30 Letters on the Diseases of Flants. 



The amount o£ damage done by this disease is variously estimated, but is 

 on the whole, I think, exaggerated. According to my observation it causes 

 much less loss than Melanose, though in some orchards the Black Spot pre- 

 dominates, and in such cases is responsible for much damage, 



Fig. 34.— Oranges attacked by so-called " Black Spot." The diseased spots occur as more or, less isolated 

 roiindish svmken, at first dark-colom-ed spots, tlie interior portion of which, however, at maturity 

 is lighter coloured, with small dark spots (imstules) at the points where the spores break forth. 

 These five oranges show no other disease all the various defects seen on the skin are due to Black 

 Spot. 



'Remedies. 



1. Laboratory observations show that even dilute Bordeaux mixture poisons 

 the spores of the fungus causing Black Spot. This points once more to the 

 use of this well-known mixture as a preventative. From the nature of the 

 fungus it it^ plain however that the spray can act only as a preventative, and 

 therefore the treatment should be begun early, and continued right through 



