230 DISEASES OF ECONOMIC PLANTS 



Black mold (Alternaria Brassicoe (Berk.) Sacc). — The 

 affected spots are nearly black, marked concentrically, 

 are circular, and are not definitely bordered, i.e., they 

 shade off gradually into the surrounding healthy tissue. 



Fig. 108. — Collard black mold 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. 



The general appearance of the spot as seen from above 

 is pale green ; as seen from the lower surface, shown in 

 Fig. 108, it is densely black, strongly contrasting with 



