Research into the Cultivation, Production Constraints and Farming Systems of Deepwater Rice in Bangladesh.

As Team Leader, I planned and coordinated studies on crop physiology and agronomy, on cropping systems and on pest and disease management (principally of stem borers and nematodes). Much of the research was conducted on farmers' land at sites representative of each of the three major floodplains. Various aspects of the crop agronomy - including planting practices, spacing, fertiliser use, herbicides and varietal selection (in collaboration with an IRRI outreach team) - were investigated by P. Francis, M.A. Rashid and N.M. Thompson. Farming systems research was initiated with T.C. Bene and H. Ali as the investigators. On my initiative, N.M. Thompson and T.C. Bene also began studies of the potential for ratooning deepwater rice and so achieving a more productive inter-cropping pattern. A collaborative programme on blue-green algae was led by B. Whitton of Durham University. My personal research, assisted by M.B. Alam, Q.M.A. Razzaque and Z. Islam, formed the principal pest management study, a summary of which is given below. Aspects of the ecology and population biology of Scirpophaga incertulas were studied by Z. Islam and formed the core of his doctoral thesis. Two nematologists, I. McGeachie and M.L. Rahman, concentrated on the important ufra disease, caused by the nematode Ditylenchus angustus, with good success in identifying mechanical methods for reducing the incidence and severity of the disease. M.L. Rahman also commenced studies of other disease-causing nematodes, Aphelenchoides besseyi and Meloidogyne graminicola, with his studies of the latter forming the core of his doctoral thesis. Investigations of rodent pests were undertaken in a collaborative study with BRRI mainstream staff, notably M.S. Ahmed.

In my own programme several methods were used to test claims that stem-borers, especially S. incertulas (YSB), cause serious crop loss in deepwater rice. Insecticides were used to assess whether control of different YSB broods would positively affect crop yield. In 1981, early season, pre-flood applications did reduce infestation but yield was not affected; the season's work, however, provided data which enabled construction of a borer population dynamics model. Other investigations in 1981 showed that infestation levels lower than 24% pre-flood and 42% at harvest did not affect yield. In 1982, strategic spraying studies were planned but YSB populations were very low in the early season. When light-traps showed an upsurge in adult moth numbers in mid- late-season,an insecticide, monocrotophos at 250g a.i./ha was applied from a boat. The experiments showed that one to three mid- to late-season applications significantly reduced infestation and/or the incidence of whiteheads (unfilled panicles), with yield savings (7-10%) similar to those which earlier workers had obtained by applying an insecticide (diazinon) 20 times in a season. Also in mid-season, anatomical studies of over 200 elongated stems revealed YSB larval feeding neither causes significant structural damage nor seriously interrupts nutrient flow, also passage of a larva through a nodal septum is not detrimental. Irrespective of YSB attack, the submerged lower internodes commonly die, the fibrous remains anchor the upper stem and nodal roots take over nutrient uptake. At harvest time, some 25,000 stems were collected from many project field trials, but 84 correlation calculations showed no consistent significant effects of infestation (27-60%, CV 40%) on yield. Detailed studies of panicle-bearing stems (n = 838) showed that, even with 97% stem infestation, most yield loss results from infestation of the terminal internode and is manifested predominantly as whiteheads. In a specific study, 94% whiteheads (n = 205) were associated with terminal internode infestation, where larval feeding in the narrow stem had disrupted food conduction, so preventing grain-filling.

My overall conclusion was that YSB is of significant importance primarily at the time of panicle initiation. Attack earlier in the season may lead to some loss of tillers, this is only one contributory factor to what is a totally normal decline of plant density from a peak around the time of flood onset (i.e. after the first of the monsoon rains) to what is a finite number of panicles per unit area. In essence, for much of the season YSB has the role of a near perfect parasite, causing no substantial damage to the host deepwater rice plant.

