Brown-rot of Swedes. 



3i7 



Harding * have brought out the fact that the germs of the 

 disease have become so abundantly and widely distributed 

 that it has been found impossible to discover any means 

 of checking it. Hecke f has also described the same attack 

 as widely distributed in Austria, destructive in gardens in the 

 neighbourhood of Vienna and in various districts in the 

 Tyrol. Harding X mentions it in widely separated localities in 

 Europe. 



Smith has shown by experiments that the natural method of 

 infection is chiefly through the water-pores of the leaves and also 

 through the agency of slugs and caterpillars. I have always 

 observed the infection to have commenced through some injury 

 to the root. Many parasites, both among fungi and bacteria, 

 have no power to penetrate the hard outer rind of the sound 

 root, and only find an entrance when the way is opened by 

 injury inflicted by some agency such as that described. The 

 amount of harm done by slugs, snails and caterpillars, and 

 other destructive larvae in the soil is incalculable, and it would 

 be well if more could be done to eradicate such pests before the 

 crops are sown. 



The attack being confined to the Cruciferae, crops belonging to 

 this order should not follow each other for several years, the 

 decaying plants ought not to be given to stock, nor should the 

 manure from animals fed on these plants be used for crops 

 liable to the infection. A serious outbreak of brown-rot has 

 been traced to infected manure. If also the rotting plants are 

 allowed to remain in the field the germs infect the soil and are 

 ready to infest the succeeding crop. 



It may be useful to add that the disease above described is 

 easily recognisable on cabbages. There is the same blackening of 

 the tissues along the path of the vascular bundles. Black spots 

 appear upon the margins of the leaves and the discolouration 

 extends along the veins. If the leaf-stalk is cut transversely 

 the veins occupied by the bacteria can be seen as black dots. 



* Combating the Black-Rot of Cabbage by the Removal of Affected Leaves. 

 New York Agricultural Experiment Station. Bulletin No. 232, 1903. 



t Die Bacteriosis des Kohlrabi. Zeitschrift fur das landwirthschaftliche 

 Versuchswesen in Oesterreich, 1902. 



+ Die schwarze Faulnis des Kohls ttnd verwandter rflanzev. Centralblatt 

 fur Bakteriologie u.s.w. Abt. II., Bd. VI., 1900. 



