BLACK ROT OF CRUCIFEROUS PLANTS. 



(Synonyms: Dry rot, Brown rot, Stem-rot, Black stem, Black vein.) 



DEFINITION. 



This is a specific communicable disease of the cabbage and its allies, usually requiring, 

 except in seedlings, several months for the crippling or entire destruction of the plants. 

 When not accompanied by other bacteria, the signs are dwarfing or one-sided growth, 

 yellowing, gradual loss of leaves, and a brown stain of the vascular system, which is the 

 primary seat of the disease (plate 17). Closed bacterial cavities are common in the bundles. 

 Frequently, secondary parenchyma-rots set in and then the destruction of the plant is 

 more rapid, and its appearance is changed. 



HOST-PLANTS. 



This disease has been observed by the writer in cabbages (Brassica oleracea f. capitata), 

 cauliflower (Brassica oleracea f. hotrytis), collards (B. oleracea f. gemmijera), kale (Brassica 

 oleracea f. acephala), kohlrabi (Brassica oleracea f. gongylodes), rape (Brassica napus), 

 turnip (Brassica ra^a), rutabaga (Brassica campestris) * charlock (Brassica sinapistrum) , 

 and radish (Raphanus raphanistrum) . With exception of collards and charlock the writer 

 has inoculated it successfully into all of the above plants, and repeatedly into cabbages. 

 It is the same organism in all of these species and varieties. On some of these plants 

 numerous infections have been obtained also by other persons. The writer has produced 

 the disease also in the black mustard (Brassica nigra) by pure culture inoculations. Very 

 likely other cruciferous plants will be found to be subject to this disease. 



The following species were inoculated by the writer by needle-punctures in stems and 

 leaves, but did not contract this disease : Hyacinthus albulus, Solanum tuberosum, Cucumis 

 sativus, Matthiola annua, Nasturtium officinale, and Nasturtium armoracia. These experi- 

 ments should be repeated on Matthiola and on the Nasturtiums, particularly on N. armor- 

 acia, because the latter plant is known to be subject to a disease of the crown and root which 

 results in brown-stained vessels and cavities of considerable size (Sorauer) and because 

 Faber, of Berlin, has recently reported its occurrence in stock (Matthiola). The writer has 

 himself seen this disease of horse-radish in the United States, but not under conditions that 

 made it possible to determine its cause. 



GEOGRAPHICAL DISTRIBUTION. 



This disease has been observed in many parts of the United States. It occurs in Vermont, 

 New York, New Jersey, Pennsylvania, Maryland, Virginia, North Carolina, South Carolina, 

 Alabama, Florida, Kentucky, Ohio, Indiana, Illinois, Michigan, Wisconsin, Minnesota, Iowa, 

 Nebraska, Colorado, Texas, Arizona, Washington State, and California(?). In 1904 it was 

 observed by the writer in cabbage, cauhflower, and kohlrabi at Miami in Southern Florida, 

 and what seemed to be the same thing was found the same year in cabbages planted in gardens 

 at Baracoa in the extreme eastern end of Cuba (latitude 20° 35'). It has been reported also 

 from Porto Rico. The disease was first described from the United States, but it has since 

 been shown to occur in various parts of Europe, e. g., in England, Germany, France, Swit- 

 zerland, Denmark, Holland, Austria and Russia (Frank, Harding, Appel, Hecke, van Hall, 

 Potter, Brenner, etc.). The writer searched in vain for it in southern Italy in 1906. The 

 gardens of cauliflower about Naples showed no trace of it. Nothing is known as to its 

 occurrence in other parts of the world, except that Kirk has recently reported it from New 

 Zealand. The disease is to be looked for wherever plants of this family are cultivated. 



*The preceding 8 forms are closely related and are all classed under B. campestris L. by some authors. 

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