PM 7/116 (1)Tetranychus evansi

Abstract

EPPO BulletinVolume 43, Issue 3 p. 425-430 Diagnostics DiagnosticFree Access PM 7/116 (1) Tetranychus evansi First published: 19 November 2013 https://doi.org/10.1111/epp.12060Citations: 2 Use of names of chemicals or equipment in these EPPO Standards implies no approval of them as others may also be suitable. AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Abstract Specific scope This standard provides guidance for the identification of Tetranychus evansi1. Specific approval and amendment Approved in 2013-09. Introduction Tetranychus evansi is a primary pest of Solanaceaous crops, but will also infest a variety of other hosts (Bolland et al., 1998). It originates from South America (Boubou et al., 2011) but has since spread, and is recorded in 39 countries (Migeon & Dorkeld, 2006). In EPPO countries, it is found in the Mediterranean area: Morocco, Algeria, Tunisia, Israel, Jordan, Greece (Crete), Italy, France, Spain (including Canary Islands and Balearic Islands) and Portugal (including Madeira). The first damages where observed in Brazil (Silva, 1954), Argentina (Rossi Simons, 1961), Mauritius (Moutia, 1958; Baker & Pritchard, 1960) and the United States (Wene, 1956). Tetranychus evansi is currently not considered as a pest in Southern America, but can be a highly destructive plant pest in Africa (Knapp et al., 2003a; Duverney & Ngueye-Ndiaye, 2005; Fiaboe et al., 2006), Spain (Ferragut & Escudero, 2002) and France (Migeon et al., 2009). Northward dispersion capabilities are limited by winter temperatures for this tropical and non diapausing species (Migeon et al., 2009) but it could occur in glasshouses as is the case for many tropical pests. The spider mite family (Tetranychidae), at present includes 1265 described species (Migeon and Dorkeld, 2006-2010) belonging to more than 70 genera. The genus Tetranychus is the third largest of the family with 148 species. Identity Name: Tetranychus evansi Baker & Pritchard, 1960. Synonyms: Tetranychus marianae nec McGregor, 1950 pro parte sensu Silva, 1954; misidentification, corrected by Moraes et al. 1987. Tetranychus takafujii Ehara & Ohashi 2002, synoymy by Gotoh et al., 2009. Taxonomic position: Arachnida: Acarina: Prostigmata: Tetranychidae. Common names: Red tomato spider-mite (English). EPPO code: TETREV. Phytosanitary categorization: EPPO A2 list no. 349. Detection Due to their minute size (about 0.5–0.6 mm in length for an average female adult) typical of many species of Acari, spider mites can remain undetected until major plant damage occurs. Mites live on both sides of the leaves with a slight preference for the underside and for the vicinity of the veins. Unlike others injurious Tetranychus species, such as Tetranychus urticae, this species has a relatively gregarious behaviour. Feeding causes the leaves to become chlorotic. The feeding activity of the mites causes white spots of dead parenchyma cells to appear on both leaf surfaces. Extensive silk webbing is also produced that can ‘mummify’ the host plant. In very heavy infestations the resultant webbing and persistent feeding activity eventually leads to the death of the host plant. While high densities are easily detected, low densities and early infestation i.e. the appearance of small and inconspicuous white spots may remain unnoticed or be mistakenly attributed to deficiencies, virus or fungal diseases. Mites can be observed with the naked eye or better with a magnifying glass or stereomicroscope, but detection can be more difficult on very hairy leaves such as aubergines. Mixed populations of T. evansi and other red or white species such as the common two-spotted spider mite Tetranychus urticae (Koch) can occur. Photos are presented in the EPPO gallery (http://photos.eppo.int/index.php/album/99-tetranychus-evansi-tetrev-). Identification Specific identification requires examination of slide mounted specimens of both an adult male and female, details on the preparation of slides are given in Appendix 1. Spider mite identification can be difficult and is reliant on a good knowledge of the group and previous experience. It is recommended (at least for a first identification or in case of doubt) that a specialist is consulted for confirmatory diagnosis or a complementary method should be performed (e.g. sequencing). An EPPO Standard PM 7/XX on DNA barcoding as an identification tool for plant pests is in preparation. Additional molecular information can be found in the Q-bank Arthropod database (http://www.q-bank.eu/arthropods/). Morphological characterization Family Tetranychidae Colour when alive varies from green to yellow, orange and red. The gnathosoma has a capsule-like structure, the stylophore, eversible with long slender whiplike chelicerae used for piercing parenchyma cells. Peritremes are simple or anastoming distally, arising from a pair of stigmata near the base of the stylophore. The palps are five segmented. Tarsus I and II usually have duplex setae. The ambulacrum has tenant hairs; the tarsal claws and empodia are either padlike or clawlike; the palpal tibia forms a clawlike complex with the palpal tarsus. Family descriptions, terms explanations and key to the genera can be found in major works (Jeppson et al., 1975; Gutierrez, 1985b; Meyer, 1987; Baker & Tuttle, 1994; Bolland et al., 1998). Genus Tetranychus Identification up to genus level can be done by examination of the empodium and setae pattern. The empodium does not bear tenent hair and is split distally in three pairs of hairs; The idiosoma bears 13 pairs of dorsal setae (prodorsum 3 and opisthosoma 10); One pair of para-anal setae and two pairs of anal setae are present. Species Tetranychus evansi Tetranychid mites develop through five stages: egg, larva, protonymph, deutonymph and adult. Active stages alternate with quiescent ones: protochrysalis, deutochrysalis and teleiochrysalis. Egg The eggs of T. evansi are indistinguishable from other spider mite eggs, they are rounded, orange hyaline to whitish, becoming grey before hatching. Larvae Larval stage is hexapodal i.e. has three pairs of legs. Nymph The two nymphal stages i.e. the protonymph and deutonymph like the adults have four pairs of legs. Nymphal stages can be paler than or the same colour as the adults i.e. varying from orange to brick-red or dark red. Adults There are no fully comprehensive keys to all the known species of the genus Tetranychus. Some regional works can be useful: Baker & Tuttle (1994) for North-America and Meyer (1987) for Africa. Flechtmann & Knihinicki (2002) give a key to majors groups of the genus based on females. Tetranychus evansi belong to the sub-genus Tetranychus s. str. and to the desertorum group that is characterized by Tarsus I having all 4 proximal tactile setae in line with proximal pair of duplex setae (3a & 3b). Within this group, the shape of the male aedeagus is the most important character used to discriminate species (Figs 5 and 6). Meyer's work on the spider mites of Africa is the most useful as it contains many of the tropical species encountered on Solanaceae, but can be difficult, particularly for the non-specialist. Because T. evansi can be difficult to separate from other morphologically similar species, it has been misidentified as T. marianae (in particular in Brazil, Argentina and USA), or as Tetranychus piercei in Taiwan and synonymized with T. takafujii in Japan. Morphological characters Female Body 500–600 μm long and 280–360 μm wide. From orange to brick-red or dark red; legs pale orange. Idiosoma with 13 pairs of dorsal setae (prodorsum 3 and opisthosoma 10) (Fig. 1), venter with 1 pair of para-anal setae and 2 pairs of anal setae (Fig. 1). Dorsohysterosomal striae longitudinal between setae e1 and between setae f1; forming a diamond shaped pattern between these two pairs of setae (Fig. 2). Peritremes hooked (Fig. 2). Tibia I with 9 tactile setae and 1 sensory seta (Fig. 3). Tarsus I with all proximal 4 tactile setae in line with proximal pair of duplex setae (Fig. 3). All empodia with 3 pairs of proximoventral hairs; empodium I with minute dorsal claw (Fig. 4c). Figure 1Open in figure viewerPowerPoint Tetranychus sp.: dorsoventral aspect of the female showing the body setae. The characteristics of the genus are indicated in red (modified from Gutierrez, 1985). Figure 2Open in figure viewerPowerPoint Tetranychus evansi: dorsal aspect of the female - Japan. Characteristics of the species are indicated in red (modified from Ehara & Ohashi, 2002). Figure 3Open in figure viewerPowerPoint Tetranychus spp. female tibia and tarsus I: variation of setae pattern on tarsus I. (A) T. evansi from Japan; (B) T. evansi from Mauritius; (C) T. marianae; (D) T. piercei. Red line top indicates proximal duplex setae, red line bottom indicates proximal tactile setae. (A) and (B) all proximal 4 tactile setae in line with proximal pair of duplex setae. (C) and (D) proximal pair of duplex setae distad of proximal tactile setae. (A) from Ehara & Ohashi, 2002; (B) from Baker & Pritchard, 