BORING INSECTS 65 



vigor — • or else that they go the way of the dying 

 trees. Allotment companies are great sinners in 

 this connection. They carry out grading and 

 drainage operations which cause the death of 

 hundreds of trees, whose bark and trunk are soon 

 fairly alive with busy hosts of insects. People 

 who buy lots in such vicinities must keep watch on 

 their own trees, and should use their influence to 

 have the sources of infection removed. 



In addition to these measures, which are simply 

 the application of good silvicultural principles to 

 the trees of the city, considered together as a 

 forest, it is extremely important that all trees, and 

 especially trees of a threatened species, or trees in 

 an infested region, should be kept in good health. 

 In some cases fertilization alone will be found a 

 sufficient check upon an epidemic of bark beetles. 

 The most destructive species affect only weakened 

 trees. The way to make them pass by your trees 

 is to see that your trees have a good healthy flow 

 of sap. That means " Water and manure ! " 



We have, then, these rules for the prevention 

 of insect epidemics and attacks: 



1. In planting, select trees suited to the soil 

 and locality, so that they can easily be kept in a 

 thrifty, resistant condition. 



2. In the case of established, as well as newly 

 planted trees, see that the soil is right as regards 

 fertility and physical co;idition, and that the trees 



