INSECTS, DISEASES, AND INJURIES 147 



Smoke and fume injury. 



In manufacturing cities and in the vicinity of smelters, 

 pulp and fertilizer mills, brick-kilns, coke-ovens, and blast- 

 furnaces, particularly where sulfur gases are produced, the 

 effects on all kinds of foliage are very evident. Evergreens 

 in general are most sensitive, probably owing to the long life 

 of their individual leaves. Junipers, however, show a distinct 

 resistance, while pines and firs are much more susceptible. 

 The degree of injury is governed by the distance from the 

 source of the smoke and fumes, by the direction of the pre- 

 vailing winds, and by the topography of the ground. Injured 

 trees show a dying and browning of the needles from their tips. 

 There may also be a curling of the leaves, while the trees are 

 generally stunted and of a sickly appearance. The injury may 

 result in defoliation and ultimate death of the trees. 



Unfortunately, there is no control measure for this trouble 

 within the power of the individual grower. It is a case of 

 either smoke and fumes or trees having to go. Smoke and fume 

 prevention on the part of the manufactories concerned is the 

 only remedy if the more susceptible evergreens are to be grown. 

 The planting of junipers in districts in which the trouble is 

 most acute should be considered. 



Electrical injuries. 



Electrical injuries may be divided into those due to the 

 natural phenomenon of lightning and those caused by high 

 tension line wires. 



The common effects of lightning are probably familiar to 

 all; but trees may be injured in a number of freakish ways, 

 some of which are more difficult of diagnosis. Sometimes trees 

 are cleft longitudinally or are completely shattered by very 

 powerful discharges. When these are less powerful, strips of 



