20 SHADE TREE GUIDE. 



cities where the service is concentrated; they must therefore be 

 carried on poles along the streets and must be accommodated to ex- 

 isting structures and trees. In making these accommodations five 

 rules will govern : 



1. Set the poles as far out of the tree line as possible, to avoid 

 interference. 



2. Use low rather* than high poles. Where the trees are small, 

 and in line with the poles, it is necessary to carry the wires above 

 them, but as they grow, lower the poles so that the wires may be 

 carried, on offsets, brackets and insulators, away from or thru the 

 firm bodies of the trees. A wire fastened so that it does not rub 

 can do no harm ; a bolt carefully driven into the heart of a branch 

 to support an insulator or a cross arm is always justified; but any 

 vigorous tree will soon outgrow the practical height of electric poles. 



3. Let cross arms and insulators be fastened to strong trees, 

 rather than set poles, where the wires can be properly carried. 



4. Provide guard strips on the. trees and abrasion moulding on the 

 wires wherever there is movement and a chance that the tree and 

 the wire will rub. The removal of small interior branches to make 

 a clear way for a wire is more apt to be a benefit than an injury to 

 a tree. 



5. Have all cuts larger than I inch diameter made smooth and 

 carefully treated (see p. 14), to prevent the entrance of disease 

 germs. Prohibit absolutely the use of climbing spurs in any tree. 



Diseases 



The diseases of trees are chiefly due to abnormal soil or climatic 

 conditions, to injuries, or to .parasitic fungi. The latter sometimes 

 are very destructive, as in the case of the chestnut blight ; more 

 commonly, as the sycamore anthracnose, they affect the foliage 

 more or less seriously, but do little permanent harm. Fortunately, 

 most diseases attack only one tree species, or one genus, a law 

 that makes diagnosis and control less difficult than they would be 

 otherwise. If a tree begins to fail without apparent cause, it should 

 be questioned (i) whether it lacks water; (2) whether it stands 

 in sterile soil and lacks fertilizer. If either deficiency is discovered 

 the remedy is obvious (see p. 13). If it is not, a specialist may 

 be helpful; often he can do nothing. If the fleshy fruiting bodies 

 of a fungus appear, the tree, or its affected member, is seriously 

 diseased, and surgery, or the tree's removal, is indicated. It fre- 

 quently is better to ignore the signs of internal decay than to start 

 a cutting which may have no practical limits. Many trees live for 

 years with their heartwood completely gone. (See Cavities, p. 16). 

 It is important to distinguish the fungus fruits which appear only 

 on dead wood, from those which are parasitic. A special publica- 

 tion, "Common Diseases of Shade Trees/' can be obtained upon re- 

 quest of the State Agricultural Experiment Station, New Bruns- 

 wick. 



