Tetranychus mexicanus is a polyphagous spider mite recorded on more than 100 plant species (EPPO, 2023; Migeon & Dorkeld, 2026). However, the host status of many plants remains uncertain (EPPO, 2023). Among cultivated plants, Citrus spp. are major hosts, but the mite also occurs on cultivated plants, such as papaya (Carica papaya), passion fruit (Passiflora spp.), Annona spp., palms and various ornamental species (EPPO, 2023; Migeon & Dorkeld, 2026). The list below includes hosts and likely hosts, that is plant species on which T. mexicanus can complete its life cycle, or is reported as a pest, or for which field evidence (e.g. multiple life stages or sufficient numbers of individuals) indicates the presence of a breeding population (EPPO, 2023). On many other plants, these factors could not be verified, and these plants are therefore considered uncertain hosts (EPPO, 2023). Uncertain hosts include cultivated plants, such as Annona reticulata, Averrhoa carambola, Codiaeum, Hovenia dulcis and Rosa. A complete list is available in EPPO (2023) and EPPO Global Database.

Tetranychus mexicanus is restricted to the Americas, with confirmed records from the southern United States in North America, to Uruguay and northern Argentina in South America (EPPO, 2023; Migeon & Dorkeld, 2026). There is no evidence of establishment outside this region: reports from China are unsubstantiated, and a single incursion in the Netherlands was successfully eradicated in 2019 (EPPO, 2023; Migeon & Dorkeld, 2026; NVWA, 2019).

Tetranychus mexicanus develops through five stages: egg, larva, protonymph, deutonymph and adult. The three active immature stages (larva, protonymph and deutonymph) are each followed by a brief quiescent, non-feeding phase before moulting to the next stage. These resting phases are termed protochrysalid (before the protonymph), deutochrysalid (before the deutonymph) and teliochrysalid (before the adult) (EPPO, 2023; Sousa et al., 2010). This mite reproduces both sexually and via arrhenotokous parthenogenesis, in which, respectively, fertilized eggs develop into females and unfertilized eggs into males (Paschoal, 1968). As a result, a single female can establish a new population: upon colonizing a host plant, she may initially produce male offspring and subsequently mate with them, enabling the production of female progeny and rapid population growth. Eggs are laid on leaf surfaces or within protective silk webbing produced by the mites. The life cycle is generally completed on the leaves of the host, on which immature stages and adults feed. Colonies are generally formed on the lower leaf surface. On Citrus, the mite is also occasionally found on twigs and fruits (Bobot et al., 2011; EPPO, 2023; Flechtmann & Baker, 1975). At a local scale, T. mexicanus, as with other mites in the family Tetranychidae, disperses mainly by crawling between adjacent plant tissues and nearby plants, and through passive aerial dispersal (Kennedy & Smitley, 1985). This is particularly important in nurseries, greenhouses and orchards where host plants are closely spaced. Once established, the mite can rapidly colonize neighbouring plants because all life stages occur on leaves, and populations may build up quickly under suitable conditions.

To date, T. mexicanus has been found only in tropical and subtropical climates. Its upper and lower temperature thresholds are not known, nor its adaptability to a wider range of temperatures. The biology of T. mexicanus has been studied in the laboratory on leaves of Citrus aurantifolia (Paschoal, 1968), Annona muricata, Annona squamosa and Annona coriacea (Sousa et al., 2010), Bactris gasipaes (Stein & Daólio, 2012) and Carica papaya and Passiflora edulis (Barroncas et al., 2022). Under favourable conditions (around 25°C), development from egg to adult generally takes 10–13 days, although it extended to 18–20 days onC. aurantifolia under less controlled temperature conditions (19–25°C). The duration of immature stages also varies among hosts; for example, egg development ranges from about 2–4 days onA. coriacea to 6.5 days onC. aurantifolia. Similarly, total immature development is faster on A. muricata and A. coriacea, and slower on B. gasipaes. Reproductive parameters also show substantial variation. Fecundity ranges from as few as 9 eggs per female on B. gasipaes to over 100 eggs per female on C. papaya. The oviposition period is longest on Annona spp. (approximately 17–23 days) and shorter onB. gasipaes (about 12 days). Adult longevity likewise differs among hosts, with females generally living between 17 and 25 days. Generation time ranges from approximately 16–24 days and sex ratio is strongly female-biased. Consistent with other tetranychid mites,T. mexicanus exhibits a high reproductive potential.

