208 STATE BOARD OF AGRICULTURE. 



to produce instant death.* This latter method is recommended, how- 

 ever, by such men as W. G. Johnson, formerly State Entomologist of 

 Maryland, and by Professor F. L. Washburn, Entomologist of the state 

 of Minnesota, who have both used it. 



The use of the gas generated by burning sulphur, for this purpose, 

 has not been tried enough times to give us much confidence in its 

 efficacy. When used at all, it should be employed at the rate of at least 

 three pounds of the sulphur to one thousand cubic feet of space inside 

 the mill, and everything about the building should be tightly closed. 

 The danger from its use is that of corroding metals and fabrics, besides 

 injuring any flour which may be present. The fumes unite with the 

 moisture from the air and produce sulphuric acid finalh^, or oil of 

 vitrol, which acts on all sorts of substances, but more especially on 

 metals. For this reason, it is necessary to have the air as dry as pos- 

 sible if the injury is to be reduced. It is hoped that some method of 

 using sulphur or something else will be perfected soon, which will be 

 just as good and safer than either the carbon-bisulphide or the hydro- 

 cyanic-acid gas. 



In an}' case, when fumigating, it is expedient to run the stock as 

 ']ow as possible to avoid exposing it to the gases, and to make it easier 

 for the gases to penetrate to all crevices, corners, etc. Hydrocyanic- 

 acid gas must be generated by means of strings or other contrivances 

 from the outside, and the several floors must be kept shut off from each 

 other when using either the hvdrocvanic-acid gas or the carbon-bisul- 

 jjhide, because of the difference in the weight between them and the air. 

 The building, in any case, must be made tight and everyone excluded 

 during the fumigation and for half a day after the building is opened 

 and ventilated. It is also necessary to open the ventilators or windows 

 from the outside, preferably by means of ropes, in order to avoid danger 

 at that time. No fires, either in the building or nearby, are admissible, 

 for the gas from carbon-bisulphide may be carried out through a crack 

 and exploded. Sulphur is apt to corrode metals, it is true, but hydro- 

 cyanic-acid gas has been known to do so to a degree. Anyone using 

 either carbon-bisulphide or hydrocyanic-acid gas should familiarize 

 himself thoroughly beforehand with all details and bear in mind that 

 he takes a good deal of responsibility upon himself in any case. 



The third method is that of chilling. Many of the pests are killed 

 by the simple expedient of opening up the mill and leaving it open for 

 about three days during zero weather. It is suggested, by Mr. F. H. 

 Chittenden, of the Bureau of Entomology, that perhaps chilling on 

 alternate days for a week might prove even better than if it were done 

 all together. This might interfere a little less with the milling opera- 

 tions, and might possibly kill more of the insects than one prolonged 

 chilling. If chilling is practical, it will be necessary to select zero 

 weather, for mere freezing will not be sufficient. Of course, all water 

 or steam pipes or receptacles must be emptied to prevent bursting. 



Finally, plenty of light and frequent and thorough cleaning will aid 

 materially in keeping the pest in check. 



*The manner of genprating and applying these gases is discussed thoroughly by W. G. Johnson in 

 his book "Fumigation Methods." 



