BLACK SPOT OF CITRUS FRUITS CAUSED BY PHOMA 
CITRICARPA McALPINE 
By H. Atherton Lee 
Mycologist, Bureau of Science, Manila 
FOUR PLATES 
Black spot of citrus fruits was described by McAlpine 1 from 
Australia, in 1899. McAlpine observed the presence of 
a fungus uniformly associated with this black spotting and 
described it as Phoma citricarpa, the cause of the disease. No 
isolations of the fungus or reinoculations are reported in his 
description. The purpose of the present paper is to present 
data of such isolation and reinoculation experiments with Phoma 
citricarpa and also to record further knowledge as to the distri- 
bution of the disease. In calling attention to the disease and 
its distribution, it is also hoped that some assistance will be 
rendered to growers in the citrus-producing countries where it 
does not yet occur, since with a full knowledge of its characteris- 
tics it can be easily excluded. Photographs are presented to 
facilitate the recognition of the disease. 
DESCRIPTION OF THE DISEASE 
The spots are found only on the fruits; the leaves and twigs 
have not been affected, in the experience of the writer. The 
disease has been observed upon fruits of the sweet orange ( Ci- 
trus sinensis) and the mandarin orange ( Citrus nobilis) . Pum- 
melos {Citrus maxima) and calamondins {Citrus mitis), although 
seen in countries where the disease is common, as yet have not 
been found to be affected. Lemons are reported by McAlpine 
to be affected. Data are not yet available as to the other species. 
Small, reddish-brown spots appear on the surface of the fruit; 
with increasing age these spots turn darker, becoming sometimes 
entirely black. The spot may be only 1 or 2 millimeters in diam- 
eter, but with time the area may spread to from 7 to 9 milli- 
meters in diameter. As the spot matures a reddish-brown, 
1 McAlpine, D., Fungus diseases of citrus trees in Australia and their 
treatment. Government Printer, Melbourne (1899) 21, 22, 81. 
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