Scent of the New Zealand honeydew beech forest and the attraction of introduced Vespula wasps

Robert Brown *1, Ashraf El-Sayed 2, Jacqueline Beggs 1, Max Suckling 2

1 School of Biological Sciences, University of Auckland, 261 Morrin Rd Tamaki Campus, Aucland 1142, NZ
2 The New Zealand Institute for Plant & Food Research Limited, Private Bag 4704, Christchurch 8142, NZ

The introduction of social Vespula wasps to New Zealand has been disasterous for many of the native ecosystems. This is particularly true in the black beech forests (Nothofagus spp.) of the South Island, where these wasps are able to reach very high population densities due to the abundance of honeydew produced by native scale insects (Ultracoelostoma spp.) that feed on the phloem of black beech trees.  There is a very characteristic aroma associated with honeydew in beech forests that we hypothesized is attractive to wasps.  Volatile collections were taken of trees with honeydew present on the trunk in the field using portable solid phase microextraction (SPME), and analysed with a gas chromatograph-mass spectrometer.  Five aromatic compounds were found in the headspace and were shown to elicit an antennal response from workers of both V. vulgaris and V. germanica using an electroantennagram.  Field trapping tests using these five compounds both individually, and in blends, provided conclusive evidence of wasp attraction to only a portion of the treatments tested.

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