1960; (C) from Pritchard & Baker 1955; (D) from Guttierez & Bolland, 1979). Figure 4Open in figure viewerPowerPoint Tetranychus evansi male: empodium II. (A–D) variation of the empodium of leg II in the species. Two differents types may be encountered on the same specimen (from Gotoh et al., 2009). (4A) also corresponds to male empodium I. (4C) also corresponds to female empodium I. Male Body 400–470 μm long and 220–290 μm wide. From yellowish pale orange to orange; legs pale orange. Tibia I with 9 tactile setae and four sensory setae. Tarsus I with 2 proximal sensory setae and 4 tactile setae just proximal to first pair of duplex setae. Empodium I with mediodorsal spur and pair of proximoventral spurs (Fig. 4a). Empodium II with mediodorsal spur as empodium I and proximoventral appendages varying from spurs as empodium I, long claws and hairs (Fig. 4). Aedeagus as Fig. 5. Figure 5Open in figure viewerPowerPoint Tetranychus spp, males aedeagus. (A–D) variation of the shape of the aedeagus of T. evansi; (A) from Mauritius, (B–D) from Japan; (E) T. marianae; (F) T. piercei; (G) T. urticae. [(A) from Baker & Pritchard, 1960; (B–D) from Ehara and Ohashi, 2002; (E) from Pritchard and Baker 1955; (F) from Guttierez and Bolland, 1979 (G) T. urticae, from Pritchard and Baker 1955)]. Identification requires the slide preparation of both males and females specimens when possible in correct position (see Appendix 1). Genus identification can be made using Bolland et al., 1998. Specific identification is made by the examination of the female, confirming the attribution to the desertorum group, ensuring that the main characters of this group have been seen (diamond pattern, tarsus I aligned setae). Specific determination is completed by the lateral examination of the male aedeagus which should exactly match the drawings. The use of Figs 1-5 drawings and the match of all the above characters allow the separation of T. evansi from closely related species. Tetranychus evansi is separated from the other species belonging to the desertorum group encountered in Europe by the shape of the aedeagus, as represented in Fig. 6. Figure 6Open in figure viewerPowerPoint Aedeagus of the desertorum group species found in Europe. (A) Tetranychus ludeni; (B) Tetranychus desertorum; (C) Tetranychus evansi. Reporting and documentation Guidance on reporting and documentation is given in EPPO Standard PM7/77 (1) Documentation and reporting on a diagnosis. Performance criteria When performance criteria are available, these are provided with the description of the test. Validation data are also available in the EPPO Database on Diagnostic Expertise (http://dc.eppo.int), and it is recommended to consult this database as additional information may be available there (e.g. more detailed information on analytical specificity, full validation reports, etc.). Further information Further information on this organism can be obtained from: A. Migeon, CBGP – INRA, Campus International de Baillarguet, Avenue du Campus Agropolis, CS 30016, 34988 MONTFERRIER-sur-LEZ Cedex, France. alain.migeon@supagro.inra.fr Feedback on this diagnostic protocol If you have any feedback concerning this Diagnostic Protocol, or any of the tests included, or if you can provide additional validation data for tests included in this protocol that you wish to share please contact diagnostics@eppo.int. Protocol revision An annual review process is in place to identify the need for revision of diagnostic protocols. Protocols identified as needing revision are marked as such on the EPPO website. When errata and corrigenda are in press, this will also be marked on the website. Acknowledgements This protocol was originally drafted by: A Migeon, CBGP – INRA, Campus International de Baillarguet, Avenue du Campus Agropolis, CS 30016, 34988 Montferrier-sur-Lez Cedex, France. Appendix 1: Preparation of specimens Specific identification requires examination of slide mounted adult males and females. Hoyer medium (see Table 1) is traditionally used but it contains toxic chloralhydrate. Use of clearing and mounting directly for non-permanent slides in lactic acid is convenient for a rapid identification. Clearing should last 24 h at room temperature or few hours at approximately 40°C. Use a cavity ground in slide as described by Gutierrez (1985a). The cavity is made with a small tungsten carbide grindstone mounted on a drill and should be about 3 mm diameter. The use of such slides allows the orientation of the specimen in any direction inside the