Trees and Timber 379 



excavated and disinfected and left without filling. Tree 

 surgery should be done in mild weather, when the sap is not 

 running actively. 



The necessity of surgical work can largely be avoided by 

 early attention to wounds and especially by avoidance of 

 wounds, and l\y the use of proper tree protectors and care in 

 guying and staying branches to prevent galling or constric- 

 tion. 



Leaf-spots, flower-blight. Numerous fungi cause spotting 

 of leaves or disease of flowers of trees. These injuries are 

 in general similar to leaf-spot, for example of celery, tomato, 

 and other crops discussed on preceding pages. Ordinarily the 

 injury in forests is not large, and treatment or even sanitary 

 measures are out of the question. In the case of valuable 

 shade, nut, fruit, or ornamental trees, or of nursery stock, 

 spraying or dusting with fungicide is often advisable. Only 

 the more important of the tree leaf diseases are discussed 

 below. 



Following is a list of many of the fungi of leaf and flower 

 diseases of trees with the hosts they most commonly infect. 

 Page references are to further mention in other parts of this 

 book.* 



Fungus Hosts 



Acanthostigma. Hemlock and conifers generally. 

 Ascochyta. Butternut, oak, walnut. 



Asterina. Magnolia, oak. 



Cercospora. Ash, butternut, catalpa, linden, p. 391, 



maple, pecan, red-bud, sequoia, willow. 

 CoUetotrichum. Magnolia. 

 Cylindrosporium. Alder, ash, birch, elm, hackberry, locust, 



maple, walnut. 

 Didymosphaeria. Catalpa. 

 Entomosporium. Hawthorn. 

 Fusicladium. Pecan, p. 394. 



* Books to aid in the study of these fungi are listed in the bibhography 

 under numbers 390-394. 



