Coconut is one of the major crops of commercial importance among the palms. The leaf-eating caterpillar Opisina arenosella Walker is the most important lepidopteran pest of coconut palm in India and Sri Lanka. Assessment of crop loss is essential for a realistic planning for research and developmental policies. Information on the yield loss in coconut due to O. arenosella attack is very meagre. In the present study, results of investigations carried out on leaf-eating caterpillar-induced yield loss in coconut palms in Kerala, India, for a period of 4 years (2002–2005) are presented. A maximum crop loss of 45.4% in terms of nut yield was recorded from infested palms in the succeeding year of severe pest incidence. The infested palms also showed reduction in bunch and leaf production to the tune of 21.0 and 13.8%, respectively. The pest-attacked palms regained their normal yield potential by the fourth year after heavy pest infestation.

Plumbagin, a napthoquinone from the plant Plumbago zeylanica, delayed pupation when topically applied to newly moulted final instars of the leaf eating caterpillar Opisina arenosella Walker (Lepidoptera: Oecophoridae). Pupae from treated larvae emerged into non-viable adults and had abnormalities such as deformed wings and shrunken abdomens; they also died much before the control insects. The results suggest that plumbagin interferes with the process of development and ecdysis of the insect.

The ovisite preference of Goniozus nephantidis (Hymenoptera: Bethylidae) was studied in relation to its hosts, Opisina arenosella, the coconut pest and Corcyra cephalonica, the flour pest. In both hosts, eggs were laid on all the segments except the first thoracic and the last four abdominal segments. Among the abdominal segments, the most preferred were segments 2 and 3 in the case of O. arenosella and 4 and 5 in the case of C. cephalonica. The percentages of eggs located intrasegmentally were 91.35 and 86.19; those of eggs located intersegmentally were 8.65 and 13.80 in the case of O. arenosella and C. cephalonica respectively. The left side was preferred in each host. In most of the egg clutches on O. arenosella, the head end faced the caudal end of the host; on Corcyra cephalonica, the head end faced the head end of the host.