Agricultural and Forest Entomology (2013), 15, 65–76 DOI: 10.1111/j.1461-9563.2012.00588.x Biology and monitoring of Dryocosmus kuriphilus on Castanea sativa in Southern Italy Umberto Bernardo * , Luigi Iodice * , Raffaele Sasso *† , Valerio A. Tutore ‡§ , Pasquale Cascone * and Emilio Guerrieri * * Istituto per la Protezione delle Piante, Consiglio Nazionale delle Ricerche, Via Universit` a 133, 80055 Portici, Italy, † ENEA Centro Ricerche Casaccia “UTAGRI - ECO”, Via Anguillarese 301, 00123 Santa Maria di Galeria, Roma, Italy, ‡ Istituto di Ricerche sulle Attivit` a Terziarie - CNR, Via M. Schipa 91, 80122 Napoli, Italy, and § Dipartimento di Matematica e Statistica, Universit` a degli Studi di Napoli ‘Federico II’, Via Cintia, 80126 Napoli, Italy Abstract 1 The cynipid gall wasp Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae) is an invasive wasp in Europe and is one of the major pests of chestnuts worldwide. An investigation of this cynipid was started in Campania, Southern Italy, in 2008, with the aim of providing guidelines for its sustainable control. 2 The number of larvae/gall increased in the second year of colonization relative to the first one but thereafter decreased in the third year of colonization, whereas the volume of the galls after the initial increase in the second year of colonization became stable. Adult emergence generally peaked between the middle of June and July. 3 The only reliable method for assessing the presence of the pest at its earliest stage was through dissecting the buds because oviposition scars on the buds tended to disappear during the winter. 4 Yellow traps were shown to be an effective method for assessing the emergence of cynipid adults and could potentially be used to time chemical applications in those cases in which this control method is feasible. 5 No correlation was recorded between the relative durations of the final stages (pupae, pharate adults and emergence). 6 Possible control strategies for this invasive pest are discussed. Keywords Biological invasion, buds, Campania, chestnut gall wasp, copse wood, Cynipidae, fruit orchards, Hymenoptera, phenology, sticky traps. Introduction Italy hosts the largest number of alien Hymenoptera species in Europe (Rasplus et al., 2010). One of the more recent invasive species to arrive in Italy is the cynipid gall wasp Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae), a major pest of chestnut species [Castanea spp. (Fagaceae)]. In its area of origin (China) and neighbouring countries (Japan, Korea), D. kuriphilus has resulted in massive reductions in the local yields of different species of chestnut [Castanea mollissima Blume, Castanea henryi (Skan) (but see also Lu et al., 2012), Cas- tanea crenata Siebold and Zuccarini] over the last five decades (Yasumatsu, 1951; Murakami et al., 1995; Abe et al., 2007; Correspondence: Umberto Bernardo. Tel.: +3 908 177 53658; fax: +39 081 775 5872; e-mail: bernardo@ipp.cnr.it Fan & Zhu, 2010). In 1974, D. kuriphilus was recorded on a Chinese chestnut in the U.S.A. (Payne et al., 1975). In 2002, it was introduced into Europe and colonized the European chest- nut Castanea sativa Miller (Aebi et al., 2007; Graziosi & Santi, 2008; Zhang et al., 2009). The level of damage on this new ‘host’ plant appears to depend on the cultivar (Botta et al., 2006; Panzavolta et al., 2012). Italy is the second largest European producer of the European chestnut (after Turkey), placing it fourth in the world ranking (Ingino et al., 2006). More than 40% of Italian pro- duction is in Campania (Southern Italy), with the Province of Avellino contributing to almost 50% of the regional production (Ingino et al., 2006). In 2005, D. kuriphilus was accidentally introduced into Campania from Piedmont on nursery plants that had heavily-infested buds (Graziosi & Santi, 2008). Subse- quently, the cynipid has spread throughout the region, moving  2012 The Royal Entomological Society