540 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



tend. It particularly infests the machinery of mills, spinning a 

 web which causes flour to become felted and lumpy, and, in sum- 

 mer weather, this clogs the machinery, necessitating frequent and 

 prolonged " shut-downs " resulting in the loss, in large establish- 

 ments, of thousands of dollars. The average cash loss due to 

 closing a mill and the cost of treatment by fumigation and cleaning 

 has been estimated at about $500 for each fumigation, excluding the 

 loss to business, Avhile the owners of mills of large capacity who 

 have fumigated for this species claim a loss of $5,000 a year. One 

 prominent miller states that the loss due to stoppage while cleaning 

 is incalculable. 



The use of hydrocyanic-acid gas as a means of disinfecting mills, 

 warehouses, elevators, and other inclosures has become nearly uni- 

 versal in the principal milling centers, and especially as a remedy 

 for the flour moth. It possesses many advantages over bisulphid 

 of carbon for the same purpose, the principal ones being that the gas 

 can be generated without the aid of fire as in sulphur fumigation, and 

 that it is noninflammable and nonexplosive when generated according 

 to methods now in practice. Hence its employment in mills where 

 there might otherwise be a conflict with insurance companies. 



On account of numerous inquiries during the year (which reached 

 as high as five or six daily at times) for advice in regard to the 

 eradication of the flour moth, it was found necessary, as soon as the 

 required data could be obtained, to publish a comprehensive account 

 of the hydrocyanic-acid gas method of fumigation for the control of 

 this pest. This is published as Circular No. 112 (pp. 1-22). In 

 order to make this publication as complete as possible all of the prin- 

 cipal topics which were discussed during the year on this process of 

 fumigation were considered in detail, with the result that to date no 

 questions have been asked since its issuance that are not completely 

 answered in the publication. 



BICE MILL INVESTIGATIONS. 



By request of several rice millers, some mills in southern Texas 

 and Louisiana were investigated. In the course of these investiga- 

 tions, as well as in others conducted both in the Mississippi Valley 

 region and in the Atlantic district, it has been noticed that hydro- 

 cyanic-acid gas has one serious defect, and this has been brought out 

 especially during the year. It has very limited penetrative power 

 when used in fumigating sacks of grain and rice. Wlien used under 

 ordinary diffusion, the fact that the greater portion of both clean 

 and weevily rice is stored in sacks under ventilated sheds or in loosely 

 constructed buildings makes the problem of fumigation entirely dif- 

 ferent from that of the flour mill or grain elevator. If it could be 

 possible to apply hydrocyanic-acid gas and bisulphid of carbon with 

 pressure, as is used in sulphur fumigation by the Clayton process, 

 this problem might be solved. Otherwise it is probable that under 

 existing conditions we will have to depend upon heat as a remedy. 

 Experiments are being conducted in this direction. 



MISCELLANEOUS INVESTIGATIONS. 



The export docks of Baltimore, Philadelphia, and New York have 

 been visited and investigations have been made of the local condi- 



