984 MICROBIAL DISEASES OF PLANTS 



PATHOGENESIS. Pathogenic for cauliflower, cabbage, and turnips; 

 a soft rot can be produced in a large variety of vegetables under labora- 

 tory conditions by pure culture inoculations. 



CONTROL. Complete destruction of diseased crops by burning and 

 crop rotation are to be recommended. 



Harding and Morse,* from their extensive comparative studies of 

 microorganisms producing soft rots of vegetables make Bacillus oleracecR 

 of Harrison identical with B. carotovorus of Jones. 



SOFT ROT OF CALL A LILY 



Bacillus aroidecz Townsendf 



A soft rot of the calla lily, distinct from other soft rots, is scattered 

 over the calla-growing sections of the United States. The disease starts 

 at the top of the corm and causes a rotting of the plant at or just below 

 the surface of the ground. As a result the leaves and flower stalk turn 

 brown and fall over. The healthy corms are white, but the infected 

 ones are brown, soft and watery. 



It is believed that the causal organism lives in the soil and enters the 

 plants through wounds. The disease is undoubtedly spread from one 

 locality to another by shipping slightly diseased corms. 



As a means of control, only sound corms should be used, and the 

 soil in the calla beds should be changed every three to four years. 



SOFT ROT OF CARROT AND OTHER VEGETABLES 



Bacillus carotovoms Jones 



A number of the cultivated plants of the north temperate zone, 

 notably those grown for their root crops, suffer, at times, from a bac- 

 terial rot caused by a liquefying bacillus. Although probably as widely 

 distributed as any microorganism parasitic upon plants, it was not de- 

 scribed until igoi.J 



Bacillus carotovorus is a wound parasite which invades the inter- 

 cellular spaces, dissolving the middle lamellae and poi tions of the inner 



* See footnote, p. 985. 



f Townsend, C. O., Bull. 60, Bur. Plant Ind.. U. S. Dept. Agr., 1904. 



t Jones. L. R., "A Soft Rot of Carrot and Other Vegetables," I3th Report Vermont Exp. 

 Station, p. 299, 1901. 



