Pest categorisation of Listronotus bonariensis

Argentine stem weevil, grass seed, pasture, pest risk, plant health, plant pest
First published in the EFSA Journal
10 January 2018
23 November 2017
Scientific Opinion


The Panel on Plant Health performed a pest categorisation of Listronotus bonariensis (Coleoptera: Curculionidae), the Argentine stem weevil, for the EU. L. bonariensis is a well-defined species, recognised as a serious pest of pasture grasses, especially Lolium spp. and Poa annua, in New Zealand, and a rare pest of cereals in Argentina, Brazil and New Zealand. Larvae feed within the tillers and stems of grasses; adults can cut emerging cotyledons although they usually graze on leaves. Larval damage is most serious. Larval feeding causes a reduction in pasture quality that impacts on the production of grazing animals. L. bonariensis is not known to occur in the EU and is listed in Annex IIAI of Council Directive 2000/29/EC. L. bonariensis established in New Zealand via imported grass seeds and has been intercepted on grass seeds entering the EU. Considering the climatic similarities of the regions where the pest occurs and the very great extent to which hosts are grown across the EU, L. bonariensis has the potential to establish within the EU with two or three generations possible per year. Impacts could occur in grassland pastures and perhaps occasionally in cereals. In New Zealand, endophytic fungi occurring on potential hosts deter L. bonariensis from ovipositing on leaves and are toxic to larvae. Whether endophytic fungi on grasses in Europe could provide some resistance to L. bonariensis is uncertain. Phytosanitary measures are available to reduce the likelihood of introduction of this weevil. L. bonariensis fits all of the criteria assessed by EFSA to satisfy the definition of a Union quarantine pest. L. bonariensisdoes not meet the criterion of occurring in the EU territory for it to be regarded as a Union regulated non-quarantine pest.

Panel members at the time of adoption

Claude Bragard, David Caffier, Thierry Candresse, Elisavet Chatzivassiliou, Katharina Dehnen-Schmutz, Gianni Gilioli, Jean-Claude Grégoire, Josep Anton Jaques Miret, Michael Jeger, Alan MacLeod, Maria Navajas Navarro, Björn Niere, Stephen Parnell, Roel Potting, Trond Rafoss, Vittorio Rossi, Gregor Urek, Ariena Van Bruggen, Wopke Van der Werf, Jonathan West and Stephan Winter.
Panel on Plant Health
alpha [at]
EFSA Journal 2018;16(1):5101
Question Number
On request from
European Commission