72 JOURNAL OF ECONOMIC ENTOMOLOOY [Vol. 15 



Arsenate of lime is unsafe when used straight, or in combination 

 with dusting sulphur, on apple, and other tender foliage. With these 

 exceptions arsenate of lime is either equal or superior to lead hydrogen 

 arsenate for the ordinary uses to which that poison is put. 



There has been a great deal of controversy as to the comparative 

 values of lead hydrogen arsenate and arsenate of lime in ILme sulphur 

 solution. Different experimenters have reported results that are at 

 variance, yet I have no doubt but that all of the results were fairly 

 reported. From our experience backed by chemical investigations, 

 differences in the time that elapses between the adding of the poison 

 and the application of the spray and differences in climatic conditions 

 may throw the advantage as regards arsenical injury either way. If 

 the spray is applied immediately the poison is added, lead arsenate will 

 usually prove the safer. Weather that will cause the spray to dry 

 rapidly also gives an advantage to lead arsenate. Over a period of 

 years, arsenate of lime has given us a slightly safer combination with 

 lim.e sulphur than lead arsenate. A small quantity of excess lime 

 makes both somewhat safer in a lime sulphur solution. In using arsenate 

 of lead, the greatest safety is obtained by adding about two pounds of 

 hydrated lime to one pound of dry arsenate of lead in water before 

 adding to the lime sulphur solution. In using arsenate of lime, two or 

 three pounds of hydrated lime s.hould be used to each pound of the 

 arsenate of lime. Both may be dimiped directly into the lime sulphur 

 solution. 



One of the places where arsenate of lime is superior to all other arsenic- 

 als now on the market, is in the alkali sulphide and poly -sulphide 

 solutions. In Nova vScotia, a large proportion of the apple growers 

 have, since they abandoned lime sulphur, used a sodium poly-sulphide 

 solution for the calyx spray. There we worked out the following 

 formula which has proved highly successful under Nova Scotian con- 

 ditions:- — One pound soluble sulphur or one quart sulfocide, one-half 

 potind arsenate of lime and five pounds of hydrated lime to each 40 

 Imperial (50 wine or U. S.) gallons of water. Increasing the amount of 

 arsenate of lime by one-half in this formula, is safe under most conditions. 



In all types of Bordeaux mixture, we have found arsenate of lime 

 safe, efficient and very convenient. While white arsenic may be used 

 in Bordeaux mixture at a still lower cost, it is questionable if small 

 growers or those who have to trust the mixing of their spray chemicals 

 to poor types of labor, can find an arsenical that would in any way 

 be more satisfactory than arsenate of lime. 



In Nova Scotia, about two-thirds of the arsenate of lime used on 

 apples is applied in copper arsenic dust which is made up for the apple 

 of eighty-five pounds of hydrated lime, ten pounds of finely ground 



