122 



Although the disease is most destructive 

 to plum trees, it is not confined to them, 



and the apple, cherry, damson, apricot, 

 currant and gooseberry are liable to infec- 

 tion. It also occurs on such trees as labur- 

 num and Portugal laurel. 



Sometimes the scions of recently grafted 

 apple trees show silvered leaves one year 

 and later become normal. It is advisable 

 therefore, in such cases, not to destroy the 

 scions immediately; if, however, they suc- 

 cumb, they should be removed and burnt 

 without delay. 



GoosEBEEEY Mildew. 



Gooseberry bushes are liable to infec- 

 tion by two powdery mildews. One of 

 these, known as the American Gooseberry 

 Mildew {Sphaerotheca mors-uvae), is the 

 most troublesome fungus pest that the 

 gooseberry grower has to contend with. 

 It makes its appearance in spring, often 



Fig. 7. — The Silver Leaf Fungus, Stereum pur- 



pureum, on a dead branch oi a Victoria Plum 



Tree. 



Fig. 8. — Gooseberries, showing the brown winter 

 stage of the American Mildew. 



in May, and even sometimes in April, as 

 a whitish powder on the young leaves. 

 As the shoots elongate the mildew grows 

 over the tips and may extend downwards 

 along the surface of the shoots for 

 several inches. The fungus later becomes 

 darker in colour, and eventually forms 

 a dense, dark-brown, felted film, covering 

 the affected parts. 



When the berries are formed they 

 too become attacked; here again the 

 fungus is first seen as white pow- 

 dery patches, which later become brown 

 and felted (Fig. 8). If the berries 

 become infected when quite small they 

 may become completely covered with the 

 fungus, and in consequence are prevented 



