146 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 5 



Station farm. To another portion of the field, Paris green was applied 

 at the rate of one pound to 50 gallons of water. Arsenite of zinc at 

 one pound to 50 gallons was as effective as Paris green and both were 

 entirely satisfactory. At one pound to 75 gallons of water, arsenite 

 of zinc was not entirely effective. 



On cabbages the same insecticides were used and arsenate of lead 

 also. In these experiments, which were made for the purpose of 

 testing the practical advantage of the addition of soap to cause the 

 insecticide to adhere, arsenite of zinc wap used only in the strength of 

 three pounds to 100 gallons of water, while arsenate of lead was used 

 at the rate of six pounds to 100 gallons and Paris green at one pound 

 to 100 gallons. Both of the cabbage pests mentioned were completely 

 controlled and arsenite of zinc did no injury by burning, while Paris 

 green distinctly injured the plants sprayed from the bottom of the 

 knapsack sprayer used. Arsenite of zinc, then was as satisfactory 

 as arsenate of lead and more so than Paris green. 



Cost 



The manufacturers intend this insecticide to be sold at 20 cents per 

 pound retail. Pound for pound it is thus cheaper than Paris green, 

 and considering its relatively high arsenic content, is much cheaper 

 than arsenate of lead. 



Summary 



From the foregoing summary statement it seems to be apparent 

 that neutral arsenite of zinc should have an important place among 

 our arsenical insecticides. 



1. It is finely divided and spreads well. 



2. It is nearly as strong in arsenic as is Paris green. 



3. It has a very low water solubility. 



4. Its suspension qualities are markedly benefited by the addition 

 of a small amount of soap to the water. 



5. Under our tests it has been shown to be less injurious to the bark 

 of the apple tree than any other arsenical compound used. 



6. In killing power it compares well with the standard arsenical 

 insecticides. 



7. Its cost makes it an economical poison to use. 



President F. L. Washburn: We would be very glad to hear a 

 discussion of this paper. 



President F. L. Washburn: The next paper is by Mr. Ball, of 

 Utah, on "The Efficiency of the Driving Spray for the Codling Moth.'^ 



