Surveys on the stem borer complex of rice were initiated at Mbita Point Field Station during 1980–1981. Stem borers collected and identified so far included Maliarpha separatella Rag; Diopsis thoracica West; Sesamia calamistis Hmps., and Chilo partellus Wlk. Among these four species, M. separatella was the most abundant and showed highest infestation during the reproductive and ripening phases of the rice crop. D. thoracica was found to cause greatest damage on the crop during the crop's tillering phase. It is suggested that there may be differences in Maliarpha infestation due to rice varieties.
