CHAPTER IX 
LEAF AND SEEDLING DISEASES 
The larch needle-cast (Sphaerella 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} and the north of England,? 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 1895, and thefollowing account 
is derived entirely from this source. The needle-cast was first 
1 Somerville (1911, 1915, 1917), Cowan (1915). ® Hiley (1917). 
