374 UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION. 



not penetrate, crack, deteriorate, or bind the tree, since it yields to the 

 slightest pressure. Four years of experimenting have not shown the 

 least injury. 



The material is applied warm with a brush from five inches below 

 to five inches above the ground. It is easier to apply two or more coat- 

 ings than to try to put on more at one time than will adhere firmly. The 

 first coating will harden very quickly and the second can be applied 

 without loss of time. Two coatings are generally sufficient unless the 

 bark is very rough. But in any case a thick, uniform covering is abso- 

 lutely necessary for the best results. 



Borers are seldom uniformly distributed over an orchard. Small 

 blocks of trees here and there may be badly infested and the most of 

 the orchard comparatively free from the pest. In such cases it is not 

 necessary to treat all of the trees with asphaltum, but it is necessary to 

 examine them carefully, for in no other way can the true conditions 

 be known. 



A convenient way to handle the asphaltum is to mount an iron kettle 

 on the running gear of an orchard truck and suspend beneath it a sheet- 

 iron apron as a fire box. Keep hard asphaltum in the kettle all the time 

 so that the melted asphaltum will not get too hot to carry in small con- 

 tainers and apply directly to the trees. 



We have also used asphaltum to a limited extent for covering wounds 

 and for grafting. And although our experiments are not completed, we 

 believe it may become very useful as a dressing for tree surgery. 



SUMMARY. 



In the fall throw the soil away from the trees and dig the borers. In 

 the spring dig the borers again and apply a thick coating of asphaltum 

 and replace the soil. Examine the trees each subsequent year to remove 

 borers and to repair any thin or broken places in the asphaltum coating. 



