80 



Diseases of Economic Plants 



turning them brown, soft, and rendering them worthless. 

 Aside from injuring the mature fruit, the rot attacks the 

 flowers and twigs. The disease ranges over the entire peach- 

 growing territory, but is usually most severe in the South. 

 In some years the loss has amounted to more than 50 per cent 

 of the crop, or an aggregate annual loss of $5,000,000. The 

 estimated damage in Ohio alone in one year was a quarter 

 of a million dollars; in one year in Pennsylvania twenty 

 carloads were lost. Apples, pears, and quinces are attacked, 

 but to lesser extent. 



Its characteristic appearance on the fruit enables one to 



recognize it easily. It fir^t appears as small, circular, brown, 



decayed spots. These rapidly en- 



1 large until they embrace the 



^P whole fruit, which at the same 



4^^ ^^ time shrinks slightly. As the 



j\^^^Bf decay advances, small tufts of 



^^IJ^^I^B ^_^ brown threads appear near the 



^^Q^^^^K^fl^k centers of the original spots, and 



J^^^^^^^^^^B^ spread rapidly until the whole 



^^^^^^^^^^^B If the fruit hangs in clusters, 



^i^^^^HpP adjacent fruits begin to decay at 



^^^^^ the points of contact, and the dis- 



FiG. 41. — Mummy peach 

 showing Sclerotinia asco 

 phores. After Scott. 



ease spreads from fruit to fruit un- 

 til whole clusters are lost. Fruit, 

 after it is picked, may also suc- 

 cumb to attack, and peaches that 

 were apparently sound at picking may be seriously damaged 

 when they reach market. Thus the loss falls upon grower, car- 

 rier, dealer, and consumer. The decay is so rapid that infection 

 to-day may mean a totally unsalable peach two days hence. 

 Peaches diseased on the tree may fail to the ground, or remain 

 on the tree, where they shrivel and hang over winter, to con- 

 stitute the "mummy" peaches so familiar in infected orchards. 

 Upon the blossom the disease is first evident as a slight, 

 brownish discoloration, which spreads rapidly, causing the 