PUBLICATIONS

Personal -
Taylor, B. (1981) Deepwater Rice Pest Management Project - Phase 2 - 1981 to 1985. Planning document for the Government of Bangladesh and the UK Overseas Development Administration, 10 pp.
Taylor, B., Alam, M.B. & Razzaque, Q.M.A. (1982) Preliminary insecticide tests and observations for preflood control of yellow rice borer in deepwater rice. pp 475-487. In Proceedings of the 1981 International Deepwater Rice Workshop, IRRI, Manila, Philippines.
Taylor, B. (Ed.) (1983) Review of the ODA-BRRI Deepwater Rice Project, 1981-82. Background document for ODA/BRRI Review Mission, 52 pp; plus summaries, 8 pp; and annexes, 16 pp.
Rahman, M.L. & Taylor, B. (1983) Studies on nematode pests associated with deepwater rice in Bangladesh. International Rice Research Newsletter, 8, 20-21.
Taylor, B. (1984a) Deepwater rice and yellow stem borer larvae. International Rice Research Newsletter, 9, 21.
Taylor, B. & Islam, Z. (1984) Crop loss in deepwater rice caused by yellow stem borer. International Rice Research Newsletter, 9, 16-17.
Taylor, B. (1988a) The impact of yellow stem borer, Scirpophaga incertulas (Walker) (Lepidoptera: Pyralidae), on deepwater rice, with special reference to Bangladesh. Bulletin of Entomological Research, 78, 209-225.
Taylor, B. (1993) Flooding in Bangladesh. The Ecologist, 23, 36.
Taylor, B. (1996) Scirpophaga incertulas (Walker)(Lepidoptera: Pyralidae) and deepwater rice - an integrated view. Crop Protection, 15, 649-655.

Team -
Francis, P. & Griffin, G. (1982) Crop establishment practices for deepwater rice in Bangladesh. pp 415-424. In Proceedings of the 1981 International Deepwater Rice Workshop, IRRI, Manila, Philippines.
McGeachie, I. & Rahman, L. (1983) Ufra disease: a review and a new approach to control. Tropical Pest Management, 29, 325-332.
Ahmed, M.S., Alam, S. & Karim, A.N.M.R. (1984) Rat activity in the deepwater rice areas of Bangladesh. International Rice Research Newsletter, 9, ?.
Thompson, N.M. (1984) A comparative study on the growth and yield of transplanted deepwater rice and their ratoons in Bangladesh. MSc thesis, University of Reading, 71pp.
Rahman, M.L. (1987) Source of ufra-resistant deepwater rice. International Rice Research Newsletter, 12, 8.
Islam, Z. (1987) Studies on the ecology and management of yellow stem borer in Bangladesh deepwater rice. External PhD Thesis, University of London.
Rahman, M.L. (1987) Rice root-knot nematode, Meloidogyne graminicola, attacking deepwater rice in Bangladesh. External PhD Thesis, University of London.
Bene, T.C. (1988a) A potential cropping system based on ratooned deepwater rice in Bangladesh. pp 481-495. In Proceedings of the 1987 International Deepwater Rice Workshop, IRRI, Manila, Philippines.
Bene, T.C. (1988b) Ratooning ability of deepwater rice varieties and lines in Bangladesh. pp 497-511. In Proceedings of the 1987 International Deepwater Rice Workshop, IRRI, Manila, Philippines.
Islam, Z., Catling, H.D. & Pojananuwong, S. (1988) Attempts to control yellow stem borer in deepwater rice with insecticides. pp 551-558. In Proceedings of the 1987 International Deepwater Rice Workshop, IRRI, Manila, Philippines.
Karim, A.N.M.R., Ahmed,M.S., Mion, M.Y. & Haque, M.E. (1988) Rodent ecology and control in deepwater rice. pp 605-617. In Proceedings of the 1987 International Deepwater Rice Workshop, IRRI, Manila, Philippines.
Rashid, M.A., Jobber, M.A. & Siddique, S.B. (1988) Maximising productivity of deepwater riceland through ratooning and combining deepwater rice with high-yielding boro rice. pp 513-516. In Proceedings of the 1987 International Deepwater Rice Workshop, IRRI, Manila, Philippines.
Whitton, B.A., Aziz, A., Francis, P., Rother, J.A., Simon, J.W. & Tahmida, Z.N. (1988) Ecology of deepwater rice fields in Bangladesh. 1. physical and chemical environment. Hydrobiologia, 169, 3-22.
Islam. Z. (1990) Influence of Scirpophaga incertulas (Lepidoptera: Pyralidae) on deepwater rice. Bulletin of Entomological Research, 80, 301-308.
Rahman, M.L., Evans, A.A.F. & Miah, S.A. (1990) Plant damage and yield loss caused by the rice root-knot nematode, Meloidogyne graminicola, in deepwater rice. Bangladesh Journal of Botany, 19, 107-116.
Islam, Z. & Catling, H.D. (1991) Biology and behaviour of Scirpophaga incertulas (Walker) (Pyralidae: Lepidoptera) in deepwater rice. Journal of Plant Protection Tropical, 8, 91-102.
Islam, Z. (1992) Diapause in Scirpophaga incertulas (Pyralidae: Lepidoptera) in Bangladesh. Journal of Plant Protection Tropical. x, xx-xx.

