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A NEW PHOMA DISEASE OF THE SWEDE. 



The disease of which I am now treating is, I believe, one 

 which has hitherto escaped notice, and it has not been de- 

 scribed as occurring in this country ; but I have reason to 

 believe that it is not at all uncommon in the North of England. 

 Some years ago, in the winter of 1896-7, I first noticed the 

 appearance of this parasitic attack of the swede at Corbridge. 

 It has since occurred at intervals in other neighbouring 

 localities, and last autumn I found it on the experimental 

 plots at the Northumberland Experimental Farm at Cockle 

 Park, on some of which it had obtained considerable hold. 

 At Cockle Park the percentage of roots attacked varied in 

 the different fields ; where the disease was most noticeable 

 some of the rows had as many as 25 per cent, attacked, while 

 in other fields scarcely one per cent, was found. 



The disease, when fairly advanced, is easily recognisable 

 by certain pale straw-coloured to brownish patches con- 

 trasting strongly with the ordinary colour of the root, and 

 by the large, dry cracks, some penetrating deeply into the 

 flesh, which form a very prominent characteristic (Fig. 1). 

 The natural purple colour of the swede is destroyed and 

 replaced by these discoloured patches, which form areas 

 of depression on the surface of the root ; and surrounding the 

 lighter central portion of the patch is a narrow border of 

 darker metallic green, which shades into a dark purple 

 merging gradually into the normal tone of the still healthy 

 tissue. Numerous small spots of the deep purple-green 

 encircling a central lighter spot indicate the commencement 

 of attacks (Fig. 2 A). These gradually enlarge, the attack 



