LEAF DISEASE OF PAKA RUBBER 7 
Viewing the situation in Trinidad as a whole, although the leaf 
disease has doubtless been a discouraging factor in contemplated 
extension of rubber culture in certain parts of the island, in the 
eastern territory it has been of little consequence. 
BRITISH GUIANA 
In British Guiana most of the rubber has been planted on river 
lands at 100 to 200 feet elevation, and rarely does any occur more 
than 60 miles inland from the coast. Figures published annually 
in the Reports of the Department of Science and Agriculture show 
a steady decrease of acreage in production since 1917, when the 
South American leaf disease became generally prevalent. Owing 
to the ravages from this disease and the consequent abandonment of 
extensive areas, the export of rubber decreased from 20,384 pounds 
in 1920 to 1,568 pounds in 1921 (7, p. 11). The department's sta- 
tion at Christianburg had to be abandoned, as 95 per cent of the 
trees was seriously affected by the disease, which later became preva- 
lent at Issorora, the yield of dry rubber from tapped trees having 
fallen from 4.97 pounds in 1919 to 2.4 pounds in 1920. Trees which 
have been at all seriously affected by the disease never recover their 
original vigor. Although seriously injuring the foliage of the wild 
rubber trees (Hevea confusa), the disease did not appear to exert 
on them the intensely destructive action it did on Hevea hrasiliensis 
(9, p. 16). 
Eubber in British Guiana was planted largely in pure stands, 
which in many cases were surrounded by belts of jungle left to 
protect the trees from storms and winds. Such a situation furnished 
ideal conditions for the spread of the leaf disease to the plantings 
from its native habitat on the scattered wild rubber trees of the 
adjacent jungles. According to the present director of agriculture, 
Sir J. B. Harrison, the leaf disease has always been more severe in 
such protected plantings, whereas trees on exposed hills or higher 
land were generally less affected. Likewise, the rubber trees on 
low-lying coast areas exposed to sea breezes, where also owing to 
poor soil growth was slower, were noticeably less affected than the 
up-river estates. 
Some deserted plantings inspected by the writer on the lower 
Essequibo River showed strikingly the effects of the disease. One 
very dense planting about 12 years of age seemed to have suffered 
little until the last year or two, since the trunks were of normal size. 
At the time of examination, however, some of the trees showed 
numerous dead branches, and scarcely a half-grown leaf could be 
found which was not distorted or badly spotted, indicating a be- 
lated infection. Other trees with mostly mature leaves would have 
been considered as yet unattacked had there not been occasional dead 
branch tips indicating repeated defoliations last year. 
In a younger planting, 4 to 6 years of age, less than a quarter of 
a mile distant from the above, the disease was seen in its most 
active stage during an epidemic which had apparently been in 
progress for two weeks. Fully half the trees had just passed the 
" wintering " period and were developing new leaves, which aver- 
aged from a few days to a week or more in age. As pointed out by 
earlier writers, this period is less defined in the South American 
