302 PLANT DISEASES 



and after the buds have expanded, with dilute Bordeaux 

 mixture at intervals of ten days. 



Smith, Card. Chron., vol. xxiv. p. 51, figs. 

 Massee, Brit. Fungus-Flora, vol. iv. p. 281. 

 Smith, Journ, Mycol., vol. v. p. 123. 

 Arthur, Fourth Ann. Rep. N. York Agric. Expt. Station, 

 p. 254 (1885). 



DEMATIEAE 



APPLE SCAB 

 (Fusidadium dendriticum, Fuckel.) 



The most injurious of fungus parasites attacking the 

 apple, in many instances rendering unsaleable half or more 

 of the entire crop, in addition to doing permanent injury to 

 the trees. It was at one time considered that the disease 

 was confined to the fruit, but it is now well known that the 

 leaves and young shoots are also attacked ; in fact, as a 

 rule the fungus first appears on the leaves under the form 

 of small, roundish, dark spots, mostly on the upper surface. 

 These spots soon increase in size, and run into each other, 

 forming large, irregularly shaped, blackish blotches; and 

 when conditions are favourable for the growth of the 

 parasite, the leaves are frequently killed while quite 

 young. 



The dark-coloured mycelium spreads in the leaf or fruit 

 between the cuticle and the epidermis, the cuticle being 

 eventually ruptured, and myriads of very short branches 

 protrude, each bearing a conidium at its tip. The disease is 

 extended throughout the season by means of these conidia. 



