CHAPTER IX 



LEAF AND SEEDLING DISEASES 



The larch needle-cast (SpTtaerdla laricina). Meria laricis. Hypo- 

 dermella laricis. The larch needle-rusts : Melampsoridium betulinum, 

 Melampsora tremulae, &c. Damping-off diseases : Phytophthora omnivora ; 

 Fusoma parasiticum. 



LEAF diseases of the larch are less harmful than the 

 needle diseases of other conifers on account of its deciduous 

 habit. In pines and spruces, in which the leaves function 

 for several years, defoliation is a very serious matter, and 

 in consequence the pine leaf -cast is one of the most dreaded 

 diseases that infect trees. Not so with the larch, and 

 a comparison of the bulk of literature published on the 

 needle-casts of the larch and pine respectively justifies the 

 supposition that Hartig's assessment of the importance of 

 the former was pessimistic. Furthermore, those diseases 

 which have been described as frequent and dangerous on 

 larch needles in Germany and other continental countries 

 are very infrequent in Britain. Indeed, some of them have 

 never been recorded here, and their inclusion in this book 

 is justified only as a warning to foresters of diseases which 

 may spread to us from across the North Sea. There is no 

 reason to think that our insular climate will render us 

 immune from any of these pests, and it may be noted that 

 Chrysomyxa abietis has already spread to the spruce needles 

 of Scotland 1 and the north of England, 2 although until 

 recent years our woods were entirely free from this fungus. 



The larch needle-cast : Sphaerella laricina (R. Hartig). 

 This fungus causes the most serious larch-needle disease that 

 is known in Europe. It was described by Hartig in a very 

 interesting article published in 1 895, and the folio wing account 

 is derived entirely from this source. The needle-cast was first 



1 Somerville (1911, 1915, 1917), Cowan (1915). 2 Hiley (1917). 



