Unless definitively stated, results based on using the rapid, quantitative method of stem dissection indicate infestation by stem-borers without denoting the species involved. Intensive surveys, such as Catling & Islam (1979), confirmed by work reported below, however, have shown that it is only at the beginning and the end of the season, when the fields are not flooded, that species other than S. incertulas are present in observable numbers. Thus, in the text and tables, the use of the term stem-borers can be taken as primarily indicating S. incertulas infestation. Panicle weights, for use in calculating yield data, were determined by weighing all filled, healthy grains and standardizing for a 14% moisture content.