170 



Diseases of Economic Plants 



South, this mold is quite destructive both in the field and in 

 storage. The affected spots are nearly black, circular, 

 marked concentrically, and are not definitely bordered, i. e., 

 they shade off gradually into the surrounding healthy tissue. 



Fig. 92. — Black-mold on oollard as seen from 

 upper side of the leaf. Original. 



They enlarge sometimes to 2-3 cm. in diameter. The tissue 

 dries, becomes brittle, and often falls away, leaving ragged 

 holes. 



In many instances the plants die or fail to mature. In 

 storage the spots continue to enlarge, and it is here that the 

 greatest loss occurs. Storage houses should be disinfected 

 with Bordeaux mixture, and temperature and ventilation 

 regulated as suggested under soft-rot, p. 172. 



Drop -^^ {Sclerotinia Uhertiana). — This malady is dis- 

 cussed luider lettuce. Upon the cabbage, rape, cauliflower, 



