40 volumes of ethyl acetate and 

 about 60 volumes of carbon tetrachloride. It is noninflammable at 

 ordinary temperatures. The proper dosage of this mixture for 

 fumigating box cars is about 45 pounds per 1,000 cubic feet. Both 

 the ethyl acetate and the carbon tetrachloride must be tested to make 

 sure that they are free from odoriferous constituents of low volatility 

 before they are used in grain fumigating. 



LITERATURE CITED 



(1) Altson, A. M. 



Beetles damaging seasoned timber— IV. Methods of treatment. In 

 Timber Trades Journal (1922), S/:1170-l. 



(2) Bertrand, Gabriel, and Rosenblatt, M. 



Action toxique compared de quelques substances volatiles sur divers 

 insectes. In Compt. rend. (1919), 168: 911-13. 



(3) Burmeister, Hermann. 



A manual of entomology, translated bv W. E. Shuckard, London (1836), 

 p. 391. 



(4) Carteret, M., and Carteret, G. 



Sur l'alte>ation des farines et cdreales par SO,. In Bull. soc. chim. 

 (1909;, series 4, vol. 5, p. 270-2. 



