Evaluation of the risk that kiln-dried walnut wood could be colonized by Pityophthorus juglandis (vector of Geosmithia morbida)
The fungus Geosmithia morbida and its vector Pityophthorus juglandis (Coleoptera: Scolytidae - walnut twig beetle) are the causal agents of the thousand cankers disease (EPPO A2 List) of walnut trees (Juglans spp.) in the USA and in Italy (recent introduction). Earlier studies had demonstrated that P. juglandis adults were able to enter and re-emerge from the bark of kiln-dried black walnut (J. nigra) slabs that were baited with a pheromone and hung in branches of infested J. nigra trees (Audley et al., 2016). Considering that this experiment represented extreme conditions which were unlikely to occur during wood production and transport, further studies were conducted to continue evaluating the risk of P. juglandis colonizing kiln-dried walnut wood (Mayfield et al., 2018). Comparisons were made between kiln-dried and fresh walnut slabs by varying both the presence of the aggregation pheromone and relative proximity to a beetle source (i.e. slabs placed on the ground or in the crown of a walnut tree). Results obtained indicated that kiln-dried bark was unsuitable for P. juglandis reproduction, and that the risk of kiln-dried walnut bark becoming colonized by P. juglandis during movement of commercial wood products was very low.
Sources
Audley J, Mayfield A, Myers S, Taylor A, Klingeman W (2016) Phytosanitary methods influence posttreatment colonization of Juglans nigra logs by Pityophthorus juglandis (Coleoptera, Curculionidae: Scolytinae). Journal of Economic Entomology 109(1), 213-221.
Mayfield AE III, Audley J, Camp R, Mudder BR, Taylor A (2018) Bark colonization of kiln-dried wood by the walnut twig beetle: effect of wood location and pheromone presence. Journal of Economic Entomology 111(2), 996-999.