Cereals 



287 



fungi, and is not cornparable to ordinary 

 molding of dead organic matter by fungi 

 of varying kind. 



Dry-rot (Diplodia zece (Schw.) Lev. 

 and Diplodia macrospora Earle) . — This 

 is one of the very widespread, dry ear 

 rots of corn variously known to growers 

 as mold, mildew, rot, dry-rot, etc. 



Though the disease is really present 

 soon after silking, and even much earlier 

 from root infection, it is not usually 

 recognized until husking, when a whitish 

 covering of the kernels within the husk 

 is noted. This white mycelium also 

 forms dense masses between the indi- 

 vidual grains, among the husks, and over 

 the cob. The grains on the affected ear 

 are shrunken, loosely attached, light in 

 weight, darker in color, and more brittle 

 than those of a healthy ear. Upon 

 breaking open an ear, very small black 

 pycnidia may be seen embedded in the 

 white masses of mycelium, especially at 

 the bases of the kernels. Diseased ears 

 left in the field may develop these pyaii- 

 dia in such abundance as to make the 

 grains black. 



Much of the food value of the corn is 

 lost, owing to the consumption of starch 

 within the grain, as well as to the pre- 

 vention of starch storage. The germi- 

 nating power of the grain is also lost. 



Upon the stalks the fungus first 

 appears as very small dark specks under 

 the rind, near the nodes, and at broken 

 places, usually in over-wintered stalks. 

 Three-year-old stalks have been found 



Fig. 150. — Young 

 ear of com inocu- 

 lated in the silk 

 with Diplodia. Af- 

 ter Burrill and 

 Barrett. 



bearing pycnidia. 



