Report on the padi-borer
L. Wray, Jr., Curator of the Perak Museum, published this entomological report in 1887 in response to a request from Dr. Leech, Collector and Magistrate of the Krian District, who had observed three successive seasons of escalating damage to padi crops from an unidentified maggot. The article provides the first systematic account of the rice-stem borer (Chilo species affinis C. oryzae of Riley) in the Malay Peninsula, documenting its complete life cycle, reproductive capacity, and the parasitic fly that serves as its principal natural check.
Summary
The report originated from a practical administrative problem: Dr. Leech’s letter of 1 January 1887 described acres of padi in Krian with complete stalks and ears but no grain, and requested identification and a remedy (p. 73). Wray undertook field observations in the Larut area and laboratory rearing experiments, producing a full morphological description of all four life stages—egg, larva, pupa, and imago—of what he identified as a Chilo species closely allied to Riley’s North American C. oryzae (pp. 74–75). He also described a second, less abundant borer moth species at the close of the article (p. 82).
The natural history section reveals the insect’s adaptive strategy across the cropping season. The first brood feeds on growing shoots and leaf midribs before hollow stalks form, while subsequent broods bore into the pith of the stalk itself, producing the characteristic “head-rot” or empty-ear damage that farmers observed (pp. 76–77). Wray estimated approximately six broods per year, each generation spanning roughly two months, with the cycle perpetuated between seasons through self-sown rice and lateral shoots of old plants left standing in the field under the Malay harvesting method (pp. 78, 80).
A significant portion of the report is devoted to the parasitic fly (family Muscidae, subfamily Tachinariae), which Wray identified as the most powerful natural check on the borer population. His field observations showed the parasite to be overwhelmingly dominant: in one examination he found five live parasitic pupae and three empty cases but not a single live borer pupa (p. 78). He concluded that without this parasitism, padi cultivation in the Malay manner would be “quite impossible” (p. 78). His recommended preventive measure—burning the straw promptly after harvest and suppressing self-sown rice between seasons—was already being circulated as a Malay-language notice by Dr. Leech (p. 74).
Key Findings
- A single female moth laid 11 egg masses in one night and 7 the next; one mass contained 39 eggs, yielding an estimated total of up to 600 eggs per female (p. 76).
- Approximately six broods mature per year, with each generation requiring about two months (p. 78).
- Up to 20 caterpillars were found in a single stool of young padi growing isolated in Taiping, more than two or three miles from any field, suggesting either long-range moth flight or an alternative wild host plant (p. 77).
- The parasitic fly larva withstood immersion in spirits for two and a half hours without dying, indicating remarkable hardiness (p. 79).
- The female borer moth lives approximately seven days in captivity, laying eggs on the second and third nights after emergence; males survive only three to four days (p. 77).
- The borer had been observed causing damage in Krian for three consecutive seasons by 1887, with each year worse than the last (p. 73).
Conclusion
Wray’s definitive takeaway is that the padi-borer, while destructive, is held in check by its parasitic fly to a degree that makes the crop viable, and that the principal human contribution to the problem is the Malay practice of leaving straw standing in the field between seasons, which provides continuous food for the borer’s inter-seasonal broods. He argues that a simple, coordinated act of burning the straw after harvest—combined with suppression of volunteer rice—would, with the parasite’s assistance, be sufficient to bring the pest under control (p. 81).
Context
- Wray held the colonial appointment of Curator, Perak Museum, and the report was produced at the request of a British administrative officer (the Assistant Resident of Perak), reflecting the pattern of colonial scientific institutions responding to practical agricultural concerns raised by district officers.
- The article draws on Wray’s own field collections and rearing experiments in the Larut and Taiping areas of Perak; no external archival collections are cited.