Bacterial Diseases of Plants. 237 



and full of sap. By midsummer the progress of the 

 disease is checked by natural causes. The bacteria may 

 pass the winter in the affected tree and with the advent 

 of warm weather begin to grow once more. It is claimed 

 that trees in a thrifty condition and that are making a 

 large amount of growth are more susceptible to attacks 

 than trees under less favorable conditions. 



Prevention. Since the bacteria are protected by the 

 bark nothing can be done to destroy them by the use of 

 spraying solutions. The only method of preventing the 

 spread in the tree is by the removal of all affected 

 branches which should be cut off several inches below the 

 last visible signs of disease as the bacteria extend beyond 

 this point. The diseased wood should be burned, other- 

 wise the bacteria may be carried to still healthy trees by 

 insects. Care should also be exercised not to spread the 

 disease through the pruning or grafting knife. 



Cabbage rot. The cruciferous plants as cabbage, 

 cauliflower, turnips, etc., are subject to rots caused by 

 bacteria. The most common method of infection of the 

 plant is through the small water pores on the edge of the 

 leaf. They may also enter through wounds such as are 

 made on the roots at the time of transplanting. It has 

 been shown that the seed may be infected; in this way 

 the soil of the seed bed is inoculated with the bacteria 

 and opportunity is offered for infection of the young 

 plants. The bacteria will persist in the soil of a field or 

 seed bed for a number of years, hence it is advisable not 

 to use the same^ field or bed when the disease has ap- 

 peared. Seed may be rendered free from the cabbage rot 

 bacteria by soaking it in a one to one thousand solution 

 of corrosive sublimate for fifteen minutes. 



The disease appears first in the form of brown spots on 



