Lack of aseptic and antiseptic treatment in cases of wounds 

 arising from accidental or intentional pruning, or from injuries from 

 horses' teeth, abrasions from teams, etc. 



Interference to tree growth by telephone w-ires. 

 Electrical injuries due to contact with alternating and direct cur- 

 rent wires. 



Injuries due to leaks in gas mains, steam conduits, etc. 



'These, factors, singly or in com- 

 bination, constitute a menace to 

 trees, and it is only by an under- 

 standing of the effects that we can 

 comprehend their importance as 

 agencies detrimental to tree devel- 

 opment, and obtain a rational con- 

 ception of the aetiology of disease. 

 Some of these factors are so detri- 

 mental to tree development that the 

 largest species will succumb in a 

 relatively short time. In most cases, 

 however, trees subject to adverse 

 conditions linger along in a state of 

 malaise or weak condition, thereby 

 easily falling a prey to parasites. 



Insect and fungous pests are fre- 

 quently troublesome. They are 

 however often secondary, that is 

 they frequently occur as a result of 

 some weakened condition of the tree, 

 arising from either a single cause or 

 combination of causes. Moreover 

 the changes which take place in its 

 environment due to the introduction 

 or expulsion of birds and insects 



frequently disturb the beneficial rela- 

 Fig.\. Showitw tlie destructive.- ,• • .■ i . .. 



effect on the gro^uth of a maple //r^tionship existing between them to 



in contact zuith a mass of -wires. such an extent as to render pests 



more obnoxious. The general 

 hygienic conditions, however, that are characteristic of our cities are 



f • J 



