ECONOMIC IMPORTANCE OF FUNGI 



295 



3. Alfalfa leaf-spot, the sooty mold of the orange, the 

 powdery mildew of grapes and apples, the wilt disease of 

 cotton and watermelon, the ergot of rye and other cereals 

 (Fig. 215), the black knot of plums and cherries, and the 

 disastrous chestnut disease of the eastern United States. 



284. Chestnut Disease. — The chestnut disease (Fig. 216) 

 first appeared in .the vicinity of New York City about 



Fig. 217. — Map of the northeastern United States, showing the approxi- 

 mate distribution of the chestnut bark disease in rpii. The disease has 

 spread further since the map was made. Horizontal lines, area where 

 majority of trees are dead; vertical lines, approximate area where infection 

 is complete; dots, location of advance infections. (After Metcalf . U. S. 

 Dept. Agr., Farmers Bull. 467.) 



1904, and from there as a center it has rapidly spread 

 until it has destroyed most of the chestnut trees within 

 a radius of 150 to 200 miles of the city (Fig. 217). As 

 many as 17,000 trees have been destroyed in the city of 

 Brooklyn alone, entailing a total loss of several million 



