MARKET DISEASES OP VEGETABLES. 25 



water-soaked spots on the pods. These gradually enlarge 

 and become irregular in shape, the green color fading as 

 the affected tissue dries out. The lesions may have an ele- 

 vated margin. Very soon th,e spots become reddish brown, 

 first at the margins and then in the centers. Finally they 

 turn a darker brown. In this stage the spot dries out and 

 becomes sunken. Under moist conditions, a slime oozes out 

 from the surface of the water-soaked spots. When dry, 

 this exudate forms a translucent or yellow crust. The bor- 

 der between healthy and diseased tissue is not as sharply 

 marked as in bean anthracnose, and is more irregular. The 

 presence of the exudate and the irregular shape of the lesion 

 usually serve to identify blight. 



The bacteria from the pod lesions may penetrate and 

 infect the seeds. Such seeds are marked by yellow spots or 

 blotches of irregular shape or by surface crusts of a yel- 

 lowish color. These spots may show dark red borders and 

 at times a brown or black color. Seeds often are completely 

 yellowed and shriveled. 



Bacterial blight occurs in all bean districts east of the 

 Rocky Mountains. Its spread is favored by moist warm 

 weather, though it can develop in dry weather. It causes 

 severe blighting of the foliage, and may kill plants outright. 

 Pod infection takes place in the field, but the spots may 

 develop or enlarge in transit, and may predispose the stock 

 to slimy soft rot or watery soft rot. 



Blight is a seed-borne infection, and may be controlled 

 only by the use of disease-free seed and. the practice of crop 

 rotation. 



Ref. (15); (75). 



BEAN: SOIL ROT. 



Cause: A fungus (Rhizoctonia). 



Soil rot is characterized by large lesions generally near 

 the end of the pod or at points where the pod has been in 

 contact with the ground. The lesions are large and irregu- 

 lar in shape and light brown in color with soft, badly-rotted 

 underlying tissues. At times the spots are concentrically 

 marked. Anthracnose lesions are smaller and more regular 

 in shape. 



Soil rot occurs only in very moist seasons. The original 

 infection takes place in the field. The fungus spreads from 

 diseased to healthy pods in transit under moist conditions 

 and often causes severe "nesting." The coarse, brown 

 hyphae of the fungus and the sclerotia, if present, distin- 

 guish soil rot from the watery soft rot induced by Sclero- 

 tinia and from the rot caused by Rhizopus, both of which 

 also cause "nesting." 



Soil rot is controllable by careful sorting of the stock and 

 by maintaining a low temperature and humidity during 

 transit. 