Symptoms

Symptoms resemble those caused by other spider mites (Moraes et al., 2024; Moraes & Flechtmann, 2008; Ochoa et al., 1994). These appear on both leaf surfaces but are more evident on the upper side. At low infestation levels, small white spots may occur and are easily overlooked. Typical symptoms include chlorosis that can progress to necrosis, along with leaf deformation (EPPO, 2023). Detailed descriptions for some hosts are summarized in the EPPO PRA (EPPO, 2023). On Citrus, infestations cause chlorosis, leaf curling and webbing on the lower surface, with chlorotic areas above that may become necrotic; severe cases can lead to defoliation, especially under stress (Moraes & Flechtmann, 2008; Ochoa et al., 1994; Silva et al., 2017). Additional effects on Citrus include slight fruit discoloration (EPPO, 2023). Across other hosts, symptoms generally involve chlorosis, necrosis and leaf deformation. Examples include yellowing, curling and defoliation in A. muricata (Silva et al., 2019); chlorosis and leaf death in C. papaya (Santos et al., 2018); and leaf discoloration or spotting in Paullinia cupana (Vasconcelos et al., 2022). Yellow patches are also reported in ornamentals (Feres et al., 2009), while Cocos nucifera shows characteristic leaf bronzing (Teodoro et al., 2015).

Morphology

The morphology of T. mexicanus varies across developmental stages but follows the general pattern of tetranychid mites.

Egg: Spherical, about 0.15 mm in diameter; initially transparent, turning dark yellow prior to hatching (Paschoal,1968; Stein & Daólio, 2012).

Larva: Light yellow, with three pairs of legs, and measuring 0.2–0.3 mm in length. As development proceeds, dark spots appear in the podosoma (part of body bearing legs) (Paschoal,1968; Stein & Daólio, 2012).

Protonymph and deutonymph: Possess four pairs of legs, and measuring approximately 0.3–0.45 mm in length, with deutonymphs larger than protonymphs. Colour is variable (light to dark green, yellow-green or red), and dark spots may extend to the opisthosoma (rear portion of the body) (Paschoal,1968; Stein & Daólio, 2012).

Adult: Also with four pairs of legs. Females are larger (around 0.5 mm in length), while males are smaller (about 0.25 mm in length) and have a tapered posterior body (Paschoal,1968). Colour is highly variable, ranging from yellowish or green to brown, orange or red, even within the same host plant. Adults typically show dark dorsal spots (Andrade et al., 2007; Stein & Daólio, 2012).

Detection and inspection methods

Detection of T. mexicanus is challenging because it shares symptoms and visual characteristics with other spider mites. It is also common to find multiple spider mite species on the same plant, further complicating identification. Feeding damage is non-specific, and similar symptoms and colouration in other spider mites make field identification unreliable. Colonies of phytophagous mites may be visible to the naked eye, but at low infestation levels, individuals and eggs are easily missed. For reliable detection, especially at early stages, a hand lens (≥20× magnification) or a microscope should be used (EPPO, 2023). Colonies are typically located on the underside of leaves, although they may sometimes also occur on the upper surface, and occasionally on twigs or on fruits. Like other spider mites, T. mexicanus produces webbing that can contain all life stages (Ochoa et al., 1994; Teodoro et al., 2015). It is reported to produce more abundant webbing than other common citrus spider mites, such as Panonychus citri and Eutetranychus banksi (EPPO, 2023). Additional detection clues include a thin whitish layer of exuviae and dust debris adhering to the webbing, particularly on the underside of leaves (Teodoro et al., 2015).

Identification of T. mexicanus is difficult due to its close resemblance to other Tetranychus species, and colour is unreliable as a distinguishing characteristic because it varies widely within the genus and even within the species itself. Accurate identification is based on morphological characters and requires specimens to be mounted on microscope slides. Species-level determination relies mainly on the shape of the male aedeagus (Gutierrez, 1985). Female characters, such as pregenital striae and tarsal chaetotaxy, can assist the identification (Santos et al., 2018). In practice, specimens are identified using descriptions and taxonomic keys (McGregor, 1950; Pritchard & Baker, 1955; Seeman & Beard, 2011). Molecular methods are not well established (EPPO, 2023).

The main pathway for long-distance movement is international trade in infested plant material (EPPO, 2023). The most important pathway is host plants for planting with leaves (including plants with roots and cuttings). This pathway is considered the highest risk because mites are primarily associated with foliage of living host plants. A wide range of woody and perennial hosts contribute to this pathway, including frequently traded ornamentals, such as Beaucarnea recurvata (with a documented interception in the Netherlands) (NVWA, 2019), as well as multiple fruit tree and shrub genera (EPPO, 2023). Citrus and related Rutaceae genera also form part of this host spectrum and are relevant due to their susceptibility. All life stages may be present on foliage, and populations may survive and even reproduce during transport and storage under favourable conditions. A second relevant pathway, associated with a low likelihood of entry, is above-ground fresh cut plant parts of hosts (cut flowers, cut foliage and cut branches, as well as leaf vegetables). These commodities may carry mites on leaves or tender stems. Survival may be possible under cool transport conditions typical of the flower and foliage trade, but transfer is unlikely because these commodities are short-lived and not intended for planting. A third, low risk pathway is host fruit, only if green parts are associated. Although T. mexicanus has been occasionally associated with fruit of Citrus sinensis, such occurrences are rare and transfer to a host would be difficult. Entry on fruit without green parts was therefore considered unlikely (EPPO, 2023). Other very unlikely pathways include for example non-host plant material or host wood, which are unsuitable for mite survival.

