25 
SOOTY MOULD OF ORANGE AND LEMON. 
(Capnodium citricolum , Me Alp.). 
The disease of Sooty Mould has been known since the begin¬ 
ning of the century, chiefly in southern Europe, and now wherever 
citrus trees are grown. It passes under various common names 
in different countries, such as “ Morfea,” “ Fumago, ,, “ Nero,” 
and u Mai di cenere” in Italy, the latter name referring to the 
as hy-grey incrustation, which afterwards becomes black ; “ Russ- 
thau ” or Soot-dew in Germany ; “ Sooty Mould ” in Florida ; 
and “ Fumagine,” “Black Mildew,” “Black Blight” among 
ourselves. It is likewise often called “ Smut,” from its appear¬ 
ance, but does not belong to that division of fungi which includes 
the true Smuts. And the scientific names applied to it have been 
equally varied, for the fungus assumes a variety of different forms, 
to which different names have been given. In fact, this u Sooty 
Mould ’ affords a very good illustration of what has been called 
Polymorphism, the same fungus appearing under different guises 
at different stages of its development. It is one of those diseases 
which seemingly does not do much damage, but which in the 
aggregate is very injurious. It is dependent on certain insects 
for its spread, and as these multiply it also increases. Trees are 
sometimes met with largely covered with the sooty fungus, and, 
as it spreads rapidly, every precaution should be taken to arrest 
its progress. 
Symptoms .—It occurs on the living leaves, particularly on the 
upper surface, but it may also appear more or loss on the under 
surface. It is also found on the branches, as well as on the fruit, 
usually on the upper or stem end as the fruit hangs down 
(Plate III., Fig. 1). It forms black soot-like incrustations, peel¬ 
ing ofl in flakes, like a continuous membrane of black tissue- 
paper. It is entirely superficial, not penetrating the tissues in 
anyway. I here are all sorts of gradations in the nature and 
extent of the fungus. It may appear at first just like a sprink- 
liug of dust on the leaf (in fact, growers do confound it with 
dust), then of a dark muddy grey, peeling off as a thin papery 
layer, and finally as a sooty crust, soiling the fingers when 
nibbed. At times there is a considerable admixture of dust with 
the filaments, and then it is usually checked in its development. 
I he depth of the colour is evidently largely influenced by the 
relative amouuts of more or less colourless and coloured hyph®, 
both of which are usually present. 
Effects .—This fungus does not produce any marked injury to 
the tree at first; as, when the “ Sooty Mould ” is removed from a 
leaf, the surface beneath is often as green and glossy as a healthy 
one. The injury is rather of a mechanical nature, and, combined 
