FORAGE CROPS 



391 



a faint reddish brown tinge. After the leaves have fallen 

 the stem dies and becomes covered with a light pink coat- 

 ing of the spores of the wilt fungus. The spread of the 

 disease is more gradual 

 and less conspicuous in 

 the early part of the 

 season, but after the peas 

 begin to set fruit they 

 succumb rapidly, and a 

 field that in July may 

 promise a fine crop may 

 be entirely dead before 

 September without hav- 

 ing matured a pod. The 

 disease usually appears in 

 spots, like the cotton wilt, 

 and these diseased areas 

 spread until they may 

 cover a whole field. 



In moderate cases, or 

 where the varieties planted 

 are less subject to the 

 disease, only the weaker 

 plants are killed, while 

 the rest are dwarfed and 



their yield reduced. Careful examination of the roots 

 shows that many of the small lateral roots are dead, small 

 tufts of roots marking the points of infection. Fig. 168. 

 This tufting of the rootlets is similar to that produced on 

 cotton by the cotton wilt fungus. 



In all cases the veins of the stem are brown, and the dis- 



FiG. 168. — Roots of diseased cowpea at 

 left : healthy roots on the right. After 

 Orton. 



