Diseases of Shade and Forest 

 Trees. 



By MEL. T. COOK, State Plant Pathologist. 



The increasing appreciation of the great commercial value 

 of our native forests, and of the importance of trees for 

 shade and ornamental purposes, has stimulated the study of 

 methods for the proper care of trees. This conservation 

 movement has been emphasized by the ravages of the chest- 

 nut blight, or bark disease, and our growing knowledge of 

 other threatening diseases. The fact that it is possible to 

 prevent the loss of many fine trees, which it has required 

 years to grow, makes it very desirable that we should give 

 careful attention to this subject. 



Trees, in fact all other plants, are subject to diseases which 

 are due to more or less well known causes and are as well 

 defined as the diseases which attack animals, causes of 

 Like the diseases of animals, the diseases of <"* 

 plants may cause loss of color, loss of parts, deformities and, 

 in some cases, death. The diseases of both animals and 

 plants are caused by fungi, bacteria, insects, worms, unfavor- 

 able surroundings, etc. Among animals the most common 

 causes of disease are bacteria, while among plants the fungi 

 are responsible for by far the greater number. 



A fungus is a plant which does not possess the green color- 

 ing matter, chlorophyll, and therefore cannot draw its nour- 

 ishment from the air, soil and water, but must live upon 

 other plants and animals, living or dead. Those which live 

 upon and draw their nourishment from living organisms 

 are known as parasites and are the causes of 



,. IT 11 Parasites 



manv diseases; those that live upon dead mat- and 



. mi / saprophytes. 



ter are known as saprophytes. Ihe fungus 



may be so small as to require the use of the miscroscope in 



order to see it, or it may be a minute thread-like structure 



(93) 



