Vegetable and Field Crops 



167 



resulting in complete loss. The bacteria may travel upon 

 seed from diseased localities, infect the young plants, and 

 initiate an attack in a new locality. Plants shipped across 

 the country may also carry infection. 



The disease may be carried from field to field in any 

 plant part or in infected soil, upon tools, feet, etc., and espe- 

 cially in manure that has become infected by the use of 



Fig. 90. — Cauliflower affected with black-rot. 

 Original. 



diseased plants as feed. To avoid carrying contamination 

 to near-by fields all the precautions suggested under soil 

 diseases must be employed. 



With infested land the only recourse is such crop rotation 

 as will avoid the planting of a susceptible crop for a period of 

 several years. Just how long the bacteria can remain alive 

 in the soil is not known. In practicing crop rotation for 

 elimination of this pest all cruciferous weeds, mustard, shep- 

 herd's purse, etc., should be avoided, since they are sus- 



