CHESTNUT DISEASES 139 



the one caused by Septoria ochroleuca is important. The large 

 leaf-spot is common in the South. Powdery mildews are 

 also common on chestnut leaves. The wood of the trunk is 

 decayed by several fungi and the shoe-string root-rot is very 

 destructive to chestnut (see page 78). 



Large Leaf-Spot 



Caused by Monochcetia Desmazierii Sacc. 



Chestnut leaves are commonly affected by leaf-spot diseases. 

 The one here designated as the large leaf-spot is known to occur 

 in the southern Appalachian region in Virginia, North Carolina 

 and Georgia. It is often abundant, and causes some damage 

 by decreasing the functioning leaf-surface. Red oak leaves are 

 affected by the same disease. 



Symptoms. 



The symptoms are similar on the chestnut and red oak. 

 Small circular spots appear which are a quarter to one-half 

 inch in diameter, with a pale center and darker surrounding 

 zones, varying in color from yellow and gray to red-brown. 

 These spots enlarge rapidly and sometimes extend entirely 

 across the width of the leaf. Two or three such spots cause 

 the death of most of the leaf-tissue. The bands of colors as 

 described above are present in the older and larger spots. On 

 the under side of the leaf there is less evidence of the colored 

 zones and superficial mycelium of the fungus at the margin of 

 the spot causes a mildewed appearance. Early in the develop- 

 ment of the spots, numerous densely crowded black dots appear 

 on the dead leaf-tissue. 



Caiise. 



Large leaf-spot of chestnut and red oak is caused by the 

 conidial stage of a fungus known as Monochcetia Desmazierii. 



