* 



[Crown Copyright Reserved 



ROYAL BOTANIC GARDENS, KEW. 



BULLETIN 



OF 



MISCELLANEOUS INFORMATION. 



Nos. 6&7] 



[1919 



XVI.— SILVER LEAF DISEASE.* 



Stereum purpureum, 



J. Bintner. 



(With Plate.) 



I . — Introduction . 



" Silver leaf " is notorious not only for the serious damage 

 which it causes to fruit trees but also for the controversies con- 

 cerning the nature of the disease. 



The first observations were made by Prillieux (1) 1885 in France, 



and published under the title of " Le Plomb des arbres fruitiers." 

 He considered the leaden colour of the leaves to be the result 

 of the presence of large air spaces between the epidermal and 

 palisade cells; he also noticed larger epidermal cells in the 

 infected leaves than in the normal leaves. In 1886 Sorauer (2) 

 referred to the " Milchglanz " of fruit trees, and again Aderhold 

 (3) in 1894, mentioned it as occurring in Germany. Both these 

 authors considered " Silver leaf " of fruit trees as of non- 

 parasitic character. This theory however became very im- 

 probable on the discovery, made in England by Percival (4), who 

 in 1901 applied the name " Silver leaf " to the disease, that fun- 

 gal hyphae existed in the wood of silvered plum-trees. Successful 

 inoculation experiments by Percival, who proved that 

 silvering could be caused by the fungus Stereum purpureum, 

 did not however convince all his contemporaries. Massee (5), for 

 instance, still attributed the disease to some physiological dis- 

 turbance. Delacroix (6) erroneously -rates that Percival had 

 described Stereum hirsutum as the cause of silvering, and even 

 adds: "Malgre P affirmation de cet auteur (Percival), nous ne 

 pouvons, jusqu'a plus ample informe, admettre de telles con- 

 clusions. " Blackmore (T) in commenting on this disease in his 

 report on Xew Zen land diseases, states that " Silverblight 

 certainly is becoming very prevalent in a number of orchards 

 in North Otago and elsewhere. Often where ^ fruit trees are 

 making succulent growth it spreads rapidly, killing trees within 



* This research was carried out in the Laboratories of the "Department 

 of Plant Physiology and Pathology. Imperial College of Science and 

 Technology, South Kensington. Mr. Bintner was formerly a Sub-Foreman 

 in the Koyal Botanic Gardens. — En. 



(480.) Wt. 158—829. 1,125. , 9/19. J. T. & S., Ltd. G. 14. Sch. 12. 



