40 BULLETIN 278, U. S. DEPARTMENT OF AGRICULTURE. 



in the experimental work during 1912, 1913, and 1914, and has 

 given encouraging results. This arsenical can undoubtedly be manu- 

 factured at a somewhat cheaper cost than arsenate of lead. It is 

 of further interest to note that this compound may be readily pre- 

 pared at home by combining fused sodium arsenate with stone lime. 

 (For a discussion of the method of making, see p. 30.) While it 

 would be preferable to use arsenic acid in place of sodium arsenate, 

 this acid can not be readily secured at low cost at the present time. 

 When arsenic acid is used the method of preparation as described 

 should be modified somewhat. 



LABORATORY TESTS. 



Used alone. — Arsenate of calcium, commercial powder and paste 

 and homemade paste, in accordance with several formulas, was used 

 in poison-feeding tests with several species of chewing insects. In 

 some instances the rapidity of killing was equal to that of arsenate 

 of lead, but was generally somewhat less. 



With lime-sulphur. — With lime-sulphur, arsenate of calcium was 

 as a rule more effective as a poisoning agent than when used alone. 

 When these compounds are combined, the amount of foliage consumed 

 by the larvae is less than when arsenate of calcium is used alone. 



FIELD TESTS WITH APPLES. 



With lime-sulphur. — During the years 1912 and 1913 the several 

 forms of arsenate of calcium combined with lime-sulphur gave fairly 

 satisfactory control of the codling moth, considering the strength of 

 the arsenical used. In 1914 a commercial arsenate of calcium 

 (paste), arsenic oxid 18.82 per cent, combined with lime-sulphur 

 solution, gave very excellent control of the codling moth in com- 

 parison with arsenate of lead and unsprayed plats; arsenate of 

 calcium, 29,269 apples, 98.79 per cent sound; arsenate of lend, 

 24,018 apples, 99.44 per cent sound; unsprayed, 47,866 apples, 5S.71 

 per cent sound. It is of further interest to note that arsenate of 

 calcium may be combined with lime-sulphur without lessening the 

 value of the latter as a fungicide. 



FIELD TESTS WITH CRAPE. 



With Bordeaux mixture. — Commercial arsenate of calcium and 

 homemade compounds were used combined with Bordeaux mixture 

 in vineyard experiments. These combinations caused no foliage 

 injury. 



ARSENATE OF IRON. 



LABORATORY AND FIELD TESTS. 



Arsenate of iron is a slower acting poison than many of the other 

 arsenicals tested. Laboratory tests, even at increased strengths, 

 show that this arsenical is not quick to kill. In the field tests at the 