cavity, by sliding the cover glass back and forth. Females are examined dorso-ventrally and males laterally to observe the shape of the aedeagus. Sealing with Euparal allows the preparation to be kept for 2 or 3 years. Table 1. Hoyer's medium Distilled H20 50 mL Arabic gum (acacia) 30 g Choral hydrate 200 g Glycerin 16 mL Dissolve Arabic gum completely in the distilled H2O. Then, and only then, completely dissolve in Choral hydrate, then add glycerin and mix well. Medium may be diluted when needed with small amounts of distilled H2O. Before using Hoyer's medium, let it stand undisturbed for several days in order to clarify. Store mixture at 4°C. References Baker EW & Pritchard AE (1960) The tetranychoid mites of Africa. Hilgardia 29, 455– 574. Baker EW & Tuttle DM (1994) A Guide to the Spider Mites (Tetranychidae) of the United States, pp. 347. Indira Publishing House, West Bloomfield (US). Bolland HR, Gutierrez J & Flechtmann CHW (1998) World Catalogue of the Spider Mite Family (Acari: Tetranychidae), pp. 392. Brill Academic Publishers, Leiden (NL). Boubou A, Migeon A, Roderick G & Navajas M (2011) Recent emergence and worldwide spread of the red tomato spider mite, Tetranychus evansi: genetic variation and multiple cryptic invasions. Biological Invasions 13, 81– 92. Duverney C & Ngueye-Ndiaye A (2005) Essais préliminaires pour limiter les dégâts de Tetranychidae sur les cultures maraîchères dans le Sine-Saloum (Sénégal). Deuxième colloque international sur les acariens des cultures, Montpellier (FR) (in French). Ferragut F & Escudero LA (2002) La araña roja del tomate Tetranychus evansi (Acari, Tetranychidae) en España: distribuciòn, biologìa y control. Phytoma España 132, 111– 113 (in Spanish). Fiaboe KKM, Fonseca RL, De Moraes GJ, Ogol CKPO & Knapp M (2006) Identification of priority areas in South America for exploration of natural enemies for classical biological control of Tetranychus evansi (Acari: Tetranychidae) in Africa. Biological Control 38, 373– 379. Flechtmann CHW & Knihinicki DK (2002) New species and new record of Tetranychus Dufour from Australia, with a key to the major groups in this genus based on females (Acari: Prostigmata: Tetranychidae). Australian Journal of Entomology 41, 118– 127. Gotoh T, Araki R, Boubou A, Migeon A, Ferragut F & Navajas M (2009) Evidence of co-specificity between Tetranychus evansi and Tetranychus takafujii (Acari: Prostigmata, Tetranychidae): comments on taxonoùic and agricultural aspects. International Journal of Acarology 35, 485– 501. Gutierrez J (1985a) Mounting techniques. In Spider Mites their Biology, Natural Enemies and Control, Vol. 1A, (eds W Helle & MW Sabelis), pp. 351– 353. Elsevier Science Publisher, Amsterdam (NL). Gutierrez J (1985b) Systematics. In Spider Mites their Biology, Natural Enemies and Control, Vol. 1A, (eds W Helle & MW Sabelis), pp. 75– 90. Elsevier Science Publisher, Amsterdam (NL). Jeppson LR, Keifer HH & Baker EW (1975) Mites Injurious to Economic Plants, pp. xxiv + 614. University of California Press, Berkeley (US). Knapp M, Saunyama IGM, Sarr I & de MG (2003a) Tetranychus evansi in Africa - Status, Distribution, Damage and Control Options. Deutcher Tropentag International Research on Food Security, Natural Resource Management and Rural Development, Göttingen (DE). Meyer MKPS (1987) African Tetranychidae (Acari: Prostigmata) - with Reference to the World Genera, Entomology Memoir, Department of Agriculture and Water Supply, Republic of South Africa 69, 1– 175. Migeon A & Dorkeld F (2006-2010) Spider Mites Web: a comprehensive database for the Tetranychidae. http://www1.montpellier.inra.fr/CBGP/spmweb/index.php [accessed 18 February 2011]. Migeon A, Ferragut F, Escudero-Colomar L, Fiaboe K, Knapp M, de Moraes G et al. (2009) Modelling the potential distribution of the invasive tomato red spider mite, Tetranychus evansi (Acari: Tetranychidae). Experimental and Applied Acarology 48, 199– 212. Moutia LA (1958) Contribution to the study of some phytophagous Acarina and their predators in Mauritius. Bulletin of Entomological Research 49, 59– 75. Rossi Simons NH (1961) Lista de las especies de Tetranychidae (Acari) de la Republica Argentina. Idia 163, 9– 13 (in Spanish). Silva P (1954) Um novo ácaro nocivo ao tomateiro na Bahia. Boletim do Instituto Biologica da Bahia 1, 1– 20 (in Portuguese). Wene GP (1956) Tetranychus marianae McG., a new pest of tomatoes. Journal of Economic Entomology 49, 712. Citing Literature Volume43, Issue3December 2013Pages 425-430 FiguresReferencesRelatedInformation