232 SHADE-TREES IN TOWNS AND CITIES 



the same street, undesirable mixed with desirable, of all 

 shapes and sizes, set either too closely or too far apart. In 

 some cases the trees are not trimmed at all and the limbs 

 are so low as to touch the heads of pedestrians; in others 

 they are pruned too high. The trees have been left unpro- 

 tected by guards, many of them have been bitten by horses, 

 and there is evidence that they have been injured by 

 destructive pests. The writer has had the opportunity of 

 studying the street-trees of a great many towns and cities 

 in different parts of the country and the conditions de- 

 scribed above are universal. 



Especially in the control of insects which infest certain 

 species of trees from time to time the system, or rather the 

 lack of system, of the individual care of street-trees utterly 

 fails. The citizen is entirely powerless to accomplish any- 

 thing. He may plant an undesirable species of tree if the 

 task is left to him, but in insect fighting he will do even less. 

 His efforts will come to naught if his neighbor allows the 

 pest to remain on his trees. In the extermination of insects 

 in a city it is absolutely necessary that all the infested trees 

 be treated in order to obtain effective results. It is impossi- 

 ble to have concerted action on the part of thousands of 

 people of a community in the treatment of infested trees at 

 the same time. Insect fighting requires persistence and 

 knowledge of what to do at the proper time to obtain results. 

 There is a period in the life history of most of our tree pests 

 when it may be most easily destroyed. This stage is not 

 always at the time when the most injury is apparent, or 

 when the average citizen wakes up to the necessity of doing 

 something. The life history of the pests must be known 

 in order that treatment may be given at the right time. 

 Besides, to spray trees of considerable size requires aa 



