21 
ANTHRACNOSE OR “BLACK SPOT” 
(Pkonia citricarpa n. sp.) 
This is a disease which has not been met with in Victorian 
orchards, but it is quite common on the fruits sold in Melbourne 
and suburbs. It is very common on oranges, mandarins, and 
lemons imported from Sydney, where it is very prevalent, and 
also in surrounding districts. It spots the fruit, and when -well 
developed renders it unsightly and almost unsaleable—lowering 
its market value as well as interfering with its keeping quality. 
I find that such fruits soon become rotten and fall a ready prey 
to “ Blue Mould,” &c,, so that all such should be rigidly excluded 
from shipments to England. 
Symptoms .—The spots are round and sunken and of a dark- 
brown colour, at first whitish or greyish towards the centre, but 
ultimately they may become one uniform tint. They are either 
isolated or run together and vary in size from one-eighth of an 
inch or less up to large irregular confluent brown patches of 
half-an-inch or more. In the centre of these spots there soon 
appear a number of minute black dot-like pustules, just visible 
to the naked eye, and which are the cases containing the repro¬ 
ductive bodies or spores. (Plate II.) These pustules have a 
minute opening at the top to allow the escape of the spores, 
which may be wafted by the wind or carried by animals, and 
thus the disease is rapidly and widely spread. 
Effects .—In certain districts of New South Wales it causes 
considerable damage to the orange crop, and lemons seem to be 
very subject to the disease. It is found on still green fruit, but 
it spreads most rapidly wheu the fruit is ripe, the pustules 
developing best under these conditions and producing their 
innumerable spores. The disease readily spreads from fruit to 
fruit, and from tree to tree, and when badly affected the fruit 
drops and is useless. It is sometimes spoken of slightingly, as 
if it were only a skin disease; but its effects are much more far- 
reaching, for not only does it spread to apparently clean fruit in 
the case, but it induces rottenness and decay. It is a matter of 
common observation that such fruit does not keep, and if clean 
and unclean fruit, plucked at the same time, is kept under similar 
conditions, the rapid decay of the spotted fruit is very marked. 
Cause .—It is rather surprising that a disease which seems to be 
so prevalent in New South Wales orchards should have been so long 
neglected and its true cause not investigated. It is a compara¬ 
tively easy matter to determine the fungus when the fructification 
is so common in the shape of the minute black pustules. The 
so-called “ practical man ” usually considers the scientific deter¬ 
mination of disease-causing fungi as unnecessary, and not likely 
to help him in any way in combating disease. But when it is 
