42 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



to bordeaux mixture, which sticks it to the foliage, and it may be 

 used to good advantage for fighting grasshoppers and leaf-eating 

 caterpillars when it is desired to poison considerable areas of 

 weeds or waste grass. The so-called Kedzie formula (See Sodium 

 arsenite below) is the most satisfactory, as the soda hastens 

 the complete combination of the arsenic, and the resulting 

 solution is in a clear liquid form which can be readily measured.* 

 6. Ar senate of calcium, sometimes called arsenate of lime, is 

 an insecticide of more recent application and is perhaps the best 

 substitute for arsenate of lead. It has several points in its favor 

 over the lead compound, being cheaper under normal conditions, 

 and possessing greater killing power, pound for pound, since a 

 pound of the calcium arsenate has a greater percentage of arsenic 

 than does a pound of lead arsenate. It is somewhat more liable 

 to scorch foliage than is the lead arsenate and it is recommended 

 that it be always used with some stone lime added. It is not a 

 safe material, according to latest reports, to use on peach foliage. 

 Calcium arsenate is marketed as a paste and also in the dust form. 

 It has been used as a substitute for lead arsenate in dusting work 

 It may be prepared at home but the same objections are to be 

 raised as against the home manufacture of lead arsenate. The 

 formula and directions follow: 



Stone lime, best grade 2 Ibs. 



Sodium arsenate, fused (65% As 2 O 5 ) 4 Ibs. 



Water 1 gallon. 



Dissolve the sodium arsenate in a little hot water. Place the 

 stone lime in a wooden tub or bucket and add just enough water 

 to start slaking. Then add the dissolved sodium arsenate. Stir 

 constantly and add small amounts of water from time to time 

 until the slaking has ceased. Allow the solids to settle and pour 

 off the clear liquid above. The resulting paste is calcium arsenate 

 and may be used at from one to three pounds per barrel of water. 

 Impurities in the materials used may reduce the killing power of 



* Arsenite of lime is often made by boiling 1 pound of lime with 2 pounds 

 of white arsenic in 1 gallon of water for thirty to forty-five minutes. This 

 results in a paste of arsenite of lime, which settles in the solution. One quart 

 of this mixture is used per barrel of water or Bordeaux mixture, but unless 

 the stock solution is always stirred equally well, the amount of poison in a 

 quart will be quite variable, with varying effectiveness; hence the clear solu- 

 tion of arsenite of soda as in the Kedzie formula is preferable. 



