164 



JOURNAL OF ECONOMIC ENTOMOLOGY 

 TABLE II 



[Vol. 7 



Note. — Arsenate of lead as found on the market was used. AseOi calculated on drj' basis. 



From the above table it is readily seen that when derived from the 

 neutral or acid arsenate of lead, 33 units of AsoOs gave practically 

 the same control as 37 units and that an excess of the units used above 

 33, therefore, does not give a corresponding decrease in the percentage 

 of wormy fruit. This indicates also that the percentage of AS2O5 

 and not the form, determines the killing power. 



A different grouping of the data already given with the addition 

 of the facts obtained from a plot (No. 4) on which 3j pounds of 

 basic arsenate of lead was used will bring our two other points, viz.: 

 basic arsenate of lead did not become available under the existing 

 climatic conditions in sufficient degree to give good control, and 

 second, an excessive increase of the number of units above 33 does 

 not give a corresponding decrease in the percentage wormy. 



TABLE III 



The table above combined with the two previousl}' given indicates 

 the following facts: 



1. The lowest number of units of AS2O5 necessary t'o give an effective 

 control of the plum curculio is 33 (Plots 13, 7, 8). 



2. One pound of an acid arsenate of lead (33% arsenic oxide) has 

 more killing power than a pound of neutral arsenate of lead (25% — 

 27% arsenic oxide), and each more killing power than 1 pound of 

 basic arsenate of lead (20 % arsenic oxide) (Plots 1, 2, 3). 



3. Under similar climatic conditions, the killing power of an acid 

 or a neutral arsenate of lead depends directly upon the percentage 

 of AS2O5 that it contains. 



