Coexistence of Xylosandrus crassiusculus (Motschulsky) and X. compactus (Eichhoff) (Coleoptera Curculionidae Scolytinae) in the National Park of Circeo (Lazio, Italy).
In 2016, a widespread dieback of several plant species was noted in the National Park of Circeo and in the neighbouring areas of Lazio. Further investigation of etiological symptoms led to the identification of two exotic scolytid species: Xylosandrus crassiusculus (Motschulsky) collected on the carob tree Ceratonia siliqua, and Xylosandrus compactus (Eichhoff) collected on Quercus spp., Laurus nobilis, Acer pseudoplatanus, Liquidambar styraciflua, Ficus carica and Magnolia grandiflora. In Italy, X. crassiusculus was reported for the first time in 2003 in pine-mixed woods of Tuscany. Moreover, since 2011, the congeneric species X. compactus has been also recorded on some ornamental plants in Campania, on Ceratonia siliqua in Sicily and on Laurus nobilis in Tuscany and Liguria. In the present work, taxonomic keys of the four Xylosandrus species introduced into Europe were provided together with data on their essential morphological and bio-ecological features with particular emphasis on X. crassiusculus and X. compactus. Furthermore, since X. crassiusculus and X. compactus are vectors of pathogenic fungi such as Fusarium solani, a special focus was placed on their control measures.