vi PREFACE 



a living organism which requires water, food, air and sunlight 

 is often overlooked. Many of the diseases outside the forest 

 are due to the failure to recognize the importance of main- 

 taining suitable conditions for tree growth. The soil must 

 contain the proper supply of food materials, and be of a texture 

 which will conserve the water and air that are necessary for 

 healthy root development. Pavements and sod are frequently 

 never considered as the cause of the decline and death of trees. 

 Likewise, it is seldom appreciated that the smoke and poisonous 

 gases in the atmosphere in cities kill many trees. Also the 

 appearance of leaf-spots, cankers, wood-rots and root-rots in 

 no way explain themselves unless it is understood that in- 

 visible parasitic plants are growing in the living tissues of the 

 tree and causing their death. The technical facts regarding 

 the relation between a tree and its environment are more easily 

 comprehended than the life history of the parasites which cause 

 diseases. Nevertheless, the tree owner must understand the 

 nature of these organisms, the appearance of the symptoms 

 they produce, and many other facts regarding diseases before 

 he can intelligently attempt their control. It is hoped that 

 the details concerning the diseases discussed in this book will 

 assist to that end. The treatment has been made as simple 

 as possible, and only the essentials regarding the disease, which 

 are necessary to recognize and understand it, have been in- 

 cluded. A glossary is appended," which will assist in explain- 

 ing the more technical terms. 



It has been necessary to treat the general and specific diseases 

 separately. Those diseases which are more or less common 

 to all kinds of trees are discussed in the first four chapters. 

 The more specific diseases will be found in the chapters follow- 

 ing, which are arranged alphabetically according to the com- 

 mon name of the various groups of trees. Cross-reference 

 has been freely made in the different chapters to more complete 

 discussions found elsewhere. This would be unnecessary if 



