360 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 12 



centimeters of liquid hydrocyanic acid as the ounce equivalent gave 

 a mortality above 99 per cent, it is apparent that the amount of this 

 liquid required to produce results comparable to the 96 per cent mor- 

 tality secured with pot-generation comes within the limits of 16.56 

 and 21 cubic centimeters and approaches the lower figure more closely 

 than the larger. Study of our complete data on purple scale fumiga- 

 tion, supplemented by that on black and red scales, led to the con- 

 clusion that 18 cubic centimeters of high purity liquid hydrocyanic 

 acid approximates the equivalent of one ounce of sodium cyanid on 

 average sized trees fumigated at the ordinary temperatures of treat- 

 ment as closely as any fixed quantity can for orchard work. These 

 results indicate a decided economy of material over the requirements 

 of pot-fumigated trees. 



In the case of red scale on small trees the comparison is not quite 

 as favorable toward liquid hydrocyanic acid as shown by the following 

 experiments which are typical of many performed against this scale: 



Table II. Comparative Scale-Kill on YouNa Trees Between Pot-Generated Ga8 and 97 Per 

 Cent Liquid Hydrocyanic Acid, the Latter Used at the Rate of 16.56 Cubic Centimeters 

 and 19.2 Cubic Centimeters to the Ounce of Solid Sodium Cyanid. The Same Dosage 

 Schedule was Followed for All Trees. 



An examination of the above table shows that the results with liquid 

 hydrocyanic acid at the rate of 16.56 cubic centimeters as equivalent 

 to 1 ounce of solid sodium cyanid were much poorer than for the pot- 

 treated trees. However, where 19.2 cubic centimeters of liquid hydro- 

 cyanic acid for each ounce of cyanid were used the results are about 

 equal to pot-generated gas as taken for the whole tree. These experi- 

 ments show that a slightly less amount of liquid hydrocyanic acid 

 than pot-generated gas is required for small trees. The economy is 

 less than for medium to large sized trees. 



