160 SHADE-TREES IN TOWNS AND CITIES 



City and has killed hundreds of trees. In the northern 

 section of the State of New Jersey, a great many of the 

 sugar maples died in 1905 and 1906 as a result of the injuries 

 inflicted on these trees by the sugar-maple borer and the 

 leopard moth a few years before that time. The gipsy moth, 

 perhaps the most destructive of all tree-pests, has become 

 firmly established in Massachusetts. 



Even in the forest the annual loss of trees from insect 

 pests is very great ; but in cities the unfavorable conditions 

 to tree growth are contributory causes that make them still 

 more vulnerable to attack. Like animals, trees can resist 

 disease to a greater degree when they are in a healthy condi- 

 tion. Many insects do not attack trees until they show signs 

 of weakness, and that is especially true of borers. Generally, 

 then, it may be said that one of the best methods of prevent- 

 ing insect injury is to keep trees in as thrifty a condition as 

 possible. It should always be remembered that trees have 

 life different in kind, perhaps, from that of animals, but 

 nevertheless a life that needs nourishment and favorable 

 conditions for the maintenance of vigor. 



While protective measures are extremely important, there 

 will be visitations of diseases and pests that will require 

 remedial treatment. Besides, insects are dependent during 

 their development on plant food, certain species preferring 

 certain trees, so that from a natural standpoint the insect 

 possesses its right to exist just as other forms of life. It is 

 admitted, however, that this point of view is not consoling 

 to one whose trees have been killed by caterpillars, borers, 

 or other pests. It should be recognized as absolutely im- 

 perative for the owner of one tree or a thousand trees to 

 be prepared to combat insects when a visitation occurs. 



Insects feeding on trees are always present ; but some- 



