VEGETABLE AND FIELD CROPS 



211 



CABBAGE 



Black rot (Pseudomonas campestris (Pamm.) E. F. 

 Smith). — Not only does black rot destroy the crop of the 

 year, but since its causal germ remains in the soil, it seri- 

 ously endangers, if it does not quite prohibit, the subse- 

 quent use of the same 

 field for susceptible 

 crops. Its damage in 

 a single season in two 

 counties in Wisconsin 

 was estimated at be- 

 tween $50,000 and 

 $60,000. A large per 

 cent of the damage to 

 cabbage in storage is 

 also attributable to this 

 disease. Cabbage, kale, 

 rape, broccah, kohl- 

 rabi, Brussels sprouts, 

 collards, turnips, ruta- 

 bagas, radish, black 

 mustard, charlock, and 

 other members of the 

 cress family are affected. 



It was first noted in 

 1895 ' in Wisconsin, and has since proved very disastrous 

 in its effects in practically all sections of the United States. 



The first sign of the disease appears upon the edges of 

 the leaves as a blackening of the veins. The affected region 



' Proc. Amer. Assoc. Adv. Sci. 1895, p. 93; cited in Wis. Agr. Exp. 

 Sta. Bui. 65, p. 10, February, 1898. 



Fig. 95. — Cabbage leaf shoi\ing an incipient 

 stage of blaclc rot. Tlie disease, which enters 

 at the ends of the veins, is progressing toward 

 the base of the leaf. After Stewart and 

 Harding. 



