ENTOMOLOGY. 379 



THE LIME-SULPHUR WASH. 



Composition and Preparation. In the matter of composition 

 of the wash, scarcely any two experimenters agree. Salt was a part 

 of the original composition of the sheep dip and has long been re- 

 tained, with the idea that it added, perhaps, to the caustic qualities, 

 and particularly to the adhesiveness of the wash. For the latter 

 purpose a very small amount only, 1 or 2 pounds to the bushel 

 of lime, need be added, following the custom in the preparation of 

 whitewash mixtures. In practical experience, however, the salt seems 

 to have been of very little benefit and is therefore omitted in the 

 formula now given. The proportion of lime and sulphur is a 

 matter of some indifference. The mixture obtained is sulphide of 

 lime, and if an excess of lime is used it simply remains undissolved 

 in the mixture and adds to the whitewashing character of the appli- 

 cation. Too much lime is distinctly objectionable, however, because 

 of the greater difficulty of spraying and harder wear on the pump 

 and nozzles. The formula here given is substantially the one which 

 has been hitherto recommended by this Bureau, reduced to the 45 

 or 50 gallon basis, or the capacity of the ordinary kerosene barrel 

 commonly used in its preparation by the steam method. 



Unslaked lime pounds. . 20 



Flowers or flour of sulphur do. ... 15 



Water to make gallons . . 45 to 50 



The flowers of sulphur, although requiring somewhat longer 

 cooking, seems to make a better wash than ground sulphur, but the 

 latter may be employed. Stone lime of good quality should be se- 

 cured and slaked in a small quantity of water, say one-third the 

 full dilution. The sulphur, previously mixed up into a stiff paste, 

 should be added at once to the slaking lime. The whole mixture 

 should be boiled for at least one hour, either in an iron kettle over 

 a fire out of doors or in barrels by steam. Prolonged boiling in- 

 creases the percentage of the higher sulphides, but the practical 

 end is obtained by boiling for the time indicated. In the process 

 of making, the color changes from yellow to the clear brown of sul- 

 phide of lime, except for the excess of lime floating in it. After 

 an hour's boiling the full quantity of cold water can be added, and 

 the mixture should then be promptly applied in order to get its full 

 strength before the higher sulphides are lost by cooling and crystal- 

 lizing out. In transferring to the spray tank it should be passed 

 through an iron screen or strainer, and the tank itself should be pro- 

 vided with an effective agitator. 



Directions for Use. The wash is a winter application where 

 used as an insecticide. It may be applied at any time after the 

 falling of foliage in early winter and prior to the swelling of the 

 buds in spring. The later the application can be made the better 

 the results, and the best period is just before the buds swell in March 

 or April. It will probably be necessary also to make this applica- 

 tion every year, or at least as often as the San Jose scale develops in 

 any numoers. The wash kills the San Jose scale not only by direct 

 caustic action, but also by leaving the limy coating on the trees, 



