254 EXPERIMENTAL FARMS 



4 GEORGE V., A. 1914 



cessful employment as a fungicide. Sulphate of iron (copperas 1 ), as our experiments 

 have shown, has a very low fungicidal power compared with that of bluestone (sul- 

 phate of copper). Consequently, we may conclude that its value for this purpose 

 practically depends upon its bluestone content, which the analysis shows to be 25 

 per cent. 



POTASSIUM CYANIDE. 



This chemical is used for the production of hydrocyanic (prussic) acid used in 

 tbe fumigation of nursery stock, greenhouses, etc. Commercial grades nowadays 

 usually contain large percentages of sodium cyanide or, indeed, they may be entirely 

 sodium cyanide. This in itself is no disadvantage, but rather the reverse, since 

 weight for weight, the sodium compound will disengage a larger amount of hydro- 

 cyanic gas than will the potassium salts. Certain low-grade cyanides, however, are 

 on the market and these will be more or less ineffective unless used in larger quantities 

 than called for by formula. It will be, therefore, for the purchaser when ordering tc 

 stipulate the high-grade cyanide (98 per cent to 100 per cent) and further, if possible, 

 to obtain it in unopened containers as put up by the wholesale druggist. The latter 

 precaution is advisable by reason of the readiness with which this compound deterior- 

 ates when exposed to the air. In a bottle of cyanide kept loosely corked for some 

 months and examined in the farm laboratories it was found that the lumps at the 

 top had lost nearly two-thirds of their strength. Several samples of cyanide bought 

 from bulk were analyzed and were found to a greater or less degree below the guar- 

 anteed strength, but those obtained in original and sealed containers conformed with 

 ■ he guarantee. 



Owing to the extremely poisonous character of cyanide and of the hydrocyanic 

 >cid gas, which it so readily evolves, the very greatest care must be exercised in 

 handling this material or in conducting a fumigation. The work should be performed 

 by responsible and experienced persons. 



GOPHER POISON. 



The more common poison used to-day in the northwestern provinces for the 

 destruction of gophers, is strychnine, though from our own experiments at Indian 

 Head, Sask., and that of the Wyoming Experiment Station, carbon bisulphide is 

 probably a more effective exterminator of these pests. 



Carbon bisulphide is a highly inflammable liquid, with a very disagreeable smell. 

 Though not corrosive, its vapor is detrimental to health when breathed in quantities, 

 it, however, can be used without danger provided ordinary care is exercised — more 

 especially in regard to flame and fire. The method of use is to saturate a small ball of 

 rags or cotton waste with the bisulphide and thrust it into the fresh burrow in the 

 -veiling, closing the mouth of the burrow with a little earth. Dry balls of horse 

 manure have been used successfully instead of cotton waste. The fumes from the 

 bisulphide are very heavy and sink down the burrow or tunnel, destroying the gophers 

 by suffocation. 



Strychnine is dangerous to live stock running loose and, moreover, it is difficult 

 at times, when food is plentiful, to get the gophers to eat the poisoned grain. Strych- 

 nine is intensely bitter even in very dilute solutions and no doubt the gophers are 

 often deterred from eating the grain by tasting the poison on the outside of wheat. 

 For this reason, the poisoned wheat, while still damp, might be sprinkled with a little 



sugar. 



In gopher-infested districts, solutions of strychnine are frequently distributed 

 by municipalities to farmers, a certain strength or number of grains of strychnine 

 per fluid ounce being stipulated. A number of such solutions have been forwarded 



