2 BULLETIN 1286, U. S. DEPARTMENT OF AGRICULTURE 
that to-day in many districts there are left only occasional deserted 
plantings. 
Although the superior Para rubber (Hevea brasiliensis (Mull.) 
Arg.) was tried in a few plantings which survive even now in 
Mexico, Nicaragua, Panama, Colombia, Venezuela, and the TVest 
Indies, it was mainly in the Guianas and Brazil that this species was 
utilized ^ almost exclusively from the beginning. Here, unfortu- 
nately, in the general region which includes the native habitat of 
the tree the formerly very promising industry of the Guianas has 
been nearly ruined by the ravages of a destructive endemic leaf 
disease which spread from the scattered wild trees of the jungle 
to the thickly planted plantations. Although this disease, known 
generally as the South American leaf disease (Dothidella ulei 
P. Henn.), has received considerable attention from local botanists, it 
seemed desirable, in view of the increasing interest in rubber plant- 
ing in Central America and South America, to determine its present 
status, possibilities of control, and to what extent it may become a 
menace to renewed planting enterprises. For this purpose the writer 
was sent to Trinidad and the Guianas during the summer of 1923 to 
make a survey of the disease situation. The results, together with 
a general review of previous investigations, are incorporated in this 
bulletin. 
HISTORY AND GEOGRAPHIC DISTRIBUTION OF THE DISEASE 
The South American leaf disease was first reported in 1904 by 
P. Hennings (ii), 2 who published a short description of the causal 
fungus from diseased leaves collected from wild trees of Hevea 
brasiliensis in 1901 and 1902 by E. Ule in the upper region of the 
Amazon, near Jurua (Acre Territory), on the banks of the Kio 
Jurua Mirum (Acre Territory), and along the Amazon proper near 
Iquitos, Peru (fig. 1). Hennings named the perithecial form Dothi- 
della ulei and a pycnidial fungus, which appeared to be merely 
another stage on the same leaves, Aposphaeria ulei. The disease 
caused defoliation of the attacked leaves and was considered very 
injurious. Attention was called to the danger of its possible appear- 
ance in Hevea cultivations. 
The literature contains no further reference to this disease until 
1910, when A. W. Drost (6) briefly described a leaf trouble on 
nursery plants at Paramaribo, Dutch Guiana. Drost observed, in 
addition to pycnidia, a " Ramularia-like " conidial stage, but made 
no further effort toward its identification. His description of the 
symptoms, however, leaves little doubt that he was dealing with 
the disease in question. It was considered indigenous, having been 
found on the related Hevea guyanensis in its native habitat in the 
forests. In addition to the leaves, it was observed to attack young 
stems and twigs, causing warty swellings. The trouble was not 
considered serious. 
In 1911 Kuyper (13) published a more detailed description of 
the trouble in Dutch Guiana and mentioned its occurrence through- 
out the country both on plantations of Hevea brasiliensis and on 
2 Serial numbers (italic) in parentheses refer to "Literature cited," at the end of this 
bulletin. 
