VIF CABBAGE AND RELATED PLANTS 233 



"club root," and "clump foot." The organism gains 

 entrance through the roots, causing them to become 

 more or less enlarged and knotty, and then to undergo 

 a decay. This enlargement frequently begins in the 

 seed beds. The organism is very low in the scale of 

 plant life and attacks a great many other cruciferous 

 plants, in many cases becoming very destructive. 

 The malformations of the roots frequently cause the 

 disease to be confused with the nematode root knot, 

 but an examination with the microscope will readily 

 detect the true cause. It can be controlled to some 

 extent by the selection of healthy plants, burning the 

 diseased plants and rubbish, heavy applications of lime, 

 and the rotation of crops. 



Cabbage Rot. This disease is due to Pseudomonas 

 campestris, (Pam.) Smith, and is also widely distributed 

 throughout both tropical and temperate zones. It 

 causes a dwarfing of the plants and a one-sided growth 

 of the heads, or even prevents the formation of a head. 

 It frequently causes the death of the entire plant. 

 Occasionally the heads rot and drop off. The organism, 

 which is a bacterium, enters the plant through the 

 small water pores along the margin of the leaf. The 

 organisms are very abundant, and travel rapidly down- 

 ward along the fibre-vascular bundles to the stem, and 

 thence outward through the other leaves of the plant. 

 The diseased leaves get yellow, the veins become black, 

 and finally the entire structure dies and falls off. This 

 organism also attacks the turnip, and many other 

 cruciferous plants. No successful treatment is known, 

 but the treatment given for club root would no doubt 

 be helpful in controlling the pest. 



Other Diseases. The cabbage and related plants 

 suffer from a number of other diseases, such as 

 Rliizoctonia stem rot, downy mildew caused by 

 Peronospora parasitica, (Pers.) De Bary, white rust 

 caused by Cystopus candidus, (Pers.) Lev., a soft rot 

 caused by Bacillus carotovorus, Jones, and a rot caused 

 by Sclerotinia libertiana, Fckl. Our information 



