Inspection of Consignments for Xylella Fastidiosa
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Bulletin OEPP/EPPO Bulletin (2020) 50 (3), 401–414 ISSN 0250-8052. DOI: 10.1111/epp.12690 European and Mediterranean Plant Protection Organization Organisation Europe´enne et Me´diterrane´enne pour la Protection des Plantes PM 3/81(2) Phytosanitary procedures PM 3/81 (2) Inspection of consignments for Xylella fastidiosa Specific scope Specific approval and amendment This Standard describes the procedures for inspection of First approved in 2016–09. Revision approved in 2020-09. consignments for detection of Xylella fastidiosa on host plants. All potential host plants have been considered as well as insects which are vectors of the pest. The Standard can be applied to phytosanitary import inspection, including sampling and identification of symptoms. The Standard does not state what phytosanitary action should be taken in response to finding the pest, but may indicate where, for example, a consignment should be held pending a test result (EPPO, 2009). province of Alicante in mainland Spain (mainly on Prunus 1. Introduction dulcis) (EPPO, 2020) constitutes an important expansion of Xylella fastidiosa (EPPO Code XYLEFA) (Wells et al., its geographical distribution and also adds new host plants. 1987) is listed as an EPPO A2 pest and is a regulated pest Furthermore, in 2019, X. fastidiosa was detected for the in the European Union (EU, 2019/2072), and in several first time in Israel on P. dulcis (EPPO, 2019). EPPO countries (EPPO, 2020). X. fastidiosa is a xylem-lim- There are three accepted subspecies of X. fastidiosa, ited plant pathogen considered to cause several diseases in fastidiosa, pauca and multiplex (Schaad et al., 2004), on a wide range of cultivated and wild host plants, especially the basis of DNA–DNA hybridization data, although only in North, Central and South America (Janse & Obradovic, two, subspecies fastidiosa and multiplex, are so far consid- 2010; EFSA, 2015). Outside the Americas, diseases associ- ered valid names by the International Society of Plant ated with X. fastidiosa have been reported in Taiwan, caus- Pathology Committee on the Taxonomy of Plant Pathogenic ing symptoms of Pierce’s disease in commercial vineyards Bacteria (ISPP-CTPPB) (Bull et al., 2012). The subspecies (Vitis vinifera) (Su et al., 2014). Symptoms similar to cause different diseases on different plants and have differ- Pierce’s disease were reported from vineyards and almond ent geographical distributions (EFSA, 2015). The bacterium orchards in several provinces of Iran in 2014 (Amanifar is the causal agent for Pierce’s disease of grapevine, et al., 2014). Since 2013, the bacterium has been found in almond leaf scorch, alfalfa dwarf, oak leaf scorch, maple aged olive trees (Olea europaea) affected by extensive leaf leaf scald, sycamore leaf scorch, mulberry leaf scorch, peri- scorch and dieback, and in a range of other hosts in the winkle wilt, pecan leaf scorch, elm leaf scorch, oleander Salento Peninsula (Puglia region, Southern Italy) (Nigro leaf scorch, phony peach, plum leaf scald, citrus variegated et al., 2013; Saponari et al., 2013). The outbreak of chlorosis and coffee leaf scorch (Hopkins & Purcell, 2002). X. fastidiosa in olive trees in Southern Italy (Saponari Various subspecies of the bacterium have been genetically et al., 2013; Martelli et al., 2016) and the presence of the identified and sequenced, and some strains, including the bacterium in Mediterranean plant species, e.g. in Nerium CoDiRO strain of X. fastidiosa subsp. pauca found on oleander and Polygala myrtifolia, in the natural and urban O. europaea and other species in Puglia (IT) as well as landscape of Southern Italy, Corsica, along the eastern part X. fastidiosa subsp. pauca strains found in intercepted con- of the Mediterranean coast in France, Tuscany, the Balearic signments of Coffea plants in the Netherlands, have been Islands, the north of Portugal and in a limited area of the completely sequenced (Giampetruzzi et al., 2015; Potnis ª 2020 OEPP/EPPO, Bulletin OEPP/EPPO Bulletin 50, 401–414 401 402 Phytosanitary procedures et al., 2019). For the occurrence of the different subspecies X. fastidiosa does not always cause visible symptoms in in all affected countries in the EU refer to EU (2020a) host plants. In Salento (Southern Puglia region, Southern (https://ec.europa.eu/food/plant/plant_health_biosecurity/leg Italy), the CoDiRO strain of X. fastidiosa has been detected islation/emergency_measures/xylella-fastidiosa/latest-devel on olive trees and other hosts, such as oleander (Nerium opments_en). oleander), almond (P. dulcis) and cherry (P. avium), including both ornamental and wild plants. In France, X. fastidiosa subsp. multiplex has been detected on 1.1. Vectors of X. fastidiosa Polygala myrtifolia and many other ornamentals and Euro- Insects belonging to the order Hemiptera, suborder Auchen- pean plant species. In Portugal (Porto), X. fastidiosa subsp. orrhyncha (Redak et al., 2004), that feed on xylem sap multiplex has been detected on olive and plant species typi- (Chatterjee et al., 2008) are considered as potential