Cryphalus dilutus Eichhoff, 1878

Barnouin, Thomas, Soldati, Fabien, Roques, Alain, Faccoli, Massimo, Kirkendall, Lawrence R., Mouttet, Raphaëlle, Daubree, Jean-Baptiste & Noblecourt, Thierry, 2020, Bark beetlesand pinhole borers recently ornewly introduced toFrance (Coleoptera Curculionidae, Scolytinae and Platypodinae), Zootaxa 4877 (1), pp. 51-74 : 55-56

- Cryphalus dilutus Eichhoff

( Figs. 3A, 3B )

Nomenclatural note. Our specimens are the same species as that reported in previous literature for southern Europe ( Italy and Malta) as Hypocryphalus scabricollis . In a recent treatment of Hypocryphalus, Johnson et al. (2017) state that the Hypocryphalus from southern Europe, North Africa, Middle East and southern Asia is H. dilutus . Verifications carried out by authors on male specimens from France, Italy, Tunisia and Malta confirmed species identification. Indeed the males have a sharp, true (non-socketed) spine on the proximal face of the mesofemur, which is a unique character not described or observed in any other Hypocryphalus species, or even any other scolytine ( Johnson et al. 2017). This species is now placed in Cryphalus Erichson , the genus in which it was originally described ( Johnson et al. 2020).

Distribution. Described from and probably native to north of the Indian subcontinent ( Eichhoff 1878), C. dilutus is a highly successful invasive species newly intercepted in France. After Malta in 1991 ( Mifsud & Knižek 2009) and Sicily in 2014 ( Faccoli et al. 2016a), France is the third European country colonized by this species. On the Mediterranean rim, this species has recently been found in Tunisia ( Gaaliche et al. 2018) and Algeria ( INPV 2018). In Malta, the species has become common throughout the country ( Mifsud et al. 2012), while in Sicily it has been detected in eight localities in just two years ( Faccoli et al. 2016a). A thermophilic species, C. dilutus is preadapted to the Mediterranean climate. In France, it was captured in good numbers (30 individuals) in two municipalities of the peninsula of Saint-Tropez. Thus, available data suggest that this species is already established in France, though details of its distribution remain to be ascertained.

New records: VAR – Ramatuelle, bottle trap: 2 ind. from 02.VIII. to 22.VIII.2017 and 2 ind. from 27.IX. to 19.X.2017, DSF leg.; Ramatuelle, Pascasti, bottle trap, 05.VII. to 19.VII.2017, 1 ind., DSF leg.; Saint-Tropez, Salins, interception traps baited with ethanol 20%: 1 ind. from 24.III. to 12.IV.2017, 3 ind. from 05.VII. to 19.VII.2017, 4 ind. from 02.VIII. to 22.VIII.2017, 10 ind. from 13.IX. to 27.IX.2017 and 7 ind. from 27.IX. to 19.X.2017, DSF leg .

Biology and ecology. Cryphalus dilutus is a small bark beetle species that breeds in twigs, branches and trunks of the host trees and shrubs ( Cutajar & Mifsud 2017). It attacks stressed or dying trees as well as healthy individuals ( Cutajar & Mifsud 2017; Gaaliche et al. 2018). Johnson et al. (2017) found there to be two slightly divergent clades of C. dilutus , one developing in mango ( Mangifera indica L.) and the other in several species of fig trees. In Malta, the fig clade of this species was probably introduced via international trade of Ficus retusa L., a species imported from Asia frequently used as an ornamental tree along roads and in the Maltese gardens ( Mifsud & Knižek 2009). C. dilutus was found infesting several fig species on the Maltese island ( Ficus macrocarpa L., F. retusa and F. carica L.) ( Mifsud & Knižek 2009; Mifsud et al. 2012). In Sicily, it develops on both wild and cultivated common fig ( F. carica ) ( Faccoli et al. 2016a). Data from Tunisia confirm the common fig as a C. dilutus host in the Mediterranean Basin ( Gaaliche et al. 2018). Thus, these data support the hypothesis that the C. dilutus in France belong to the Ficus -breeding lineage.

Damage and infestation risk. Massive infestations of C. dilutus cause a host dieback resulting in the partial drying of the main branches and leave yellowing. Rapidly, the whole tree is affected with sap flow and bark cracks visible at the base of the trunk ( Cutajar & Mifsud 2017; Gaaliche et al. 2018). The dieback leads to tree death, which mainly affects old trees regardless of their vigor ( Gaaliche et al. 2018). In Malta, more than 50% of the fig trees infested by this insect died between 2011 and 2017, which led the authorities to implement a monitoring and a control program against this species ( Cutajar & Mifsud 2017). As France is the fourth largest producer of figs in Europe, this pest represents a major threat to this fruit tree.

Figures

FIGURE 3. Cryphalus dilutus Eichhoff (1.8 mm).A. dorsal view; B. lateral view. Xylosandrus compactus (Eichhoff) (1.7 mm). C. dorsal view; D. lateral view. Xylosandrus crassiusculus (Motschulsky) (2.6 mm). E. dorsal view; F. lateral view. Length of specimens in brackets. (Photos: Fabien Soldati & Thomas Barnouin).