INTERNATIONAL RECOGNITION
My view has gained support from a number of recent reports. For instance, Shephard and colleagues simulated YSB damage by cutting and removing tillers of a conventional high-yield rice (IR36). Detillering early in the season had little or no effect on resulting yields but yields were reduced significantly by detillering during panicle initiation and grain-fill stages¹. Similarly, Litsinger², reviewing crop loss assessment, has written - "the principal effect of early stem-borer attack is to kill tillers, but as these are produced in excess, considerable compensation by the crop is possible" and "there has been a tendency to equate crop injury with crop loss or to base crop loss assessments on untested assumptions, making no allowance for compensatory growth". The importance of the strategic spraying experiments has been acknowledged by Catling³, who described the best potential control strategy as that developed in Bangladesh - "with insecticides timed to control Brood 5 moths and applied with a motorised knapsack sprayer from a boat". He mis-attributed this work to Islam et al. (1988, see references in ³ ), a claim perpetuated by Catling & Islam⁴, with the additional incorrect note that the spraying was initiated by "a tentative threshold of 10% damaged stems at the booting to flowering stage". As can be seen in the above description of the work, Islam was my junior counterpart, Catling was not involved, and the action was determined by light-trap results.

Recently for Crop Protection, I refereed papers by E.G. Rubia and colleagues, from IRRI (Rubia, E.G. et al. 1996. Crop Protection, 15, 335-340) and by Islam and Karim, of BRRI (Islam, Z. & Karim, A.N.M.R. 1998. Crop Protection, 16, 303-311).

[¹ Shephard, B.M. 1990. Integrated pest management in rice: Present and future prospects in South-east Asia. In. Grayson, B.T., Green, M.B. & Copping, L.G., Eds. Pest Management in Rice. Elsevier, London, pp 258-268. ² Litsinger, J.A. 1991. Crop loss assessment in rice. In. Heinrichs, E.A. & Miller, T.A, Eds. Rice Insects: Management Strategies. Springer, New York, pp. 1-65. ³ Catling, H.D. 1992. Rice in Deepwater. Macmillan, London. ⁴Catling, H.D. & Islam, 1995. Crop Protection, 14, 57-67.]

Citations
Taylor & Islam 1984 - Catling, H.D. 1987. Crop Protection, 6, 20.
Taylor 1988a - Islam, Z. 1990. Bulletin of Entomological Research, 80, 301.

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©1998 - Brian Taylor CBiol FSBiol FRES 11, Grazingfield, Wilford, Nottingham, NG11 7FN, U.K.

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