Submitted to: Entomological Experimental Applied
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/1/2007
Publication Date: 6/1/2007
Citation: Siderhurst, M.S., Jang, E.B. 2007. N-butyl (e)-7,9-decadienoate: sex pheromone component of the nettle moth, darna pallivitta. Entomologia Experimentalis et Applicata. 125(1):63-69. Interpretive Summary: Infestations of the nettle caterpillar were first discovered at a nursery in Panaewa, on the eastern side of the island of Hawai’i. D. pallivitta caterpillars have a wide host range, feeding on many agricultural crops, including coffee and macadamia, as well as landscape plants thereby threatening a nursery industry valued at $97.7 million. Transportation of contaminated nursery stock is a potential source of outbreaks in unaffected areas of Hawai'i, other Hawaiian islands and the U.S. mainland. D. pallivitta is a problem for farmers as a direct pest and secondarily as a quarantine pest, causing additional losses when shipments of infested plants are rejected by quarantine inspectors. Already inspectors have intercepted caterpillars and cocoons in California. Additionally, the caterpillar constitutes a human health hazard due to the painful sting, which results from contact with its urticating hairs (for which it is named). Current detection of the nettle caterpillar, D. pallivitta, relies on light trapping and visual surveys, techniques that are less specific, slower and more time consuming than pheromone trapping. The nettle moth pheromone identified herein will allow rapid detection of this irritant-causing/economically-important invasive pest, and also may provide the basis for control options such as pheromone mating disruption.
Technical Abstract: The nettle caterpillar, Darna pallivitta (Moore), is an invasive pest on the island of Hawai’i, causing defoliation of ornamental nursery stock and posing a human health hazard due to their urticating hairs that can cause painful stings. Wind tunnel and field tests with 2 day old moths revealed male behavioral responses to caged females consistent with a female released sex pheromone. Coupled gas chromatography-electroantennogram detection (GC-EAD) analysis of abdominal tip extracts revealed two male electroantennographically active compounds produced by female D. pallivitta. Mass spectral analysis and subsequent synthesis identified the active compounds as n-butyl (E)-7,9-decadienoate (major component) and ethyl (E)-7,9-decadienoate (minor component), both structurally similar to sex pheromone components previous reported from related Darna spp. Additionally, methyl (E)-7,9-decadienoate was identified from female abdominal extracts and a strong EAD response was elicited by the synthetic compound. n-Butyl (E)-7,9-decadienoate was the only component detected by solid phase microextraction (SPME) collections from single calling female moths, however the apparent absence of minor components may be a result of their lower abundance. Field trials showed significant attraction to all lures containing the n-butyl ester, while the methyl and ethyl esters did not increase trap captures at the levels and ratios tested. Synthetic pheromone lures (2.5 mg) outperformed virgin moths as attractant baits and could be used for monitoring D. pallivitta populations of the island of Hawai'i and detection on other Hawaiian islands and at ports and nurseries that receive plants from Hawai’i (e.g. California and Florida).