57 



of equipment fumig-ation is by far the most expensive, especially 

 if the trees to be treated are larg-e, but the three insecticide sprays 

 are prepared and applied by the aid of practically the same appa- 

 ratus. 



The cost of preparation and application is not materially dif- 

 ferent for the four insecticides under discussion, and will at any 

 rate vary greatly in practice according- to individual circumstances. 



With respect to cost of materials, the fumig-ation process is 

 much the most expensive. At Richview, where the trees treated 

 were usually of medium size or less, the cost was nine cents a tree 

 for fumigation materials, while at Sparta, where the trees averaged 

 much larger, this cost was eighteen cents a tree. At the latter place 

 whale-oil soap, although applied only to the largest trees as a rule, 

 was used at a cost of seven cents a tree for the soap itself. At 

 Carterville and Browns the average cost of lime, salt, and sulphur 

 for the California wash was two to three cents, according to the 

 size of the trees, while the general average per tree for kerosene 

 emulsion as applied to over 5,000 trees was two cents each. 



In convenience of application the preference belongs clearly to 

 the kerosene emulsion and the California wash, the use of whale- 

 oil soap being frequently embarrassed in very cold weather by the 

 solidifying of the solution in the hose if the flow is stopped, and 

 the operation of fumigation being a laborious and complicated one 

 for trees above medium size. 



It follows from the foregoing that of these various insecticide 

 methods and materials the best for common use against the San 

 Jose scale is spraying in winter with the California wash. 



