SHORT COMMUNICATION Are the palms Washingtonia filifera and Chamaerops humilis suitable hosts for the red palm weevil, Rhynchophorus ferrugineus (Col. Curculionidae)? O ´ . Dembilio 1 , J. A. Jacas 2 & E. Lla ´ cer 1 * 1 Institut Valencia ` d’Investigacions Agra ` ries (IVIA), Montcada, Spain 2 Universitat Jaume I (UJI); Departament de Cie ` ncies Agra ` ries i del Medi Natural, Castello ´ de la Plana, Spain The invasive red palm weevil, Rhynchophorus ferru- gineus (Olivier) (Coleoptera: Curculionidae), has become the major pest of palms in the Mediterra- nean (EPPO 2008a). Females lay their eggs at the base of the fronds in separate holes made with their rostrum. Neonate larvae bore into the palm core and upon completion of development move back to the base of the fronds to pupate. A new generation emerges and these adults may remain within the host and reproduce until the palm dies. Rhynchophorus ferrugineus has been reported on 19 palm species belonging to 15 different genera (Bar- ranco et al. 2000; EPPO 2008a). Chamaerops humilis L., one of the two palm species native to Europe was considered resistant to R. ferrugineus (Barranco et al. 2000). Nevertheless, the European Union included this species in the list of R. ferrugineus susceptible plants (OJEU 2008). This list also included the genus Washingtonia spp. However, in assays carried out in 2007 (same authors, unpublished data), Washingtonia filifera (Lindl.) Wendl. could not be infested with R. ferrugineus whereas W. robusta H. Wendland could. Antibiosis, antixenosis, and tolerance are the three modes of plant resistance to insects (Painter 1951; Kogan and Ortman 1978; Wiseman 1999). Antibiosis describes a situation in which the insect’s normal relationship with a host plant causes physiological or developmental detriment to the insect. Antixenosis describes resistance in which the insect is either repelled from or not attracted to its normal host. Finally, tolerance characterizes plants with normal yields in presence of a damage that would affect the yield of non-tolerant plants. This study was undertaken to elucidate whether antibiosis or antixenosis against R. ferrugineus occur in C. humilis and W. filifera. Material and Methods The assays were carried out in summer 2008 in a mesh enclosure containing 24 independent screened cages (4 · 3 · 3 m) under natural light and temperature conditions (mean: 23.4°C max: 35.7°C min: 12.9°C). Plant material Trials were performed on 2-year-old potted palms of W. filifera, and C. humilis. Phoenix canariensis hort. ex Keywords Phoenix canariensis, antibiosis, antixenosis Correspondence Josep A. Jacas (Corresponding author), Unitat Associada d’Entomologia Agrı ´cola UJI-IVIA, Universitat Jaume I (UJI), Departament de Cie ` ncies Agra ` ries i del Medi Natural, Campus del Riu Sec, E-12071-Castello ´ de la Plana, Spain. E-mail: jacas@camn.uji.es *All authors contributed equally to this paper. Received: October 16, 2008; accepted: January 2, 2009. doi: 10.1111/j.1439-0418.2009.01385.x Abstract The red palm weevil, Rhynchophorus ferrugineus (Olivier) (Coleoptera, Curculionidae), is a widely distributed pest which has recently become the major pest of palms in the Mediterranean Basin. This weevil has been recorded on 19 different palm species, however, the host status of Washingtonia filifera and Chamaerops humilis remains unclear. The present study was carried out to check whether these species had either antixe- notic or antibiotic mechanisms of resistance against this pest. Our results show that both W. filifera and C. humilis are resistant to R. ferrugineus. Resistance in W. filifera is based on antibiosis whereas in C. humilis resis- tance is based on antixenosis. J. Appl. Entomol. J. Appl. Entomol. 133 (2009) 565–567 ª 2009 Blackwell Verlag, GmbH 565