SILVER-LEAF DISEASE. 



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SILVER-LEAF DISEASE. 



[So widespread and disastrous in its effects, especially upon stone- 

 fruit trees, is the silver-leaf disease, and so many requests for infor- 

 mation concerning it are received, that the Council of the Royal 

 Horticultural Society has caused the following account of it to be 

 drawn up for the information of the Fellows, and it appeals to them 

 to do their best to check the spread of the disease by adopting the 

 measures recommended.] 



Symptoms of the Silver-leaf Disease. — Except in the case of ever- 

 green trees, silver-leaf is not easy to detect in winter. In summer 

 the curious leaden or silvery appearance of the foliage of the diseased 

 parts of trees contrasts conspicuously with the normal green of the 

 healthy foliage and renders the disease easy of detection. The diseased 

 leaves are usually of normal shape and size. If a diseased leaf be 

 examined carefully it will be found that the upper skin (epidermis) 

 readily separates from the green cells beneath and is easily peeled off. 

 The wood of the diseased branch is stained brown to a greater or less 

 extent. The simultaneous presence of these three symptoms serves 

 to separate the common true silver-leaf from those rarer cases where 

 a somewhat similar silveriness of foliage is produced by some less 

 serious cause. In false silver-leaf neither of the last two symptoms 

 is as a rule present. The silver tinge of the leaves is due to the 

 presence of large air-spaces beneath the epidermis, where the latter 

 has become separated from the green cells which form the bulk of 

 the leaf. 



The Serious Nature of the Disease. — Trees or branches attacked by 

 the silver-leaf disease may live for some years, but they rarely flower 

 or fruit, or when they flower abundantly the fruit is inferior. They 

 very rarely recover their health, and eventually die prematurely. 

 In bad cases death may occur within a year. When dead the branches 

 are a menace to all other fruit-trees in their neighbourhood. 



Trees Liable to the Disease. — The disease is most frequent upon 

 trees belonging to the plum and cherry tribe. It is doubtful whether 

 any variety of plum is proof against its attacks, although it is less 

 frequent upon the ' Pershore ' or ' Egg Plum ' than upon most. 

 ' Victoria ' is the most frequent victim, but ' Pond's Seedling ' is 

 often attacked. Sweet and acid Cherries, Peaches and Nectarines, 

 Apricots, Almonds, Sloe, Prunus japonica, and P. lusitanica (Portugal 

 Laurel) are known to be attacked, the last very commonly. In 

 addition, it is on record that the following have all been attacked— 

 Apples (e.g. ' Gascoigne's Scarlet,' ' Newton Wonder,' ' Lord Gros- 

 venor,' ' Bramley's Seedling,' ' Lord Suffield '), Pears, Pyrus torminalis, 



