Plant biosecurity is increasingly challenged by emerging crop pests. The spider mite Tetranychus evansi has recently emerged as a new threat to solanaceous crops in Africa and the Mediterranean basin, with invasions characterized by a high reproductive output and an ability to withstand a wide range of temperatures. Mitochondrial (868 bp of COI) and nuclear (1,137 bp of ITS) loci were analyzed in T. evansi samples spanning the current geographical distribution to study the earliest stages of the invasive process. The two sets of markers separate the samples into two main clades that are only present together in South America and Southern Europe. The highest COI diversity was found in South America, consistent with the hypothesis of a South American origin of T. evansi. Among the invaded areas, the Mediterranean region displayed a high level of genetic diversity similar to that present in South America, that is likely the result of multiple colonization events. The invasions of Africa and Asia by T. evansi are characterized by a low genetic variation associated with distinct introductions. Genetic data demonstrate two different patterns of invasions: (1) populations in the Mediterranean basin that are a result of multiple cryptic introductions and (2) emerging invasions of Africa and Asia, each likely the result of propagules from one or limited sources. The recent invasions of T. evansi illustrate not only the importance of human activities in the spread of agricultural pests, but also the limits of international quarantine procedures, particularly for cryptic invasions.

Using a combination of the cytochrome oxidase subunit I gene (COI) and internal transcribed spacer (ITS) sequence information, cross-breeding, and morphological criteria, the taxonomic status of Tetranychus takafujii was reassessed. Described from Japan and very close to Tetranychus evansi, only the male empodium II separated the two species. Six T. evansi samples collected in Brazil, France, Kenya, Spain (including the Canary Islands), Taiwan, and two samples from Japan previously species-identified as T. takafujii, were examined. DNA sequences consistently divide the samples into two groups: group I held the mites from Brazil and France and group II contained the remaining samples of T. evansi together with the two mites collected in Japan. Likewise, crossbreeding experiments detected the same two groups that were reproductively partially incompatible. However, the Japanese samples were completely compatible with the rest of the group II T. evansi samples. The empodium II shape failed to distinguish consistently between the T. evansi and T. takafujii samples, but rather highlighted its variability, questioning its utility for separating these taxa. Congruent results support the co-specificity of the two taxa. It is concluded that T. takafuji is a junior synonym of T. evansi.

The spider mite Tetranychus evansi is an emerging pest of solanaceous crops worldwide. Like many other emerging pests, its small size, confusing taxonomy, complex history of associations with humans, and propensity to start new populations from small inocula, make the study of its invasion biology difficult. Here, we use recent developments in Approximate Bayesian Computation (ABC) and variation in multi-locus genetic markers to reconstruct the complex historical demography of this cryptic invasive pest. By distinguishing among multiple pathways and timing of introductions, we find evidence for the “bridgehead effect”, in which one invasion serves as source for subsequent invasions. Tetranychus evansi populations in Europe and Africa resulted from at least three independent introductions from South America and involved mites from two distinct sources in Brazil, corresponding to highly divergent mitochondrial DNA lineages. Mites from southwest Brazil (BR-SW) colonized the African continent, and from there Europe through two pathways in a “bridgehead” type pattern. One pathway resulted in a widespread invasion, not only to Europe, but also to other regions in Africa, southern Europe and eastern Asia. The second pathway involved the mixture with a second introduction from BR-SW leading to an admixed population in southern Spain. Admixture was also detected between invasive populations in Portugal. A third introduction from the Brazilian Atlantic region resulted in only a limited invasion in Europe. This study illustrates that ABC methods can provide insights into, and distinguish among, complex invasion scenarios. These processes are critical not only in understanding the biology of invasions, but also in refining management strategies for invasive species. For example, while reported observations of the mite and outbreaks in the invaded areas were largely consistent with estimates of geographical expansion from the ABC approach, historical observations failed to recognize the complex pathways involved and the corresponding effects on genetic diversity.

The red tomato spider mite Tetranychus evansi is an important invasive pest of solanaceous plants worldwide. It has been recorded in Syria since 2011 in Latakia governorate, a Mediterranean coastal region. During survey conducted in 2019, the ladybird beetle, Stethorus gilvifrons (Mulsant) (Coleoptera: Coccinellidae) and the acarivorous gall midge, Feltiella acarisuga (Vallot) (Diptera: Cecidomyiidae) were identified in association with T. evansi colonies on tomato and black nightshade from 12 sites in Latakia. Larvae of F. acarisuga, and larvae and adults of S. gilvifrons, were observed preying on all developmental stages of T. evansi. This is the first record of T. evansi as a prey of S. gilvifrons. A literature review of Stethorus and Feltiella species previously reported in association with T. evansi on solanaceous plants is also provided.

Phytoseiid mites have been considered the most promising predators for the control of pest mites and small insects. Their use in solanaceous crops for the biological control of major mite pests represents an important challenge and requires continued research. This study aimed at investigating the phytoseiid species and their associated phytophagous mites on eggplant (Solanum melongena), tomato (Solanum lycopersicum) and black nightshade (Solanum nigrum) in the Syrian coastal region between 2018 and 2020, at 40 sites. A total of 12 species of the three subfamilies (Amblyseiinae Muma, Phytoseiinae Berlese, and Typhlodrominae Scheuten) were collected, with Amblysiinae being the most represented. Among them, Amblyseius andersoni (Chant) is a new record for the Syrian fauna. Phytoseiulus persimilis Athias-Henriot was the most abundant (223 specimens; 47.3%) and frequent (found in 22 out of 40 sites) species collected on all plant species surveyed and the only common phytoseiid species in greenhouses. The second most abundant species was Neoseiulus californicus (McGregor) (83 specimens: 17.6%), while the second most frequent was Phytoseius finitimus Ribaga (8 sites). Species found in this study should be considered in future research on phytoseiid mites as biological control agents of pests of tomato and eggplant cultivated in greenhouses and open fields in this region.

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The tomato red spider mite, Tetranychus evansi Baker and Pritchard, has emerged as a destructive invasive pest of solanaceous crops worldwide. It was first recorded in Syria in 2011, in Latakia governorate, in the coastal region. Successful management of T. evansi in a given region benefits from information about its distribution, host plants, and associated natural enemies. Therefore, we investigated, in 2019 and 2020, the status of T. evansi on solanaceous plants in the Syrian coastal region, an important producer of solanaceous crops. A total of 237 samples were collected at 187 sites in Latakia and Tartus governorates. Tetranychus evansi was found in 34 cultivated and wild solanaceous plant samples collected at 29 sites distributed across all districts in those governorates, and in a variety of landscapes and elevations, ranging from the coastal plains to high altitudes in the Syrian Coastal Mountain Range. It was collected from three solanaceous crops, namely tomato (Solanum lycopersicum L.), eggplant (Solanum melongena L.) and potato (Solanum tuberosum L.), as well as from two wild solanaceous plants: black nightshade (Solanum nigrum L.) and red nightshade (Solanum villosum Mill.). A total of 14 species of predatory insects and mites, and five species of phytophagous mites, were identified in association with T. evansi. Predatory insects were more frequent and abundant than predatory mites. The insect predator Feltiella acarisuga (Vallot) was the most common and abundant species among the predators, followed by Stethorus gilvifrons (Mulsant) and Scolothrips longicornis Priesner. The predatory mite Phytoseiulus persimilis Athias-Henriot was the most frequent and abundant species of associated predatory mites.