vectors cal for the Mediterranean area. In Spain, in the Balearic of X. fastidiosa. Vectors that acquire X. fastidiosa as adults Islands, all three subspecies have been detected and host remain infective for life (Purcell et al., 2014). plants include wild and cultivated olive trees, vines and In the Americas, numerous species of xylem sap-sucking almond. In mainland Spain (Alicante), almond and host Hemiptera from the families Cicadellidae, Aphrophoridae plants typical to the Mediterranean area have been reported and Cercopidae (Auchenorrhyncha) are known to be vectors as hosts. In Israel, X. fastidiosa subsp. fastidiosa has been of X. fastidiosa (Redak et al., 2004). The non-European reported on almond. species Carneocephala fulgida, Draeculacephala minerva, In general, trees, shrubs or perennial host plant species Graphocephala atropunctata and Homalodisca vitripennis are a high risk for the introduction and spread of the dis- are known to be vectors of X. fastidiosa, and the latter is ease. A detailed list of plants known to be susceptible to listed as an EPPO A1 pest. Non-European Cicadellidae the European and non-European isolates of X. fastidiosa is known to be vectors of Pierce’s disease are also included in reported in the Commission Implementing Regulation (EU) Annex IIA of the Commission Implementing Regulation 2020/1201 (EU, 2020b) (https://eur-lex.europa.eu/legal-con (EU) 2019/2072 (EU, 2019) and in the plant health provi- tent/EN/TXT/PDF/?uri=CELEX:32020R1201&from=EN) sions of other EPPO countries. and in a database from EFSA (2020). In the EPPO region, Philaenus spumarius has been con- firmed as a vector of X. fastidiosa to olive, and likely other 1.3. Symptom description host plants, in the Southern Italian outbreak of the bac- terium (Saponari et al., 2014; Cornara et al., 2017a,b). Symptoms depend on the particular combination of host and More recently, Philaenus italosignus and Neophilaenus X. fastidiosa strain. As the bacterium invades xylem vessels campestris have also been confirmed to be vectors of it blocks the transport of mineral nutrients and water. Symp- X. fastidiosa subsp. pauca ST53 to olive plants under toms observed include leaf scorching, wilting of the foliage, experimental conditions (Cavalieri et al., 2019). Cicadidae defoliation, chlorosis or bronzing along the leaf margin and and Tibicinidae species in the EPPO region should also be dwarfing. Bacterial infections can be so severe as to lead to considered as potential vectors (EFSA, 2019), although the death of the infected plant. Symptoms usually appear on Cornara et al. (2020) found no evidence for a role of Cica- just a few branches but later spread to cover the entire plant. das in the epidemiology of X. fastidiosa. EFSA (2019) lists Symptoms can be confused with those caused by other bio- potential European vectors drawn from the Fauna Europaea tic or abiotic factors (other pathogens, environmental stres- database (de Jong, 2013, see also Albre & Gibernau, 2019; ses, water deficiency, salt, air pollutants, nutritional Morente et al., 2018). problems, sun burn, etc.); illustrations of such symptoms can be seen at https://agriculture.gouv.fr/telecharger/ 85855?token=8a019ac3c15b6da65ed2ad3559265bc7. 1.2. Host plants concerned Symptoms most commonly seen in the EPPO region X. fastidiosa has an extensive natural host range, which include bronzing, which may intensify before browning and includes many herbaceous and woody plants, cultivated drying (Janse & Obradovic, 2010). Depending on the plant crops and weeds. The range includes the following woody species, yellow spots on leaves, chlorotic foliage (often plants: species of Citrus, Juglans, Magnolia, Olea, Prunus together with pronounced yellow discoloration between and Vitis. The EFSA database (EFSA, 2020) includes 595 healthy and necrotic tissues), irregular lignification of bark, plant species reported to be infected by X. fastidiosa,of stunting, premature leaf drop, reduction of production and which for 343 plant species the infection has been deter- dimension of fruits, fruit distortion, crown dieback or a mined with at least two different detection tests. These spe- combination of symptoms may occur. cies cover hundreds of host plant genera in 85 botanical Symptoms on various hosts can be seen in https://gd.e families (64 botanical families when considering only ppo.int/taxon/XYLEFA/photos. Symptoms of diseases asso- records with at least two different detection methods). The ciated with X. fastidiosa in Europe and in the Americas are list of hosts in Europe is regularly updated with the results presented in Appendix 1 (in alphabetical order of disease of official surveys (EU, 2019). The presence of name). ª 2020 OEPP/EPPO, Bulletin OEPP/EPPO Bulletin 50, 401–414 PM 3/81 (2) Inspection of consignments for Xylella fastidiosa 403 Additionally, illustrations of possible symptoms can be 3. Inspection of host plants seen at: (1) https://www.xfactorsproject.eu/wp-content/uploads/ 3.1. Selection of plants for inspection 2018/01/Photo-Gallery-of-symptoms-caused-by-xylella- Visual observations are not always sufficient for the detec- in-Spain.pdf tion of X.