Factors affecting catch of the black-headed caterpillar, Opisina arenosella Walker in sex pheromone-baited traps and evidence for population suppression by mass trapping

Abstract

The black-headed caterpillar, Opisina arenosella Walker (Lepidoptera: Oecophoridae) is a major and most destructive pest of coconut palm. Feeding habit and spatially segregated distribution with a discrete flight period of 32.44 ± 4.45 (Mean ± SD) days per generation make it difficult to employ insecticide sprays. In this study, we explored the utility of sex pheromone by exploiting its distribution and flight behaviour. The pheromone trap colour, its suspended height, density and design were evaluated. White cross-vane traps suspended in the middle of the palm canopy at a density of 40–120 traps ha−1 proved to be the most effective among tested. White cross-vane traps baited with synthetic pheromone, (Z,Z,Z)-3,6,9-Tricosatriene for three consecutive moth emergence periods and trapped 1,34,084, 9012 and 4126 moths in Nittur, Nelamangala and Bidadi, respectively. Further, there was a reduction in larvae per leaflet from 2.28, 1.17 and 0.83, to 0.11, 0.12 and 0.06, in the three respective sites. There was subtle to no change in the larval abundance in the control plots across the generations. Our results suggest suitable mass trapping technique may substantially suppress the O. arenosella population on coconut.