First record of two insects preying on the red tomato spider mite Tetranychus evansi (Acari: Tetranychidae) in Latakia governorate, Syria

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.


Introduction
The red tomato spider mite Tetranychus evansi Baker & Pritchard (Acari: Tetranychidae), has emerged as a new threat to solanaceous crops worldwide (Navajas et al. 2013). It is native to South America (Gutierrez andEtienne 1986; Boubou et al. 2011), but has largely expanded its geographical distribution, and now is present in 45 countries, including nearly all Mediterranean countries (Migeon and Dorkeld 2020). In Syria, this invasive mite has been recorded since 2011 in Latakia governorate, a Mediterranean coastal area (Zriki et al. 2014).
Classical biological control of invasive species by introducing exotic natural enemies is often advocated (Thomas and Reid 2007). However, extensive efforts should be dedicated for exploiting indigenous and/or endemic natural enemies and developing effective biocontrol agents to limit unwanted effects of classical biological control under international exchange rules (Hajek et al. 2016). In the case of T. evansi, few studies have been done to identify its endemic natural enemies in the invaded areas. In this paper, we recorded for the first time in Latakia governorate two predaceous insects in T. evansi colonies collected from wild and cultivated solanaceous plants in 2019.

Materials and methods
Leaves of black night shade, Solanum nigrum L. and tomato, S. lycopersicum L. (Solanales: Solanaceae) infested with T. evansi were randomly collected during autumn 2019 from 12 sites in Latakia governorate (Table 1). In each site, thirty leaves were placed in plastic bags, transported to the laboratory and examined under a stereomicroscope (Micros, Ladybird MZ1240, Austria).
Predatory insect specimens of Coccinellidae (Coleoptera) and Cecidomyiidae (Diptera) were observed in the colonies of T. evansi and identified using the identification keys of Kapur (1948) and Gagné (1995), respectively. To identify the coccinellid predators, male genetalia were extracted and slidemounted in glycerin on a glass slide for examination. For the identification of the cecidomyiid predatory species, leaves carrying mature larvae or cocoons were kept in plastic containers until the emergence of adults. All emerging adults were preserved in 70% ethyl alcohol for further identification. For microscopic examination, some of the ethanolpreserved specimens were cleared and mounted on slides in Hoyer's medium.

Results and discussion
Two species of predatory insects were identified from the colonies of T. evansi.

The ladybird beetle, Stethorus gilvifrons (Mulsant, 1850)(Coleoptera: Coccinellidae)
All life stages of S. gilvifrons were found in association with T. evansi colonies on tomato and black nightshade in half of the collected samples (Table 1). Both adults and larvae were observed preying on all developmental stages of T. evansi (Fig. 1). This is the first record of T. evansi as a prey of S. gilvifrons anywhere in the world. This predator is widely distributed in the Middle East and Southern Europe and has been reported to be an effective biocontrol agent of several spider mite species (Biddinger et al. 2009; Perumalsamy et al. 2010. In Syria, S. gilvifrons has been recorded in association with many tetranychid species in several habitats and was considered an effective predator of the red spider mite, T. urticae and the citrus red mite Panonychus citri (McGregor) (Aboufakhr hammad 2008; Mofleh 2010; Barbar et al. 2016. Many Stethorus species were found associated with T. evansi on solanaceous plants in native and invaded areas ( Table 2). Among these species, the tropical coccinellid, S. tridens Gordon was the only species evaluated under laboratory conditions and considered as a promising agent for the control of T. evansi (Fiaboe et al. 2007b; Britto et al. 2009).  The gall midge Feltiella acarisuga (Vallot, 1827) (Diptera: Cecidomyiidae) Feltiella acarisuga larvae of all instars and pupae were found on leaves infested with T. evansi in all collected samples (Table 1). Larvae of this predator have been observed preying on different developmental stages of T. evansi (Fig. 2). This species was found together with S. gilvifrons on the leaf samples of tomato and black nightshade (Table 1). Feltiella acarisuga is a cosmopolitan predator that is commercially used as a biocontrol agent against tetranychid mites (GanahaKikumura et al. 2012, Gagné andJaschhof 2017) and has been found in association with T. evansi in Spain and Japan (Table 2). Other Feltiella species were reported in association with T. evansi from different parts of the world (Table 2). In Syria, the occurrence of F. acarisuga was reported by Mofleh (2010) in association with T. urticae on various plants, including Solanaceae, from different localities of the Syrian coastal region. However, she did not provide any reliable information about the identification of the cecidomyiid. In addition, the voucher specimens are not available anywhere. In the present study, we confirmed the presence of F. acarisuga and reported T. evansi as a new prey to this species in Syria.

Conclusion
The two predatory insects, S. gilvifrons and F. acarisuga, appear to be promising biocontrol agents against T. evansi because they were found in association with all its life stages. As these two predators are naturally occurring in cultivated (S. lycopersicum) and uncultivated (S. nigrum) areas along the Syrian coast, further studies are clearly needed to evaluate their potential to regulate T. evansi populations.