Pest survey card on Geosmithia morbida and its vector Pityophthorus juglandis

Abstract

This pest survey card was prepared in the context of the EFSA mandate on plant pest surveillance (M-2017-0137) at the request of the European Commission. Its purpose is to guide the Member States in preparing data and information for Geosmithia morbida and Pityophthorus juglandis surveys. These are required to design statistically sound and risk-based pest surveys, in line with current international standards. Geosmithia morbida and its vector P. juglandis are clearly defined taxonomic entities and the combined activity of the fungus and the insect causes the disease complex thousand canker disease on the plant genera Juglans and Pterocarya. The pest and its vector originate in North America and currently have a restricted distribution in the EU, limited to the northern parts of Italy. However, they are potentially able to become established everywhere in the EU where their host plants occur. Currently, the spread capacity of P. juglandis is unknown, but the insect vector may cover large distances by passive dispersal or human-assisted spread. Risk locations include entry points (e.g. seaports, airports), loading stations, storage facilities and wood processing companies that deal with heat-treated wood, bark or woodchips of the genera Juglans and Pterocarya originating from countries where the fungus and its vector occur. Trapping is the recommended method for detecting the vector in the early stages of an epidemic. Following insect trapping, a specific tree inspection should be carried out, looking for external symptoms (e.g. penetration and exit holes, cankers and wilting). The trapping should start when the mean air temperature exceeds 18°C. Morphological identification of the pathogen and its vector should be performed by experts. Molecular assays are also available for both fungal and vector identification.

Dispersal and colonization risk of the Walnut Twig Beetle, Pityophthorus juglandis, in southern Europe

“…The model shows WTB preference for black walnut (J. nigra) over English walnut (J. regia), consistent with the literature (Newton and Fowler 2009;Wilstermann et al 2020). In the sites monitored during this study, more than 45% of black walnut orchards were attacked by WTB, compared to 29% of English walnut orchards.…”

Rapid Detection of Pityophthorus juglandis (Blackman) (Coleoptera, Curculionidae) with the Loop-Mediated Isothermal Amplification (LAMP) Method

“…Morphological identification can therefore be technically demanding, requiring time and expert personnel. Moreover, when a large number of samples have to be examined, these checks take on a greater weight [15]. Efficient, high-performance molecular diagnostic methods that provide accurate non-morphological identification of WTB would offer new opportunities for effectively managing this EU-regulated pest complex.…”

“…Adult morphological identification requires entomological experience, as is the case with many small-sized bark beetles. The morphological identification is even more troublesome for the preimaginal stages, which are indistinguishable from other similar-sized bark-beetle larvae [15]. Many of the issues related to WTB are common to those of other wood-boring beetles of quarantine significance.…”

Thousand Cankers Disease in Walnut Trees in Europe: Current Status and Management

“…It bores galleries in the phloem of its hosts, especially colonizing the lower portion of the branches that are less exposed to thermal excursions [ 28 ], particularly those with a diameter greater than 3 cm. However, with high insect population densities, the medium–high portions of the trunk can also become infested [ 3 , 29 ]. It is also able to attack seedlings [ 30 ]; however, no TCD infestations on nursery stock have been reported [ 3 ].…”

“…According to WTB behavior, the symptoms occur initially on the lower portion of the branches [ 28 ], especially those with a diameter greater than 3 cm [ 38 ]. Later they spread to the medium-high portions of the trunk [ 3 , 29 ]. In addition, cracks sometimes form on the bark of the small-diameter branches near the tunnels, which gives the branches a rough appearance.…”