Host attractants for the banana stem borer, odoiporus longicollis (coleoptera: curculionidae): Identification, electrophysiological activity and behavioural bioassay

Abstract

Steam volatiles of freshly cut banana stem were analyzed by combined gas chromatography-electroantennographic detection (GC-EAD) and combined gas chromatography-mass spectrometry (GC-MS) to identify n-hexanol, n-hexanal, n-pentanol and cis-3-hexenol as host attractants for the banana stem borer, Odoiporus longicollis. Identities of the above compounds were confirmed by comparative studies with authentics. Female weevils responded slightly more (EAG 1.41± 0.01) than male weevils (EAG 1.04 ± 0.03) to the steam distillate. Synthetic equivalents of the above attractants were subjected to EAG assay and n-hexanol elicited the highest EAG response (0.39 ± 0.02 mV) in the antenna of this weevil. The other synthetic attractants, n-hexanal, n-pentanol and cis-3-hexenol elicited EAG responses in the following order; 0.15 mV, 0.10 mV, 0.09 mV. A mixture of the above synthetic attractants (SAM) also elicited a poor EAG response (0.2 mV) in O. longicollis. In field experiments n-hexanol singly or in combination with the aggregation pheromone of O. longicollis failed to attract any weevils into traps. The synthetic attractant mixture (SAM) also was not field attractive while its combination with the aggregation pheromone of O. longicollis was attractive with a maximum mean catch of 0.66 ± 0.21 weevils/trap/week. Under the same conditions, however, the pest's known attractant system, the aggregation pheromone + banana stem tissue baited trap, had a maximum mean catch of 29.16 ± 7.02 weevils/trap/week.