Pest categorisation of Arceuthobium spp. (non-EU)

Abstract

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of Arceuthobium spp. (non-EU), a well-defined and distinguishable group of parasitic plant species of the family Viscaceae, also known as dwarf mistletoes. These are flowering plants parasitising a wide range of conifers of the families Pinaceae and Cupressaceae. Arceuthobium species (non-EU) are regulated in Council Directive 2000/29/EC (Annex IAI) as harmful organisms whose introduction into the EU is banned. Many Arceuthobium species are recognised, with most dwarf mistletoes native in the New World, and north-western Mexico and the western USA as the centre of diversity for the genus. Only two Arceuthobium species are native (and reported to be present) in the EU (Arceuthobium azoricum and Arceuthobium oxycedrum), which are thus not part of this pest categorisation. Hosts of non-EU dwarf mistletoes include species of the genera Abies, Cupressus, Juniperus, Larix, Picea, Pinus, Pseudotsuga and Tsuga. Most Arceuthobium spp. can parasitise more than one species of conifer host. Dwarf mistletoes could enter the EU via host plants for planting and cut branches, but these pathways are closed. They could establish in the EU, as hosts are widespread and climatic conditions are favourable. They would be able to spread following establishment by human movement of host plants for planting and cut branches, as well as natural spread. Should non-EU dwarf mistletoes be introduced in the EU, impacts can be expected on coniferous woodlands, plantations, ornamental trees and nurseries. The main uncertainties concern (i) the precise distribution and host range of the individual Arceuthobium spp. and (ii) the level of susceptibility of conifers native to Europe. For Arceuthobium spp. (non-EU) as a group of organisms, the criteria assessed by the Panel for consideration as a potential quarantine pest are met, while, for regulated non-quarantine pests, the criterion on the pest presence in the EU is not met.