Pest categorisation of non-EU Scolytinae on non-coniferous hosts

Abstract

The EFSA Panel on Plant Health performed a group pest categorisation for the EU territory of non-EU Scolytinae (Coleoptera: Curculionidae) on non-coniferous hosts, which total 6495 known species. Most species attack apparently healthy, weakened or dead trees, either feeding on the phloem ('bark beetles' subgroup) or on fungi inoculated into the sapwood ('ambrosia beetles' subgroup). Smaller subgroups feed and reproduce in seeds and fruits, or in herbaceous plants. Some species are polygynous, the males initiate a gallery or a chamber on or in a new host and attract females. Others are monogamous, and the females initiate the new galleries. Many species respond to primary volatile attractants emitted by the hosts, and some produce aggregation pheromones that attract conspecifics of both sexes. The species attacking living hosts are often associated with fungi that contribute to weakening the host defences and provide nutrients to the insects. Some are inbreeding; the males in the offspring mate with their sisters and rarely leave their natal tree. The larvae of all species develop and pupate within their hosts. Based on catalogues and other published data, a database was constructed providing information on hosts, feeding and reproductive habits, geographic distribution and the Köppen-Geiger climate types in countries where species occur. The Scolytinae were screened to exclude species in the following categories: (i) 708 species attacking conifers; (ii) 127 species present in at least four EU Member States and (iii) 440 species occurring in areas with climatic conditions not occurring in the EU. Among the remaining 5220 species, 88 species known for their mobility, occupying at least two landmasses separated by geographical barriers and some of which had impact levels documented in literature, were extracted. They were grouped into four subcategories: (i) 12 species with high impact on plant health; (ii) 16 species with low or doubtful impact; (iii) 48 species with no impact; (iv) 12 species with no impact and which had never been recorded as 'introduced' in the consulted catalogues but occurring on at least two landmasses. All 88 species could enter the EU with wood or wood products, or with plants for planting, and could establish because host plants are available, and climate is suitable in parts of the EU. Control measures to inhibit introduction are available. There is considerable uncertainty regarding the potential impact of many species. Methods for the reliable identification of many species are lacking. For some species of non-EU Scolytinae on non-coniferous hosts, all criteria assessed by EFSA for consideration as potential quarantine pest are met. Nevertheless, the Panel was not able to develop a method to discriminate confidently between species that clearly meet the criteria for potential quarantine pest status and those that do not.

Keywords: ambrosia beetles; bark beetles; broadleaf; pest risk; plant health; plant pest; quarantine.

FIGURE 1

Decision tree to support the categorisation of Scolytinae (numbers in brackets indicate the number of species).

FIGURE 2

Global distribution of non‐EU Scolytinae on non‐coniferous hosts (Source: Literature; for details see Appendix B).

FIGURE 3

Number of non‐EU Scolytinae species on non‐coniferous hosts reported exclusively from one continent.

FIGURE 4

Number of non‐EU Scolytinae species on non‐coniferous hosts distributed in world continents.

FIGURE 5

EU annual imports on non‐coniferous wood (selected HS codes) from the world's biogeographic realms (in million tonnes).

FIGURE 6

The distribution of European broadleaf forests (data source: CORINE Land Cover, 2018).

FIGURE 7

(a) Plot distribution and simplified chorology map for Quercus robur. Frequency of Quercus robur occurrences within the field observations as reported by the National Forest Inventories (Eaton et al., 2016). https://ies‐ows.jrc.ec.europa.eu/efdac/download/Atlas/pdf/Quercus_robur_petraea.pdf. (b) Plot distribution and simplified chorology map for Prunus avium. Frequency of Prunus avium occurrences within the field observations as reported by the National Forest Inventories (Welk et al., 2016). (c) Plot distribution and simplified chorology map for Ulmus glabra. Frequency of Ulmus glabra occurrences within the field observations as reported by the National Forest Inventories (Caudullo & de Rigo, 2016). (a–c) Plot distributions and simplified chorology maps for specific broadleaf tree (non‐coniferous) hosts of non‐EU Scolytinae.

FIGURE 8

Google Scholar citations against time for three scolytine species that recently established and caused damage in new territories.