2^0 Diseases of Truck Crops 



DISEASES OF THE COWPEA {Vigna sinensis) 



In the South, the cowpea is extensively grown as a 

 truck crop. It is cultivated for its edible green pods, 

 and dried peas, and often takes the place of the bean. 



Streak 



Caused by Bacillus lafhyri Manns and Taub. 



Streak is a serious disease which until now has 

 usually been mistaken for other troubles. The disease 

 is the same as streak on the sweet pea and clovers. 



Symptoms. Like the bacteriosis of the bean, streak 

 makes its appearance in a season of heavy dew. On 

 the cowpea it usually appears just as the plant begins 

 to bloom. It is manifested along the stems by light 

 reddish brown to dark brown spots and streaks, the 

 older of which are almost purple, having their origin 

 usually near the grotmd. This indicates distribution 

 by spattering rain and infection through the stomata 

 or through insect injury. The disease becomes 

 distributed quickly over the mature stems until the 

 cambium and deeper tissues are destroyed in con- 

 tinuous areas, and the plant dies prematurely. From 

 the stem the disease spreads to the petioles, peduncles, 

 and pods, the S3niiptoms in these cases being similar 

 to those on the stems. On the leaves, however, the 

 disease appears as small circular spots, which grad- 

 ually coalesce and eventually involve the entire leaf. 

 When killed, the leaf presents a dark brownish ap- 

 pearance. 



