344 



Minnesota Plant Diseases. 



Allowing these plants to remain on the field only increases the 

 danger. It has been found possible and profitable to attempt 



Fig. 177. — Black rot of cabbage. Cabbage heads, apparently sound, are attacked by the rot. 

 The progress of the disease is seen in the blackened parts of the stems and leaves. 

 After H. L. Russell. 



a control of the disease in its early stages by a close inspection 

 of the young plants and by picking off the infected leaves. 



Fig. 178.— Black rot of cabbage. A cabbage leaf showing the manner of infection. Dis- 

 eased area (B) unshaded except the blackened meshes of veinlets. A. A hole eaten by 

 insects. The disease was introducd at this point and spread backward to the main rib. 

 C. Blackened veinlets affected by the disease. D. Water pores of the cabbage leaf 

 through which the disease germs gain a foothold, producing marginal infection. After 

 H. L. Russell. 



