INSECT PESTS OF OHIO SHADE AND FOREST TREES 173 



Very rarely are the first principles of correct pruning practiced and 

 the tree is not only robbed of its natural and beautiful form but 

 because of the mutilation is rendered particularly susceptible to 

 parasitic attack. Many cities are eliminating this detracting factor 

 from the welfare of their trees by passing legislation to put the 

 wires underground or through the alleys. 



Leaking gas mains a source of tree injury. Another point 

 which may be presented as associated with the problem of insect 

 control in cities is the injury resulting from leaking gas lines. This 

 is an important source of trouble, in many cases being responsible 

 for the death of entire rows of trees. Attention is called to Plate 

 V, Fig. 2, which shows such a row taken in the city of Akron during 

 the summer of 1916. The previous year a gas line running near 

 the trees rusted out, the trees suddenly wilted in midsummer, and 

 were killed before the gas line could be repaired. Gas lines in the 

 vicinity of the tree belt are a constant source of danger, and so far 

 as possible should be eliminated from the streets of the residence 

 sections. In many respects it would be far better practice to extend 

 the lines down the alleys, and if this were the general custom, the 

 danger of injuring trees would be greatly minimized. 



CONTRIBUTING TO THE GENERAL VIGOR OF THE TREE 

 AIDS IN INSECT CONTROL 



Anything that can be done to contribute to the general vigor 

 of the tree is an indirect help in controlling the pests which beset it. 

 Many times trees would be able to withstand the ravages of insect 

 attack were a little assistance given them in the maintenance of 

 vitality by the furnishing of adequate moisture and plant food. 

 With the area normally available to the tree but now greatly re- 

 stricted by overlying pavement and sidewalk, the artificial supply- 

 ing of these materials becomes quite essential. The most common 

 method employed for watering is the insertion of the 3 or 4-inch 

 tiles down into the root system and occasionally filling these with 

 water. Sometimes commercial fertilizers are dissolved and intro- 

 duced through the same channels, but in this process great care 

 should be exercised lest the tree be injured by overapplication. A 

 safer method is the working of manure or commercial fertilizer into 

 the soil over the tree roots. 



THE SCARCITY OF INSECT-EATING BIRDS IN CITIES PARTLY 

 ACCOUNTABLE FOR THE PREVALENCE OF INSECTS 



The final point to be considered of those most closely allied with 

 insect-control problems under city conditions is the comparative 



