Pest categorisation of Neoscytalidium dimidiatum

Abstract

The EFSA Plant Health Panel performed a pest categorisation of Neoscytalidium dimidiatum, a clearly defined plant pathogenic fungus of the family Botryosphaeriaceae. The pathogen affects a wide range of woody perennial crops and ornamental plants causing symptoms such as leaf spot, shoot blight, branch dieback, canker, pre- and post-harvest fruit rot, gummosis and root rot. The pathogen is present in Africa, Asia, North and South America, and Oceania. It has also been reported from Greece, Cyprus and Italy, with a restricted distribution. Nevertheless, there is a key uncertainty on the geographical distribution of N. dimidiatum worldwide and in the EU, because in the past, when molecular tools were not available, the two synanamorphs of the pathogen (Fusicoccum-like and Scytalidium-like) might have been misidentified based only on morphology and pathogenicity tests. N. dimidiatum is not included in Commission Implementing Regulation (EU) 2019/2072. Because of the wide host range of the pathogen, this pest categorisation focuses on those hosts for which there is robust evidence that the pathogen was formally identified by a combination of morphology, pathogenicity and multilocus sequence analysis. Plants for planting, fresh fruits and bark and wood of host plants as well as soil and other plant growing media are the main pathways for the further entry of the pathogen into the EU. Host availability and climate suitability factors occurring in parts of the EU are favourable for the further establishment of the pathogen. In the areas of its present distribution, including Italy, the pathogen has a direct impact on cultivated hosts. Phytosanitary measures are available to prevent the further introduction and spread of the pathogen into the EU. N. dimidiatum satisfies the criteria that are within the remit of EFSA to assess for this species to be regarded as potential Union quarantine pest.

Keywords: N. hyalinum; N. orchidacearum; Neoscytalidium novaehollandiae; pest risk; plant health; plant pest; quarantine.

Figure 1

Morphological characteristics of Neoscytalidium dimidiatum on Hylocereus polyrhizus: (a) & (b) 3‐day‐old colony on PDA in top and bottom view, respectively, (c) 4‐week‐old colony on PDA developed small black conidiomata (arrow), (d) zoom view of conidiomata, (e) hyphae and phragmospores (arthroconidia), (f) pycnidia developed on dried Napier grasses, (g) conidiogenous cells and (h) conidia (pycnidiospores (from Dy et al., 2022)

Figure 2

Global distribution of Neoscytalidium dimidiatum [Data Source: CABI CPC (online; last accessed on 1/2/2023), Farr and Rossman (online; last accessed on 1/2/2023) and other literature sources]. The presence of the pathogen in Greece and Cyprus is uncertain

Figure 3

Distribution of 10 Köppen–Geiger climate types, i.e. Bsh, Bsk, Cfa, Cfb, Cfc, Csa, Csb, Csc, Dfb and Dfc that occur in the EU and in third countries where Neoscytalidium dimidiatum has been reported. The legend shows the list of Köppen–Geiger climates. Red dots indicate point locations where N. dimidiatum was reported.