640 The Philippine Journal of Science 1920 
darin oranges have given positive results in Manila; we have 
no data as yet for other species of Citrus. 
CONTROL 
There are no experimental data regarding control of this 
disease in an affected orchard. The writer’s inoculations have 
shown that fruits are only susceptible when approaching matur- 
ity, while immature fruits give negative results when inoculated. 
It is possible, therefore, that an easy orchard control, by spray- 
ing, could be developed. 
For countries where the disease is not yet present, however, 
as in California, the Gulf States of America, and Japan, the best 
control is of course entire prevention by excluding the disease.” 
The best of control methods by spraying are not 100 per cent 
efficient and in addition cause an annual outlay which is repeated 
year after year. Exclusion of the fungus by the plant-quaran- 
tine officers would be 100 per cent control and would cost but a 
small amount as compared with the yearly outlay for spraying. 
The situation in the Philippines with regard to this disease is 
peculiar. Black-spot disease, as has been said, has not been » 
observed here as yet upon Philippine-grown oranges. Oranges 
imported from China and found everywhere on the markets are 
sometimes severely affected with the disease, affording a source 
of infection of Philippine citrus fruits just at the period when 
such fruits are ripening. The absence of the disease in the Phil- 
ippines is therefore probably due to climatic conditions or pos- 
sibly to the phenomenon that ordinarily the rind of Philippine 
citrus fruits does not mature and turn yellow, but remains green 
up to picking time. Since citrus fruits are only susceptible 
when the rind is well matured, the absence of the disease may 
be due to the absence of susceptible tissue. This point may be 
cleared up in future experiments. 
SUMMARY 
1. Black spot, a disease described by McAlpine from Australia 
in 1899, has also been observed throughout southern China. It 
is not yet in Japan or America or in the orchards in the Phil- 
ippines. The disease consists of a black blemish on the fruits; 
it is not found on the leaves or branches. 
2. The fungus Phoma citricarpa McAlpine was isolated from 
black-spot lesions and, on inoculation upon healthy orange fruits, 
reproduced the disease. Control punctures remained negative. 
