Identification, synthesis and activity of sex pheromone gland components of the autumn gum moth (Lepidoptera: Geometridae), a defoliator of Eucalyptus

Abstract

The autumn gum moth, Mnesampela privata (Guenée) (Lepidoptera: Geometridae), is native to Australia and can be a pest of plantation eucalypts. Field-collected and laboratory-reared female autumn gum moths were dissected to remove glands likely to contain components of the sex pheromone. Using gas chromatography (GC) and combined gas chromatography-mass spectrometry (GC-MS), three compounds were identified from female extracts, namely (3Z,6Z,9Z)-3,6,9-nonadecatriene, 1-hexadecanol and 1-octadecanol (confirmed by comparison with synthetic samples). Nonadecatriene elicited an antennal response in male autumn gum moth during gas chromatographic analyses combined with electroantennographic detection (GC-EAD). In electroantennogram (EAG) recording male M. privata antennae responded to the nonadecatriene. Nonadecatriene was synthesised via Kolbe electrolysis, starting with (9Z,12Z,15Z)-octadeca-9,12,15-trienoic acid (linolenic acid) and propanoic acid or via an alternative four-step method also starting from linolenic acid. In field trials (3Z,6Z,9Z)-3,6,9-nonadecatriene proved attractive to male moths. Thus, we conclude that (3Z,6Z,9Z)-3,6,9-nonadecatriene is a sex pheromone component of autumn gum moth. This component has been identified in extracts from other geometrids in the same subfamily, Ennominae. However, to our knowledge this is the first example where (3Z,6Z,9Z)-3,6,9-nonadecatriene has been found in females and also proved attractive to male moths when presented on its own. Our results are discussed in relation to other geometrid pheromones.

Identification, Synthesis and Field Testing of (3Z,6Z,9Z)-3,6,9-Henicosatriene, a Second Bioactive Component of the Sex Pheromone of the Autumn Gum Moth, Mnesampela privata

“…Identities of major compounds were assigned based on the previous report from Steinbauer et al (2004) on this species, mass spectra, and Kovats retention indices relative to those reported in the NIST Chemistry WebBook (http:// webbook.nist.gov/chemistry/). Lower levels of trienes were detected in moth extracts by selected ion monitoring (SIM) using characteristic ions at m/z 79 and 108, which were used for comparison of C19 and C21 triene levels.…”

“…Therefore, it is likely that additional pheromone components are used by M. privata. Steinbauer et al (2004) detected two alcohols (1-hexadecanol and 1-octadecanol) in some female M. privata extracts, but neither compound elicited significant antennal responses in males, nor did their addition to lures containing C19 triene enhance trap captures.…”

“…Östrand et al (2007) used traps baited with 1 mg of C19 triene to monitor populations of male M. privata in Tasmania and Victoria, and found trap catches were significantly correlated with subsequent oviposition. However, Steinbauer et al (2004) speculated that M. privata may use other compounds in its sex pheromone, as field catches were low at a site with an outbreak population. Furthermore, in our trapping trials in Eucalyptus plantations in Tasmania, South Australia, Victoria, and Western Australia during 2005 and 2006, using pheromone traps baited with 1 mg of C19 triene, captures of male M. privata were negligible despite the known presence of moths, eggs or larvae (P. Walker unpublished data).…”

“…The use of two or more components in a pheromone is often crucial in maintaining a discrete, species-specific chemical communication channel (Cardé and Baker 1984;Millar et al 1990). Although M. privata is the only Australian geometrid in which C19 triene has been verified as a sex pheromone component, Steinbauer et al (2004) gave indirect evidence that this compound is used for communication by other sympatric species as three species of Ennominae (two belonging to the same genus) also were caught during field trials. Therefore, it is likely that additional pheromone components are used by M. privata.…”

“…A synthetic pheromone lure for monitoring males of this species was developed after identification of the polyene hydrocarbon (3Z,6Z,9Z)-3,6,9-nonadecatriene (C19 triene) as a bioactive component in female abdominal tip extracts (Steinbauer et al 2004). Östrand et al (2007) used traps baited with 1 mg of C19 triene to monitor populations of male M. privata in Tasmania and Victoria, and found trap catches were significantly correlated with subsequent oviposition.…”