CONTENTS 



I. Introduction 165 



II. Factors associated with insect control in cities 167 



1. Effective insect control depends on the selection of suitable 

 species of trees and in their proper planting 167 



A. The correct selection of species for planting, the first step 

 toward insect control 167 



B. Select healthy, vigorous trees for planting 166 



C. Plant to allow an opportunity for development 169 



D. Avoid planting large areas to a single species 169 



E. Planting of small units to a single species commendable . . 170 



F. Plant to make insect warfare possible 171 



2. Contributing causes of decreased vitality of trees 171 



A. Street trees require protection from mechanical injuries. . 171 



a. Biting of horses .^ 171 



b. Mutilation by passersby 172 



c. Injuries by builders 172 



B. Overhead wires a menace to the health of trees 172 



X,. Leaking gas mains a source of tree injury 173 



3. Contributing to the general vigor of the tree aids in insect 

 control 173 



4. The scarcity of insect-eating birds in cities partly accountable 



for the prevalence of insects 173 



III. Insect control possible under city Conditions 174 



IV. Intensive control measures rarely possible under forest or 



wooDLOT conditions 175 



v. Establishing a municipal tree-treating department 175 



1. Insect control in cities a municipal problem 175 



2. Proper legislation the first step necessary 176 



3. Organization of the department 180 



A. The commission plan 180 



B. The city department plan 181 



4. A civil service basis desirable 181 



5. Scope of work 183 



6. Cost of maintenance 184 



VI. Tree doctors, quacks, etc 185 



VII. Spraying machinery and accessories 185 



1. Spraying machines of the mist or fog class 186 



A. Hand driven mist sprayers 187 



B. Power driven mist sprayers 187 



C. Operating a municipal mist sprayer 188 



(161) 



