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JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 8 



forms, beginning in 1912, for the control of the codling moth and other 

 deciduous fruit insects. During the season of 1914, a commercial 

 arsenate of calcium (paste) containing 18 per cent arsenic oxide 

 (AS2O5) was tested against the codling moth in our experimental 

 apple orchard, Benton Harbor, Mich. This was used at the rate 

 of 2 pounds to 50 gallons of lime-sulphur solution in comparison with 

 arsenate of lead paste, used at the same rate, combined with lime- 

 sulphur solution. Three spray applications were made: (1) When 

 the petals dropped. (2) Three to four weeks later. (3) Nine weeks 

 after falling of the petals for the control of the second brood. 



The arsenate of lime plat included 10 trees, the fruit from 5 of which 

 was examined as it dropped during the season and again at harvest 

 time. The arsenate of lead plat contained 12 trees — 6 examined. 

 The unsprayed plat consisted of 8 trees, the fruit from each tree being 

 examined. Each plat produced approximately forty barrels of fruit 

 at harvest, which was inspected for codling moth injury. The arse- 

 nate of calcium and arsenate of lead plats gave over 98 per cent of 

 fruit free from the codling moth, while the unsprayed plat yielded 

 about 59 per cent of fruit free from this injury. The foliage of the 

 arsenate of lime plat compared favorably with that of arsenate of lead 

 throughout the season. 



We have prepared arsenate of lime by adding sodium arsenate to 

 slaking lime. This arsenical may be prepared from other chemicals, 

 such as a combination of arsenic acid and lime. According to our 

 figures, a good arsenate of lime paste may be made at a cost of two 

 to three cents per pound, exclusive of labor. We have recently pur- 

 chased fused sodium arsenate (65% AS2O5) at 8 J cents per pound 

 and stone lime at 75 cents per barrel. From these materials we have 

 made arsenate of lime paste, containing over 20 per cent arsenic oxide, 

 at a cost not to exceed 3 cents per pound. The biproduct, sodium 

 hydroxide, if not removed, may injure delicate foliage. Most of the 

 sodium hydroxide, however, may be readily decanted. 



Arsenate of lime was made in the same operation of slaking the 

 lime for Bordeaux mixture for use in an experimental vineyard. No 

 foliage injury resulted. 



Arsenate of lime has not been tested sufficiently to warrant an 

 unqualified recommendation. This arsenical may have certain hmi- 

 tations, but it is apparently a promising and cheap insecticide. 



Me. W. C. O'Kane: I would like to ask Mr. Scott whether he has 

 any determination showing the soluble arsenic in the material. You 

 state that there is sometimes burning of foliage and sometimes not. 

 If the free arsenic is a variable quantity, it seems to me that the 

 material offers some risks in its effect on the plants sprayed. 



