86 



ments for the purpose of determinino- the effect of insecticides on the 

 insect. The notes I have tabnhited below. The resnhs obtained 

 from these experiments indicated the lines of attack which were fol- 

 lowed out a year later in Curtis Park, Denver. 



Preliminary laboratory experiment in 1903 for determining the effect of different 

 insecticides on the cottony niajile scale. 



[Treated January 17, 1903; examined January 23, 1903.] 



Results of a second experiment in 1D03. 

 [Treated January 31, 1903; examined February 10, 1903.] 



Insecticide. 



Strength. 



Eemarks. 



Kerosene emulsion 



Do... 



Whale-oil soap 



Lime-sulphur-siilt (Illinois 

 formula). 



50 per cent kerosene. 

 25 per cent kerosene. 

 1 pound to 1 gallon . . 



Seems to have killed all. 

 Seems to have killed about all. 

 Seems not to have killed any, but there 

 may be ditferent results later. 

 Full I Seems not to have killed any. 



It will be seen by consulting the tables that the mortality of the 

 untreated scale during the winter reaches probably 50 per cent. 

 This is indicated by the counts on the checlv branches and those on 

 which the treatments were so weak as to have had little or no effect. 

 The numbers counted in the laboratory experiments Avere too small 

 to have positive values except where the i)ercentage of dead was very 

 high, because the difference in mortality on different twigs is a 

 conspicuous feature on looking over the hibernating insects. 



The only effective remedies appeared to be kerosene emulsion, 25 

 l^er cent or more in strength, and whale-oil soap at the rate of 1 

 pound to the gallon. The laboratory experiments indicated that 

 further tests with kerosene emulsion, varying in strength from 10 

 to 50 per cent, and the stronger solutions of whale-soap should 

 be made to ascertain more accurately the location of the "dead line." 



