Dryocoetes himalayensis Strohmeyer

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 : 59

- Dryocoetes himalayensis Strohmeyer

( Figs. 1D, 1E )

Distribution. Native to the Himalayan regions of northern India, this species was introduced to Europe in the mid-1970s. It was detected for the first time in France in 1975 ( Knižek 2011a; Schott 2017) then in Switzerland in 1980, in the Czechia in 2009 ( Knižek 2011a) and recently in Germany ( Gebhardt & Bense 2016). D. himalayensis is considered to be established in Europe and is regularly found in Switzerland and the Czechia ( Foit et al. 2017). In France, D. himalayensis is already established and clearly expanding. Despite its rarity, this species is now well distributed in the eastern half of France, and has been collected in various habitats (forests, gardens and orchards), far from urban areas and potential sites of introduction. Although D. himalayensis responds weakly to the walnut twig beetle ( Pityophthorus juglandis Blackman ) pheromone, it has not been captured in Italy where a large monitoring program is set up annually in the main walnut plantations to survey the walnut twig beetle populations present in north Italy since 2013 ( Faccoli et al. 2016b).

Literature records: HAUT-RHIN – Heiwiller, 1.II.1975 ( Knižek 2011a; Schott 2017); SAVOIE – Challes-lesEaux, interception trap, from 20.V. to 04.VIII.2016, 7 ind. ( Dodelin 2016).

New records: ALLIER – Lalizolle, FD des Colettes, interception trap baited with ethanol 20%, 12.IV.2015, 1 ind., L. Velle leg.; DORDOGNE – Cazoulès , caught on English walnut, 08.X.2019, 2 ind., Fredon Aquitaine leg.; Coteaux Périgourdins , walnut orchard, interception trap baited with a pheromonal blend for the walnut twig beetle, 08.X.2019, 1 ind., J. Aubardier & M. Hoareau leg.; Montignac , caught on English walnut, 24.VII.2019, 2 ind., Fredon Aquitaine leg.; DROME – Laval-d’Aix, walnut orchard, interception trap with a pheromonal blend for the walnut twig beetle, 17.VI.2019, 1 ind., J.-L. Oddon leg.; Saint-Agnan-en-Vercors, RBI du Vercors, interception trap baited with ethanol 20%, from 22.V. to 05.VI.2012, 1 ind., ONF leg.; YVELINES – Andrésy, 16.VI.2005, 1 ind., E. Jiroux leg.; Vernouillet, interception traps baited with ethanol 100%, (-) α-pinene, and a pheromone blend for longhorn beetles, from 26.VII to 19.VIII.2016, 1 ind., URZF leg .

Biology and ecology. D. himalayensis is an oligophagous species reported in its native range only from English walnut ( Juglans regia L.) and pear ( Pyrus lanata D. Don ) ( Wood & Bright 1992). In Europe, reproduction of this species has been observed in the Czechia on black walnut ( Juglans nigra L.) ( Foit et al. 2017) and in France on English walnut ( Juglans regia L.), but it is suspected to also occur on oak ( Quercus ) ( Knižek 2011a). On black walnut, the species has never been observed on healthy plants, preferring dying or stressed trees ( Foit et al. 2017). A phloeophagous species, colonization is generally on the lower part of trunks (below 4 meters) of variable diameter. A black necrosis develops from the galleries and around the entrance holes ( Foit et al. 2017).

Damage and infestation risk. D. himalayensis seems to mainly be a secondary pest on black walnut ( Foit et al. 2017). Its role in the mortality of the attacked trees remains unclear and would require further investigations focused on the role of the associated fungi carried by this species and how it interacts with tree condition ( Foit et al. 2017).

Figures

FIGURE 1. Amasa sp. near truncata (Erichson) (2.5 mm). A. dorsal view; B. lateral view. Cyclorhipidion distinguendum (Eggers) (2.9 mm). C. dorsal view. Dryocoetes himalayensis Strohmeyer (2.7 mm). D. dorsal view; E. lateral view. Length of specimens in brackets. (Photos: Olivier Denux, Fabien Soldati & Thomas Barnouin).