Introduction

Deepwater rice, Oryza sativa, is grown in a vast area (over 5.5 million ha) of South and South-East Asia, where seasonal flooding of 1-3 m depth occurs, and is the staple food for many millions of people. It has the remarkable characteristic of being able to respond to rising flood waters by rapid stem elongation. During the past two decades or so, there has been considerable research into the cultivation of this unique crop and the constraints which affect its yield.

One of the major production constraints is the feeding activity of larvae of the yellow stem borer Scirpophaga incertulas (Walker) (Lepidoptera: Pyralidae). There is controversy, however, about how serious an impact this pest has upon the crop and when during the growing season (approximately March to November) that impact is greatest. On one hand is an apparently firm belief that S. incertulas is the key pest with severe impact throughout the crop life cycle (Catling & Islam, 1995, et ante.). I, on the other hand, after specifically designed studies and a review of all available evidence from entomological and agronomic research in Bangladesh and Thailand, felt compelled to propose an alternative, integrated conclusion.

In essence, that is while S. incertulas can contribute to the annual decline in tiller numbers, from a peak around the time of onset of flooding, the decline takes place even in seasons when the pest is effectively absent, and is a wholly normal event emanating from primarily agronomic factors. Late season infestation, when larval feeding affects the terminal, panicle-bearing internode, however, can lead to major crop loss.

This is a view which I felt was sensible by the end of my first season in Bangladesh (1981) and outlined to the 1981 Deepwater Rice Conference in Bangkok (Taylor, Alam & Razzaque, 1982). The experiments in 1982 reinforced the interpretation and summary articles were submitted to the IRRI Newsletter (as it then was) in 1983, and appeared in print in 1984 (Taylor, 1984, Taylor & Islam, 1984). When published, however, both articles had been altered by the editors and the interpretation of the findings was no longer as had been submitted. Indeed, as the illustrations (click here) show not only was information removed but comments totally contrary to the evidence were added!

I had moved on to other things by the time of publication so felt there was little point in reacting. What I did was to prepare the fuller account published as Taylor (1988). That, I felt, presented the evidence from both angles and gave a balanced analysis of a biologically interesting argument. Although, uncredited, my conclusions seem to have had an impact on thinking concerning YSB, such as in the review by Litsinger (1991). That review dealt mainly with conventional paddy rice and did not have much on either deepwater rice or yellow stem borer, but it is significant that Litsinger remarked '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, also, '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'.

It was much to my surprise, therefore, when I obtained a copy of David Catling's 1992 opus on "Deepwater Rice". In what is a very comprehensive literature listing, up to and including papers as late as 1991, there is no mention whatever of my publications!

What I did find, however, were clear changes in Catling's thinking over the "damage" caused by S. incertulas. This could be read in statements made without any source of evidence. I also found recognition that the best results in Bangladesh were obtained with insecticides timed to control Brood 5 moths and applied with a motorized knapsack sprayer from a boat. That, however, was credited to Islam, Catling & Pojananuwong (1988). This misattribution was compounded by the subsequent publication of a statement that use was made of 'a tentative action threshold of 10% damaged stems at the booting to flowering stage' (Catling & Islam, 1995).

The publication of the latter paper stimulated me to submit a riposte to the same journal (Crop Protection). This was published (Taylor, 1996) but the niceties of formal journals restrained my notes. That, and the opportunity to use a much greater range of visual evidence, provided the incentive for this section of the website.

The first phase - 1978-80

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