CABBAGE ROT 349 



only known method of control is by the removal of all dis- 

 eased branches as the symptoms appear. The cut should 

 be made twelve to fifteen indies below' the last visible sign 

 >f tin- disease. The diseased wood should be burned. Care 

 should be exercised not to spread the infection through the 

 priming-knife or saw. 



Cabbage rot. Of the class of bacterial diseases known as 

 the rots, the black rot of the cabbage and related plants is 

 most common and important. The first symptom is the 

 appearance of yellow or brown areas near the margin of the 

 leaf. The organism enters the tissues through the water 

 pores on the edge of the leaf, and spreads along the ribs of 

 the leaf, ultimately reaching the main stem of the plant in 

 many cases. It causes the death and softening of the tis- 

 sues. Invasion by other forms readily occurs in the 

 broken-down tissue, with the result that the entire head 

 ultimately is destroyed. The affected ribs are blackened, 

 and on cutting across the infected stem one can see the 

 blackened ends of the fibrous strands (the fibro-vascular 

 bundles). 



The organisms may also enter the plant through wounds 

 on the roots, such as are made when the young plants are 

 transplanted. It has been shown that the organisms may be 

 on the seed, and thus the soil of the seed-bed infected with 

 the organisms, which await a favorable opportunity to pene- 

 trate the plant. 



Preventive measures must consist of disinfection of the 

 1 and rotation of crops. 



Rots caused by other bacteria occur in carrots, sugar- 

 beets, muskmelons, and hyacinths. 



Wilts. The wilts of the cucumber, muskmelon, squash, 

 and pumpkin are widespread in the eastern half of the 

 United States. The disease is characterized by a wilting 

 of the vine, without any visible external cause. The leaves 



