EXPERIMENT STATION BULLETINS. 



467 



or granular form and when exposed at a temperature of 55 to 60 degrees or 

 higher, it vaporizes to a gas which is about six times heavier than air. The 

 crystals, which are placed around the base of a peach tree, vaporize into this 

 heavy gas which penetrates through the soil into the borer tunnels and acts 

 as a poison to the borer. 



The method of application used in all the experiments here reported was 

 as follows. The soil around the base of the tree was made reasonably level 

 and smooth without digging it up. Any grass or weeds around the tree were 

 removed and excessive exudations of gum close to the ground were also re- 

 moved. When there were any indications that there were borers five or six 

 inches above the normal level of the soil, the soil level was raised to that 

 point. 



The para-dichlorobenzene was then spread around the tree in an even band, 

 about lyz inches wide, and at about the same distance from the tree. The 

 material had previously been put through a wire screen of about 10-mesh 

 fineness (ordinary window screening has about 10 meshes to the inch) to 

 break up any lumps. A mound of soil four to six inches deep was then placed 

 over the para-dichlorobenzene and packed lightly with the back of a shovel. 



Fig. 19. — A mound of soil 4 to 5 inches high placed around tree and over the para-dichlorobenzene. 



