864 Summary of Agricultural Experiments, [jan., 



(i.e., each plot of the same variety, or each plot receiving the same 

 manurial treatment, &c.) should consist of five sub-plots, each of one- 

 fortieth of an acre, systematically distributed over the area under 

 observation. 



Destruction of Field Mice (Praktische Blatter fur Pflanzenbau und 

 Pflanzenschutz, September-October, 191 1). — An account has already 

 been given in this Journal (January, 191 1, p. 861) of the havoc wrought 

 by a serious plague of field mice which occurred in Bavaria in 1910. 

 A report by the Royal Agricultural and Botanical Institute at Munich 

 urges upon agriculturists the necessity of taking active measures against 

 mice before the plague becomes so serious as to render the success 

 of remedial measures doubtful. 



The experience gained in combating the plague in 19 10 went to show 

 that all the methods adopted have their advantages and disadvantages, 

 and that conditions which are favourable to the employment of one 

 method are unsuitable for the employment of another. 



With regard to preventive measures, the best method recommended 

 for general use against field mice is fumigation with carbon bisulphide. 

 Old pieces of sacking should be dipped in the liquid and pushed as 

 far as possible into the burrow with a stick, and the gas given off 

 asphyxiates the mice. A method, however, that does the work more 

 economically, quickly, and completely, besides eliminating all danger 

 to the operator, is to use an apparatus specially invented for the pur- 

 pose and sold throughout Germany. Where carbon bisulphide is 

 employed without apparatus, great care has to be exercised on account 

 of its inflammability, and it must be stored so that the proximity 

 of any burning or smouldering material is impossible. 



An older method than the above consists in laying poisons in drains 

 or in wooden boxes open at the sides, covered with straw, and placed 

 in the fields. The renewal of the poison from time to time prevents 

 any increase in the numbers of field mice. 



The foregoing preventive measures can be carried out by the indi- 

 vidual, but when an extensive plague of field mice occurs, combined 

 action only can be expected to meet with success. Rat poisons and 

 viruses seem to be preferred where combined action is necessary, 

 especially the former, on account of their simplicity and the rapidity 

 with which they take effect. Apart from their dearness, however, all 

 poisons have the disadvantage that they are liable to be eaten by 

 animals other than mice, and care must therefore be taken that 

 domestic animals, or wild animals which destroy mice, do not get 

 at the poison. Corn poisoned with strychnine is mostly used, but 

 phosphorus is also often employed. In the latter case straws are 

 smeared with the preparation and thrust into the burrows. The mice 

 in passing out rub against the straw and die through licking the 

 poison from their bodies. Barium salts, especially barium carbonate, 

 have proved very effective, and have the additional merit of being 

 cheap. 



Rat virus is recommended where measures are to be adopted on a 

 large scale for the destruction of field mice. The most favourable 

 time to use the virus is in the early spring, as the mice are then 

 least resistant to the bacilli, and in the absence of other food are 

 :ompelled to eat that which has been treated with the virus. Virus 



