Identification and field evaluation of female sex pheromone of leaf-eating caterpillar, Opisina arenosella (Lepidoptera: Oecophoridae)

The leaf-eating caterpillar, Opisina arenosella Walker, is the most destructive pest of coconut palm in India and Southeast Asia. The management practices employed against O. arenosella so far have been unsuccessful in many instances in India, due to the pest behaviour and coconut palm phenology. The life cycle, incidence and behaviour of O. arenosella are rather interesting and useful for the intervention of pheromone trapping technique for its management. We conducted the present study with the intention of identifying the female sex pheromone of O. arenosella and testing its efficacy under field conditions. Gas chromatography coupled electroantennographic detection (GC-EAD) and gas chromatography-mass spectrometry (GC-MS) analysis of female pheromone glands extract of one-day-old O. arenosella females confirmed the presence of (Z,Z,Z)-3,6,9-tricosatriene (Z3Z6Z9-23Hy) as the dominant sex pheromone component. The male antennal response to female pheromone gland extract and synthetic Z3Z6Z9-23Hy was recorded using GC-EAD, and the results revealed that antennal response was positive to both the treatments at 0.13 mV and 0.14 mV respectively, compared to control (air), which was 0.016 mV. It was also evident from wind-tunnel experiments that the male moth response was high (80%) with the female gland extract, compared to 60% with synthetic pheromone and 0% for control (air). Male moths caught in the traps with and without lure were assessed in two field sites and recorded 69.26% and 54.25% more moth catches in the traps with the lure. We also observed a similar result in the cage experiment in which male moths caught in the traps with and without lure were 64.50% and 12.40%, respectively. The study also confirmed that 93.20% moths caught in the pheromone-baited traps were male. From the study, it is evident that the presence of (Z,Z,Z)-3,6,9-tricosatriene, which is the sex pheromone compound from the female gland extract of O. arenosella, is an effective attractant in pheromone traps for the male moth under field conditions.