Economic impact

Control

According to EPPO (2023), control of T. mexicanus relies on preventive and curative measures, as no single method is fully effective. Chemical control is the main strategy during outbreaks, with acaricides generally effective; however, repeated applications are often required due to frequent reinfestation (Andrade et al., 2007). As observed in other Tetranychus species, the mite's short life cycle and high fecundity may favour the development of resistance, and reduced pesticide availability in the EU could further limit control options (APRD, 2026; EPPO, 2023; Van Leeuwen et al., 2010). Biological control may contribute to the regulation of pest populations, as natural enemies often keep infestations at low levels. In its native range, a variety of natural enemies contribute to the biological control of spider mites, such as T. mexicanus, particularly predatory mites (McMurtry et al., 2013; Moraes et al., 2024), and similar groups are also present in the EPPO region, including in citrus crops (Abad-Moyano et al., 2009). Commercial predatory mites, such as Amblyseius swirskii, Phytoseiulus persimilis and Neoseiulus californicus, are available in the EPPO region, although their effectiveness against T. mexicanus remains uncertain (EPPO, 2023).

Phytosanitary risk

The phytosanitary risk of T. mexicanus for the EPPO region is primarily driven by its strong association with live host plants for planting, especially those bearing foliage, which represent the main pathway for entry. The pest is highly polyphagous, but particular concern is linked to woody perennials and ornamental hosts and several economically important fruit producing genera, including Citrus, Prunus, Pyrus, Vitis, Fragaria, Annona and Persea. These hosts can be traded as plants for planting and can support all life stages, enabling survival and potential population development during transport. The risk of establishment is strongly influenced by climate and production systems. Outdoors, T. mexicanus is most likely to establish in the southern part of the EPPO region with mild winters, such as coastal areas of the Mediterranean and the Black Sea, and southern Portugal, in areas where host plants are widely present year-round (EPPO, 2023). In these regions, establishment in protected conditions (greenhouses and nurseries) is expected to be equally likely as outdoors, particularly where continuous host availability exists. Protected cultivation systems producing citrus seedlings and ornamentals year-round may therefore act as persistent reservoirs and amplification sites. In contrast, in more temperate parts of the EPPO region, outdoor establishment is unlikely due to winter conditions, and greenhouse establishment would only occur where hosts are continuously present. Increasing drought frequency—associated with climate change—may promote population outbreaks (Litskas et al., 2019). The potential impact in the EPPO PRA area is uncertain but could increase under favourable conditions. On cultivated crops, citrus is the main concern: damage is reported on C. sinensis in Brazil, although there is uncertainty about its potential impact on citrus varieties grown in the EPPO region. For ornamental plants, the potential impact of T. mexicanus may be higher. Its detection on B. recurvata in the Netherlands indicates the ability to infest previously unreported hosts, and heavy infestations in greenhouses suggest it could become a significant pest of ornamentals (EPPO, 2023; NVWA, 2019).

Phytosanitary measures are recommended for plants for planting with leaves (except tissue cultures) of hosts (EPPO, 2023). The following options were identified: pest free area; pest-free production site or pest free place of production established under physical isolation according to EPPO Standard PM 5/8 (EPPO, 2016); pest free place of production/pest free production site with inspection of the consignment prior to export (no T. mexicanus observed); or post-entry quarantine for 4 weeks in conditions suitable for the development of the mite (at 25°C or more) (in the framework of a bilateral agreement). Inspection of the consignment prior to export with no T. mexicanus observed, followed by treatment(s) of the consignment which are effective against all life stages of T. mexicanus is also an option, which is considered to provide a lower protection.

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This datasheet was prepared in 2026 by Adenir Vieira Teodoro, Embrapa Tabuleiros Costeiros, Brazil. His valuable contribution is gratefully acknowledged.

The EPPO pest risk analysis on Tetranychus mexicanus was prepared in 2022 by an EPPO expert working group composed of W. Dermauw (ILVO, BE), M.T. Martínez Ferrer (Institute of Agrifood Research and Technology, ES), M. Navajas (INRAE, FR), A.V. Teodoro (Embrapa, BR) and D.J. van der Gaag (NVWA, NL).

This datasheet was first published in the EPPO Bulletin in 2026.  It is maintained in an electronic format in the EPPO Global Database. The sections on 'Identity', ‘Hosts’, and 'Geographical distribution' are automatically updated from the database. For other sections, the date of last revision is indicated on the right.