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



Experiment XVI. 



FIELD TESTS OP ARSENATE OP CALCIUM VERSUS ARSENATE OF LEAD AGAINST THE COD- 

 LINO MOTH, 1914. 



One of the most promising of the insecticides tested during the 

 season of 1914 was an arsenate of calcium paste. A commercial 

 article was employed at the rate of 2 pounds to each 50 gallons of 

 lime-sulphur solution. The plat sprayed with this material consisted 

 of 12 trees, the fruit from five of which was examined throughout the 

 season. The plat sprayed with arsenate of lead paste, 2 pounds com- 

 bined with 50 gallons lime-sulphur solution, included 12 trees, the 

 fruit from six of which was examined. Plats III, IV, and V, located 

 in different parts of the orchard, were left unsprayed as a check. 

 These plats had a total of eight trees, all of which were examined. 

 Three applications were given Plats I and II, for the control of the 

 codling moth: (1) When petals dropped; (2) three to four weeks 

 later; (3) nine weeks after petals dropped, for the control of the sec- 

 ond brood. 



The arsenate of calcium paste was analyzed by the Bureau of 

 Chemistry, United States Department of Agriculture, as follows: 



Analysis of arsenate of calcium (p%ste) . 



Per cent. 



Moisture 55. 80 



Total arsenic oxid, As 2 5 18. 82 



Total calcium oxid, CaO 17. 93 



Total lead oxid, PbO 3. 72 



Soluble impurities, exclusive of PbO and As 2 5 1. 84 



Water of constitution and undetermined (small amount of C0 2 ) 1. 89 



Total 100. 00 



Soluble arsenic Trace. 



This sample contains lead equivalent to approximately 5.5 per cent 

 lead arsenate. The results of this experiment are shown in Table 

 XVI. 



Table XVI. — Sound and wormy apples from sprayed and unsprayed plats. 

 [Poison test. A comparison of arsenate of calcium with arsenate of lead. Benton Harbor, Mich., 1914.] 



Plat 



Treatment. 



Tree 

 No. 



Condition of fruit. 



num- 

 ber. 



Wormy. 



Sound. 



Total. 



Per cent 

 sound. 



I 



Arsenate of calcium (commercial paste) , 2 pounds 

 to 50 gallons lime-sulphur solution. 



Plat total 



1 

 2 

 3 

 4 

 5 



123 



78 

 •17 

 44 

 63 



S.0K7 



6, 124 



■1 , 988 

 6,132 

 4,283 



8,210 

 5,502 

 5,035 

 6,176 

 4,346 



98.50 

 98.58 

 99.06 

 99.43 

 9S.56 







866 



28,914 



29,269 



98.79 











