306 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE. 



heavy cylinders; trampling it by cavalry or by droves of sheep; 

 liberating large numbers of cats; and injecting water, steam, or suffo- 

 cating gases into the mouse burrows. Many measures practicable 

 on a small scale or of value in the early stages are entirely inade- 

 quate for the suppression of well-established plagues, particularly 

 where farms are as large as in the United States. Among such 

 methods are digging trenches or pitfalls wider at the bottom than 

 at the top, into which the mice fall ; killing by means of traps, clubs, 

 or dogs; burning off the herbage in infested areas; and flooding the 

 fields. The elimination of these leaves as methods generally ap- 

 plicable for suppressing plagues only two — the employment of dis- 

 ease and poisoning. 



DISEASE. 



The employment of bacterial diseases fatal to rodents has been a 

 subject of considerable research and experimentation. It is evident 

 that a disease which Avill quickly spread from one mouse to another, 

 without endangering other animals, is exceedingly desirable. While 

 epidemics of disease have been frequently considered a prime cause 

 of the abatement of plagues, it has not yet been demonstrated that 

 such epidemics can be artificially produced. Dr. Loeffler's experi- 

 ments in destroying field mice in Thessal}^ in 1892-93 by means of 

 the Bacillus typhimurium were reported as completely successful, 

 but now it appears questionable whether these results did more than 

 synchronize with the natural abatement of the plague. Experiments 

 in Russia in 1894 with the similar organism isolated by Meresch- 

 kovski were also reported as successful; and in France, in 1904, the 

 Danysz virus is said to have proved in a measure efficacious. 



Attempts by ranchmen to produce epidemic disease among the mice 

 in Humboldt Valley by means of advertised bacterial preparations 

 failed. Although we admit that, when properl}^ distributed and 

 fresh, these organisms are fatal to those mice which eat them, yet on 

 this basis they are still far too expensive for general employment. 



POISONING. 



Poisoning is the most generally applicable, cheapest, and most 

 certain means for controlling mouse plagues at present known. 

 Poison preparations, however, must possess, in addition to effective- 

 ness, the least possible danger to man, to domestic stock, and to valu- 

 able wild birds and mammals. The following recommendations are 

 based on extensive experiments and practice during the mouse plague 

 in Nevada, and are applicable to similar species of mice elsewhere. 

 Phosphorus, on account of its extremely dangerous character, the 

 limited number of baits on which it can be used, and its destructive- 



