496 



Jfiiinnil of A(/ricv/liire, Victoria. [10 Aug., 1917. 



Fumigation witli Carbon Dioxide. 



This is tlie most effective gas. 14.35 cubic feet of ga.s will submerge 

 one ton of grain, and can be forced in at tbe bottom of the wheat or 

 airtight silo. One pound, at atmospheric pressure, occupies a volume of 

 9 cubic feet, and would cost 3d. per lb. in large quantities. The 

 total cost would be -Ud. per ton, and the gas could be used over and over 

 again. Carbon dioxide runs to waste in distilleries. 



Drying. 



Wheat from thrashers averages C.7 per cent, to 7.2 per cent, mois- 

 ture. 



When dried in the sun this is reduced to 4.7 per cent. In 4.7 per 

 cent, and 6.7 per cent, of moisture, the weevil did not breed. With 8 per 

 cent, moisture the weevils died in six weeks without breeding. 



With 9 per cent, of moisture the weevils were dormant, and did not 

 breed, but when more moisture was added they became active and bred. 



With 10 per cent, of moisture the weevils bred, but required free air 

 in order to breed with normal rapidity. Drying the wheat artificially 

 or in the sun, and then storing in air-tight bins, is sufficient to jirevent 

 weevil from attacking it. If weevily wheat is held under the same con- 

 ditions, the weevils die oil. Moisture and a temperature of 80 deg. F., 

 without moisture, is fatal. Deprived of oxygen, all weevils die within 

 seven days. 



Certain of the above described methods are employed in breweries 

 and flour mills for ridding grain of weevils; but it is to be noted that 

 in such cases the grain is treated in bulk, and has not to be re-bagged. 



Destruction by such measures of the weevils and their eggs, when 

 they have once seriously invaded the grain, being in the case of bagged 

 wheat extremely costly, it is very important to inquire if there are any 

 means of preventing such an invasion from taking place. 



One obvious set of precautionary measures consists of measures for 

 preventing weevil from gaining access to the grain. As has been 

 already pointed out, wheat has no weevil in it when in the field*. In 

 order that weevil may not gain access to it during carriage and storage 

 it must not be packed in old bags which have become already tenanted 

 by weevils, and it must be stored in such a way that weevils will not be 

 able to reach it. Such precautions arc difficult to carry out effectively 

 in practice. 



The grain-weevils are widely distributed and are very tenacious of 

 life. Moreover, as already mentioned, a very small number gaining 

 access to stored gi-ain are able, if conditions are favorable, to multiply 

 enormously in a comparatively short time. 



Favorable and Unfavorable Conditions. 



A study of the conditions most favorable to the multiplication of 

 grain weevils, shows at once that temperature and moisture have to be 

 considered before anything else. Both of these are, of course, capable of 

 being controlled. 



The experiments of F. J. Cole, Maxwell Lefroy, and others have 

 shown that the presence of a certain degree of moisture in the grain is 

 essential to the active multiplication of the weevils. This essential 



• This does not hold good of maiit. 



