B. P. I. 450. 



DISEASES OF DECIDUOUS FOREST TREES. 



INTRODUCTION. 



Deciduous forest trees are affected with a large number of different 

 forms of disease, some of which are daily assuming more and more 

 importance. While it has been well known for many years that 

 there are such diseases which are prevalent among broadleaf forest 

 trees, very little has been accomplished up to the present time in 

 the study of their occurrence, the amount of destruction which they 

 cause, and the practical methods of prevention. In dealing with 

 timber tracts, whether they be wood lots or larger areas, it is becom- 

 ing of increasing importance to take cognizance of those factors 

 which cause depreciation in value of the timber produced, either by 

 decreasing the value of the wood cut or by retarding or preventing 

 the growth of the trees themselves. The various types of disease 

 affect both young and old trees, and from the time the seedling 

 starts to develop until it has reached maturity it is liable to attack 

 by one or more destructive diseases. 



In the present bulletin the results of a number of years' investi- 

 gation of some of the more important diseases of deciduous trees are 

 discussed. No attempt is made to include in this paper all of these 

 diseases. Manv are local in their distribution and are as vet of minor 



, / 



importance from a practical standpoint. Many of them affect shade 

 and ornamental trees rather than forest trees. All such are left for 

 subsequent discussion. 



For the sake of convenience the diseases of trees may be divided 

 into several groups. Basing the classification on the causes of dis- 

 ease, they may be divided into those caused by unfavorable envi- 

 ronmental conditions, including smoke or injurious gases, extreme 

 cold, lightning, excessive water supply, etc., and those caused by liv- 

 ing organisms animals, insects, flowering plants, fungi, and bacteria. 

 Those fungi which cause disease may again be classified into such as 

 grow in the living parts of the tree, including the leaves, the younger 

 branches, the newly formed wood and bark, and the living portion 

 of the root system, and those which grow on the dead or dying parts 

 of the tree, including the heartwood of the trunk, branches, and 

 roots. 



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