EXPERIMENT STATION BULLETINS. 



277 



It is well knowu that all trees do better under natural conditions than 

 under artificial ones. We have all noticed the lack of health among the 

 trees in slashings, where many of the trees have been cut and where the 

 grass has taken possession and sodded the ground. The trees are never 

 so healthy in such places. The general vitality of the trees is weakened 

 and then the borers come, especially the bark-beetles. These injects 



Fig. 26 — Tunnels of hickory bark-beetle in bark, nat. size. Original. 



always select sickly trees, if any such are present. Parks are ahvays more 

 or less unnatural. It is not possible to preserve the loose, leafy covering 

 for the soil, the surface becomes packed and in many places sodded, and 

 where many trees are living close together, a disease spreads easily from 

 one to another. 



In cases like the present, where bark-beetles are at work, the only 

 method known is to cut out such trees as are being used for breeding 

 places. This does not include those whose twigs alone are affected, but 

 those containing chambers under the bark. This should be done to cut 

 off the supply of beetles in the hope of checking the trouble. The trees 

 should be stimulated if possible in order to keep them in perfect health 

 and in a condition distasteful to the beetles. 



