UNITED STATES DEPARTMENT OF AGRICULTURE 
DEPARTMENT BULLETIN No. 1380 
Washington, D. C. 
Issued May, 1926 
A PATHOLOGICAL SURVEY OF THE PARA RUBBER TREE (HEVEA 
BRASILIENSIS) IN THE AMAZON VALLEY 
By James R. Weir, Pathologist of the Expedition of the United States Depart- 
ments of Agriculture and Commerce to Investigate the Sources of Crude 
Rubber in the Amazon Valley and Pathologist in Charge of Pathological 
Collections, Bureau of Plant Industry 
CONTENTS 
Page 
Preface 1 
General pathological conditions and 
sanitation 2 
Diseases of Hevea 3 
Host relationships 3 
Regional peculiarities 4 
Intercrops 4 
Destruction of jungle debris 5 
Special diseases 6 
Root diseases 6 
Stem and branch diseases 19 
Leaf diseases 33 
Fruit and flower diseases 51 
Injuries caused by phanerogamic 
plants 53 
Physiological disturbances and ab- 
normalities 56 
Brown bast 56 
Pago 
Physiological disturbances and ab- 
normalities — Continued. 
Wounds 58 
Preventitious and adventitious 
nodule structures 68 
Cortex nodules 70 
Abnormal exudations of latex 72 
Rubber pads 73 
Chlorosis of leaves 74 
Abnormal growths and condi- 
tions 74 
Soil and moisture relations 76 
Prepared rubber 77 
Fungi reported on Hevea 79 
Mistletoes on Hevea 94 
Algae on Hevea 96 
Bibliography 97 
PREFACE 
During the period from August 3 to November 26, 1923, the writer, 
as pathologist of the expedition of the United States Departments of 
Agriculture and Commerce to investigate the sources of crude rubber 
in the Amazon Valley, studied the diseases of Hevea brasUiensis 
and related species. These investigations have resulted in a wide 
acquaintance with plant diseases in this interesting forest region, 
and an extensive collection of forest fungi 1 bearing on the pathology 
of Hevea has been made. Man} T of the fungi found are very imper- 
1 Recognizing the value of illustrations in work of this nature, many reproductions of 
photographs are used. Those from the field were photographed by M. K. Jessup. The 
detail photographs are the work of Robert L. Taylor, of the Bureau of Plant Industry. 
Plates XV to XVIII are by J. M. Shull, of the same bureau. 
For many helpful suggestions and assistance in determining doubtful specimens of 
fungi the writer wishes to acknowledge his indebtedness to C. L. Shear, YY. W. Diehl, 
Miss V. K., Charles, and Miss A. E. Jenkins, of the Office of Pathological Collections of 
the Bureau of Plant Industry, and also to C. C. Plitt, of Baltimore, Md.. for determining 
some of the lichens. Thanks are also due to Miss Sara Young aud Miss K. K. Cash for 
assistance in bibliographic work. 
61384°— 26 1 1 
