Pest categorisation of Unaspis citri

Citrus snow scale, white louse scale, citrus, pest risk, plant health, plant pest, quarantine
First published in the EFSA Journal
7 March 2018
1 February 2018
Scientific Opinion


The Panel on Plant Health performed a pest categorisation of the citrus snow scale, Unaspis citri(Comstock) (Hemiptera: Diaspididae), for the European Union (EU). This is a well-defined and distinguishable species, native to south-eastern Asia, which has spread to many tropical and subtropical regions. U. citri can be a pest of citrus and has been cited on over 28 different species in 16 plant families. In the EU, U. citri occurs in the Azores. There is uncertainty as to whether it occurs in continental Portugal. Reports of it occurring in Greece and Spain are likely to be invalid and based on interception records from these countries. An old Italian record is a misidentification. U. citri is listed in Annex IIAI of 2000/29/EC as a harmful organism. The international trade of hosts, as either plants for planting, fruit or cut flowers, provide potential pathways into the EU. However, current EU legislation prohibits the import of citrus plants for planting from third countries. U. citri is mostly confined to coastal humid tropical areas and does not occur in semi-arid areas that are irrigated. Nevertheless, given that it occurs in the Azores and that there are regional climatic similarities between places where U. citri occurs and climates within the EU, and taking EU host distribution into account, U. citri has the potential to establish in the EU, especially in citrus-growing regions around the Mediterranean where losses in quality and yield of citrus could occur. Phytosanitary measures are available to inhibit the likelihood of introduction of U. citri. Considering the criteria within the remit of EFSA to assess the status as a potential Union quarantine pest (QP), or as a potential regulated non-quarantine pest (RNQP), U. citri meets the criteria assessed by EFSA for consideration as a potential Union QP.

Panel members at the time of adoption

Claude Bragard, David Caffier, Thierry Candresse, Elisavet Chatzivassiliou, Katharina Dehnen-Schmutz, Gianni Gilioli, Jean-Claude Gregoire, 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
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EFSA Journal 2018;16(3):5187
Question Number
On request from
European Commission