342 Minnesota Plant Diseases. 



has also been recommended but is an uncertain aid and is 

 doubtfully of use. 



Bean leaf b\ight(Pseudomonas phaseoli Smith). This disease 

 is of bacterial origin. It has not been reported from Minne- 

 sota but is well known in the eastern United States. It causes 

 a brown tipping of the leaves or dead spots in the leaf. The 

 entire leaf may die. Bean insects, irrigation and mulching are 

 said to have a tendency to increase the disease and certain vari- 

 eties are more susceptible than others. 



Black rot of cabbage (Pseudomonas campestris Smith). This 

 is a bacterial disease and causes a rotting of the plant. Cab- 

 bage and a large number of related plants are affected. The 



FIG. 174. P>lack rot of cabbage. A badly infested field. After H. L. Russell. 



following list of plants has been reported as sufferers from this 

 rot : cauliflower, kohl rabi, kale, brnssel sprouts, broccoli, col- 

 lards, turnips, rutabagas, winter radish and still others. Ruta- 

 bagas and their allies are not so commonly nor so severely at- 

 tacked as the cabbage group. 



The effect of the disease is first seen at the edge of the 

 leaf. The lower leaves are most commonly invaded but all of 

 the leaves of a head may be attacked at once. The bacteria 

 work downward along the veins of the leaf to the stem of the 

 plant. The invaded veins turn black. From the stem the bac- 

 teria spread outward again with great rapidity. The attacked 



