A disease of the angsanatree
C.X. Furtado, a botanist at the Singapore Botanic Gardens, published this article in 1935 to document his field observations on a devastating disease affecting Pterocarpus indicus (Angsana) trees across the Malay Peninsula. The article’s central thesis is that the disease is not caused by a root fungus or senile decay, as previously theorised by Fox, Bancroft, and Chipp, but by the sustained parasitic action of a jassid (leafhopper) insect that disrupts the tree’s physiology through feeding on tender shoots and leaves.
Summary
The article reviews the history of the Angsana disease from its first recorded appearance in Malacca approximately sixty years prior to publication, through its progressive spread to Penang, the Federated Malay States, and Singapore. Furtado synthesises the observations of previous workers—Fox, Derry, Gallagher, Bancroft, Burkill, and Chipp—who had variously attributed the disease to root fungi (particularly Polyporus species), senile decay from repeated vegetative propagation by cuttings, or unspecified fungal agents. He then presents his own intensive field observations made from April 1923 onwards, primarily in the Nassim Road Avenue near Tanglin Barracks and at St. John’s Island, Singapore.
Furtado’s key contribution is a systematic elimination of competing hypotheses. He demonstrates that the characteristic symptom—a continuous longitudinal strip of dead cortical tissue extending from a root up the stem and into the branches—cannot be explained by any of the previously proposed fungal agents, none of which was found in constant association with the disease or in living tissue. His failed inoculation experiments, repeated over two years, further undermine the fungal hypothesis. He then identifies a jassid insect as invariably present in all diseased avenues and absent from healthy ones, arguing that its sustained feeding on tender growth causes profound physiological disturbances—reduced assimilation, disrupted translocation of photosynthetic products, and possibly destruction of root-regenerating hormones—that ultimately kill the tree. The article also addresses practical questions of control, concluding that spraying is impractical given the insect’s capacity for long-distance aerial dispersal and the tropical climate’s frequent rainfall.
Key Findings
- The disease was first recorded in Malacca approximately 60 years before 1935 (c. 1875), destroying an entire sea-front avenue; it appeared in Penang in 1906, in Tapah in December 1910, simultaneously in Taiping, Kuala Kubu, and Kuala Lumpur in 1912, in Pulau Brani in 1914, and in Singapore’s Connaught Drive in 1917 (pp. 163–164).
- Furtado’s inoculation experiments, repeated three times over two years on healthy trees and twice on young cuttings, all yielded negative results, ruling out direct fungal or bacterial transmission through soil or root contact (p. 176).
- The jassid was found in all diseased avenues in Singapore, Penang, Kedah, Taiping, Kuala Lumpur, and Malacca during visits between 1925 and 1928, and was absent from avenues free of disease (pp. 177–178).
- Coppice shoots from stumps of trees killed by the disease grew healthily for over ten years without showing symptoms, and cuttings taken from dying branches struck roots and remained healthy after the parent trees had died (p. 175).
- The oldest Angsana trees that died in Singapore’s Connaught Drive avenue were only 28 years old (planted 1890, died 1918), undermining the senile decay theory (p. 179).
- Two specimens of Pterocarpus macrocarpus in the Economic Garden, Singapore, remained free from jassid attack while a nearby Angsana tree was heavily infested, suggesting potential immunity in allied species (p. 189).
Conclusion
Furtado concludes that the Angsana disease is an aerial infection caused by a jassid insect whose sustained parasitic feeding on tender shoots and leaves produces profound physiological disturbances—reduced photosynthetic capacity, disrupted translocation of assimilates, and probable destruction of root-regenerating hormones—that ultimately kill the tree. The disease’s characteristic march from sea-fronts inland and its epidemic pattern in avenues are consistent with wind-dispersed insect vectors rather than soil-borne pathogens. He recommends restricting Angsana planting to short, widely separated avenues mixed with other species as the only practicable control measure.
Context
- The article draws on Furtado’s own field observations (1923–1934) at the Singapore Botanic Gardens, Nassim Road Avenue, and St. John’s Island, supplemented by unpublished correspondence with A. Sharples (mycologist, Agricultural Department, S.S. & F.M.S.) and Dr. N.G. Cooper (Quarantine Station, St. John’s Island).
- Historiographically, the article represents a significant shift in the understanding of the Angsana disease from a fungal to an entomological aetiology, though Furtado himself acknowledges the circumstantial nature of his evidence and the absence of a definitive transmission experiment using the jassid alone.