Risk to plant health in the EU territory of the intentional release of the bud-galling wasp Trichilogaster acaciaelongifoliae for the control of the invasive alien plant Acacia longifolia

Abstract

The EFSA Panel on Plant Health was requested by the European Commission to assess the risk to plant health in 8the European Union if the Australian bud-galling wasp Trichilogaster acaciaelongifoliae was released for the 9control of the invasive alien plant Acacia longifolia in Portugal. T. acaciaelongifoliae feeds on A. longifolia and 10A. floribunda. In South Africa, following its intentional introduction in 1982 and 1983, the wasp is now present 11throughout the range of A. longifolia in that country, with most plants showing galls and seed set reductions of, 12initially, up to 95 %. Climatic conditions in the EU are largely suitable for establishment wherever A. longifolia13and A. floribunda are present. T. acaciaelongifoliae is moderately likely to establish and spread in the EU, by 14natural means, but particularly if it is intentionally moved to control populations of A. longifolia other than those 15present in Portugal. The effects on native biodiversity and ecosystems resulting from invasive populations of 16A. longifolia are likely to be reduced by the wasp. A. longifolia is grown as an ornamental plant in some EU 17countries. A. floribunda is not an invasive plant in the EU and is cultivated as an ornamental plant on a small 18scale in France, Greece and Italy. Any effects on cultivated ornamental A. longifolia and A. floribunda a re rated 19as moderate, although likely to be transient, as the industry could switch to the cultivation of other Acacia spp. 20For plant species other than A. longifolia and A. floribunda, consequences are expected to be minor, with low 21uncertainty except for A. retinodes and Cytisus striatus, where further investigation is required. No risk-reducing 22options in the plant health context are considered necessary, except for monitoring, sentinel planting, and care 23with regard to quarantine facilities and release protocols to prevent accidental release in situations and locations 24other than those intended