Minnesota Plant Diseases. 



343 



FIG. 175. Black rot of cabbage. Artificial infection of cabbage plants. The plants in the 

 center (2), and on the right (1), were inoculated six weeks previously with bacteria. 

 The plant on the left (3) was not inoculated and is therefore unaffected. After H. L. 

 Russell. 



leaves wilt, turn yellow and finally dry up, when 

 they become somewhat papery in appearance. 

 The disease may appear in stored cabbage in 

 which the heads may be entirely destroyed. 

 Other rots assist in transforming the diseased 

 heads into a rotting, bad smelling mass. Cab- 

 bage for storage should therefore be carefully 

 inspected and where any blackened veins in the 

 leaves show should be rejected. The bacterium 

 gains entrance either through wounds or 

 through the water-pores at the edge of the leaf, 

 weather assists in the spread of the disease. 



Refuse matter should be removed from the field. Rotation 

 of crops will assist in ridding, in part at least, the soil of the 

 disease. Low, damp soils should be avoided and if irrigation ; s 

 practiced reduction of moisture will prevent the formation of 

 water drops at the water-pores on the leaves, and thus reduce 

 the number of chances of infection. Diseased plants can read- 

 ily be detected by breaking off the lower leaves and examining 

 the stalk. If the fibres of the leaf-stalk are blackened, the plant 

 is diseased and should be rooted out and entirely destroyed. 



FIG. 176. Black 

 rot of cabbage. 

 Bacteria highly 

 magnified. After 

 H. L. Russell. 



Rainy, moist 



