33 
“BLACK SCURF” OF CITRUS FRUITS. 
* (Coniothecium scahrum , n. sp t ) 
There is a scurfincss often observed on Citrus fruits, which may 
cover a smaller or larger area of the skill, caused by this black, 
soot-like fungus. It might readily bo mistaken at first for the 
“ Sooty Mould,” and even microscopically it resembles a stage of 
it, but it is distinguished by not being necessarily accompanied or 
preceded by scale insects, and chiefly by the skin disease it pro¬ 
duces. The Sooty Mould may peel off in flakes or be easily 
rubbed off, leaving the skin quite unbroken and uninjured, except 
possibly rendering it a little paler in colour ; whereas in this case 
the surface of the skin is cracked and ultimately becomes scurfy. 
Symptoms .—The appearance on the fruit is very characteristic. 
It first begins as little black depressions, causing the skin around 
for a considerable area to become of a yellowish-green. Then it 
gradually spreads to form large sooty-black patches, the epidermis 
cracking all over into minute irregular areas. Finally the black 
masses of conidia are detached in fine flakes, and t here is a dirty- 
grey, scurfy, depressed patch left to indicate where the fungus 
had been. 
Effects .—As in the case of so many other skin-diseases, it is not 
the damage actually done to the fruit, nor the unsightly appear¬ 
ance produced by it, which is most important, but the after effects, 
causing the fruit to be more liable to decay, and thus interfering 
with its keeping qualities, as well as to be more readily attacked 
by oilier parasites. 
Cause .—The black soot-like substance is mainlv composed of 
reproductive bodies, which are composed of mulberry-like clusters 
of brown cells. The cracking of the skin is caused by the 
> filaments of the fungus bursting through to produce their conidia 
at the surface, and small patches of the skin aro readily detached 
bearing these bodies with them. This causes the roughness of 
the skin and the various symptoms already described. 
L Treatment .—No actual experiments have been carried out as to 
treatment, but general healthy growth should be encouraged. As 
this is a form of scab, the recommendations given for dealing 
with it should be followed. 
3316. 
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