40 BULLETIN 27S, 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 larva? 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 lead, 
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 GRAPE. 
With Bordeaux mixture. — Commercial arsenate of calcium and 
homemade compounds were used combined with Bordeaux mixture 
in vineyard experiments. These combinations caused no foliage 
injurv. 
ARSENATE OF IRON. 
LABORATORY AXD 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 
