Pine volatiles mediate host selection for oviposition by Thaumetopoea pityocampa (Lep., Notodontidae) M. R. Paiva 1 , E. Mateus 1,2 , M. H. Santos 3 & M.R. Branco 3 1 CEF, Dep. Cie ˆ ncias e Engenharia do Ambiente (DCEA),Faculdade de Cie ˆ ncias e Tecnologia, FCT, Universidade Nova de Lisboa, Caparica, Portugal 2 CENSE, Dep. Cie ˆ ncias e Engenharia do Ambiente (DCEA), Faculdade de Cie ˆ ncias e Tecnologia, FCT, Universidade Nova de Lisboa, Caparica, Portugal 3 Centro de Estudos Florestais (CEF), Instituto Superior de Agronomia (ISA), Technical University of Lisbon (UTL), Lisbon, C, Portugal Introduction The pine processionary moth, Thaumetopoea pityocampa Denn. & Schiff. (Lep., Notodontidae), hereafter PPM, is the most important pine defoliator in the Mediterra- nean region, causing severe damage to conifers and even total stand defoliation (e.g. Ho ´ dar et al. 2003). Additionally to pine defoliation and consequent growth reduction, T. pityocampa larval urticating hairs give rise to public health problems (e.g. Lamy et al. 1986; Vega et al. 2000), originating economic losses (Gatto et al. 2009), mainly in urban and recreational green areas. Over the past decades, PPM geographical range of distribution has been expanding, both northwards and in altitude, mainly in the Alps, probably due to climate warming (e.g. Benigni and Battisti 1999; Goussard et al. 1999; Battisti et al. 2005). Thaumetopoea pityocampa phenology is influenced by local climatic conditions. In Portugal, larval devel- opment and the resulting pine defoliation unfold throughout the winter and pupation takes place by Keywords Pinus spp., egg laying, olfactory cues, pine processionary moth, sesquiterpenes, terpenes Correspondence M. R. Paiva (corresponding author), DCEA, Faculdade de Cie ˆ ncias e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal. E-mail: mrp@fct.unl.pt Received: May 11, 2009; accepted: April 24, 2010. doi: 10.1111/j.1439-0418.2010.01550.x Abstract The oviposition behaviour and host selection by females of the pine pro- cessionary moth, Thaumetopoea pityocampa, was studied under two condi- tions: in a field insectary and in a pine stand. An oviposition choice test was conducted in an insectary cage, using artificial Christmas trees (ACTs) baited with extracts from four pine species: Pinus pinea, Pinus pin- aster, Pinus halepensis and Pinus brutia, plus a control. Females oviposited significantly more egg batches on the ACT baited with a P. brutia extract, while no oviposition occurred on the control ACT. In a large P. pinea stand, two groups of randomly selected trees were marked and baited respectively with an extract of P. brutia, which was the preferred species under insectary conditions and with a solvent, to act as control. Results showed that oviposition in the field followed an aggregated pat- tern, fitting a negative binomial distribution and that trees baited with P. brutia extracts, received a significantly larger number of egg-batches than control trees. In parallel, the volatiles emitted by all pine extracts tested where analysed by gas chromatography and mass spectrometry (GC-MS), coupled to a time-of-flight (TOF) mass analyser after solid phase microextraction (SPME), resulting in the identification of 26 com- pounds. Comparative chromatograms showed qualitative differences among the pine species used, some compounds being present in one of them only. Findings demonstrate for the first time that: (i) T. pityocampa females discriminate among bouquets extracted from different host pine species and exhibit oviposition preferences; and (ii) olfactory cues play an important role in mediating the selection process. J. Appl. Entomol. J. Appl. Entomol. 135 (2011) 195–203 ª 2010 Blackwell Verlag, GmbH 195