Abstract:
The cossid moth (Coryphodema tristis) has a broad range of native tree hosts in South Africa.
The moth recently moved into non-native Eucalyptus plantations in South Africa, on
which it now causes significant damage. Here we investigate the chemicals involved in
pheromone communication between the sexes of this moth in order to better understand its
ecology, and with a view to potentially develop management tools for it. In particular, we
characterize female gland extracts and headspace samples through coupled gas chromatography
electro-antennographic detection (GC-EAD) and two dimensional gas chromatography
mass spectrometry (GCxGC-MS). Tentative identities of the potential pheromone
compounds were confirmed by comparing both retention time and mass spectra with authentic
standards. Two electrophysiologically active pheromone compounds, tetradecyl acetate
(14:OAc) and Z9-tetradecenyl acetate (Z9-14:OAc) were identified from pheromone
gland extracts, and an additional compound (Z9-14:OH) from headspace samples. We further
determined dose response curves for the identified compounds and six other structurally
similar compounds that are common to the order Cossidae. Male antennae showed
superior sensitivity toward Z9-14:OAc, Z7-tetradecenyl acetate (Z7-14:OAc), E9-tetradecenyl
acetate (E9-14:OAc), Z9-tetradecenol (Z9-14:OH) and Z9-tetradecenal (Z9-14:Ald)
when compared to female antennae. While we could show electrophysiological responses
to single pheromone compounds, behavioral attraction of males was dependent on the synergistic
effect of at least two of these compounds. Signal specificity is shown to be gained
through pheromone blends. A field trial showed that a significant number of males were
caught only in traps baited with a combination of Z9-14:OAc (circa 95% of the ratio) and Z9-
14:OH. Addition of 14:OAc to this mixture also improved the number of males caught, although
not significantly. This study represents a major step towards developing a useful attractant to be used in management tools for C. tristis and contributes to the understanding
of chemical communication and biology of this group of insects.
