Phytoseiid mites (Acari: Phytoseiidae) from Senegal.

This paper refers to the first report of mites of the family Phytoseiidae from Senegal. It is based mostly on a survey conducted in the Fatick (Sine Saloum) Region, in the interior, and the Dakar Region, at the coast, in search of predators associated with the tomato red spider mite, Tetranychus evansi Baker and Pritchard. The latter has been recently introduced to Senegal, where it is causing considerable damage to solanaceous plants. Phytoseiids have been widely studied in other countries for the biological control of phytophagous mites. Seven species were found in this survey. Measurements of the species collected are provided. Neoseiulus californicus (McGregor) was only found in 2010. This could represent a new introduction into the country; it is reported for the second time in northern sub-Saharan Africa. This species and Amblyseius swirskii Athias-Henriot were often associated with T. evansi and Tetranychus urticae Koch, but their possible impact on those pests was not evaluated.


INTRODUCTION
In the last 15 years, the tomato red spider mite, Tetranychus evansi Baker & Pritchard (Acari: Tetranychidae), has spread to several countries in Africa, Asia and Europe (Migeon & Dorkeld 2007). It has also been recently reported for the first time in Senegal (Duverney et al. 2005). Even before the introduction of this species, mites of the families Tarsonemidae and Tetranychidae were already considered problems on solanaceous plants in Senegal (Diouf, 1994). The introduction of T. evansi has turned those problems more severe, mainly on tomato (Solanum lycopersicum L.), eggplant (Solanum melongena L.) and "jaxatu" (Solanum aethiopicum L.).
Mites of the family Phytoseiidae have been widely studied for the biological control of phytophagous mites. Virtually nothing is known about these mites in Senegal; no species was reported from this country in the world phytoseiid catalog (Moraes et al., 2004). Diouf (1994) conceived a prospective role of phytoseiid mites on Solanum aethiopicum L. and other plants of the same family in Senegal, for the control of phytophagous mites. Phytoseiid mites have been studied in other countries in the context of their possible use as control agents of T. evansi (Furtado et al., 2006(Furtado et al., , 2007. The inventory of the faunistic composition in a given region is one of the first steps in an effort to establish a biological control program against a pest species. A survey was recently initiated, to determine the natural enemies associated with T. evansi in two regions of Senegal (Duverney et al., 2005). The objective of this paper is to report the phytoseiid mites collected in that survey.

MATERIAL AND METHODS
The survey was conducted at the following localities: Malika and University Cheikh Anta Diop (in the coastal Dakar Region), Batamar, KBD Center, Senghor and Sokone [in the inland, Foundiougne Department of Sine-Saloum (= Fatick) Region] between 2005 and 2010.
All specimens were collected by Niokhor Kade. Because of the preference of T. evansi for Solanaceae (Moraes et al., 1987), most effort was dedicated in the survey to examine plants of that family, although nearby plants of other families were also examined. Sampled plants were checked under stereomicroscope and mites found were mounted in Hoyer's medium for identification.
Mites were measured under an optical microscope (at 400 or 1000 X) for comparisons with original descriptions and re-descriptions of phytoseiid species. When more than two specimens were examined, measurement of each structure is indicated by the mean followed (in parentheses) by the respective range, in micrometers. The classification system used is that of Chant & McMurtry (2007). The setal terminology of Rowell et al. (1978) and Chant & Yoshida-Shaul (1991) were used for dorsal and ventral idiosomal setae, respectively. Except where otherwise specified, world distribution of each species is based on Moraes et al. (2004).
Remarks -Most measurements of the specimens collected are similar to those reported by Zannou et al. (2007) for specimens from sub-Saharan Africa. However, the lengths of s4, Z4, Z5 and leg macrosetae are close to the corresponding upper limits of the ranges shown by those authors for those setae.
World distribution -This species has been reported from tropical and subtropical regions of the Americas, sub-Saharan Africa, Canary Island, Asia and Oceania.
Remarks -Measurements of the specimens collected are very similar to those reported by Zannou et al. (2007) for specimens of sub-Saharan Africa and Israel.
Specimens collected -23 females and 6 males on Passiflora foetida L., in June 2009, and 56 females and 17 males, on Solanum aethiopicum L., in May 2009, at Malika. In both cases, the predator was commonly associated with T. evansi and Tetranychus urticae Koch.
World distribution -This species has been reported from the Mediterranean region, southwest Asia and northern and sub-Saharan Africa.
Remarks -Measurements of the specimens collected are similar to what was reported in redescriptions of the species based on specimens from California (Schuster & Pritchard, 1963) and Peru (Guanilo et al., 2008), except for the anterolateral dorsal shield setae and Z5, about 10 % shorter in the specimens collected.
Specimens collected -More than 50 specimens on Solanum aethiopicum L. and S. melongena L., infested by T. evansi and T. urticae, at Malika, between March and July 2010.
World distribution -This species has been reported from subtropical to temperate areas in the Americas, Europe, Asia and northern Africa. A few years ago (Pringle & Heunis, 2006) it was introduced to South Africa for the control of mite pests in apple orchards; thus, our finding is the second record of this species in sub-Saharan Africa (Zannou et al., 2006).
Remarks -Measurements of the specimens collected are similar to those given by Moraes et al. (2007) for specimens from sub-Saharan Africa, including the holotype. The presence of a macroseta on genu II and not on genu III, observed in the specimens collected and in the specimens examined by Moraes et al. (2007) is not common for other phytoseiid mites. Usually, the presence of a macroseta on a given leg implies its presence on subsequent legs.
Specimens collected -28 females and 9 males on Centaurea perrotettii DC., Chrosophora senegalensis Vis. and Urena lobata L, at KBD, in November 2009. World distribution -This species has been reported almost only from sub-Saharan Africa; the exception refers to a single report from India (Gupta, 1981).
Remarks -Measurements of the specimens collected are similar to those reported by Ueckermann et al. (2007) for specimens from sub-Saharan Africa, including the holotype; the length of the macroseta of basitarsus IV of the specimens collected is close to the lower extreme of the range given by those authors. The length of the calyx of the spermatheca is similar to that of the holotype and to the average given by Ueckermann et al (2007) for other specimens.
World distribution -This species has been reported almost only from sub-Saharan Africa; the exception refers to a single report from the Island of La Réunion, in the Indian Ocean (Quilici et al., 2000).

DISCUSSION
Despite the effort dedicated to the search for predatory mites in this survey, the diversity was relatively small. Paraphytoseius horrifer and Phytoseius amba were by far the most abundant and frequent species collected. While the former was found only in the Fatick Region (in the drier interior), the latter was found in both Fatick and Dakar Region (in the more humid coastal side).
Amblyseius herbicolus and A. swirskii were only found in Dakar Region. The latter is by far more abundant than the former. Although found in both Regions, E. nyalensis is most abundant and frequent in Fatick.
It is noteworthy that N. californicus was only collected in 2010, often in high numbers in association with Tetranychus species, and only in Dakar Region. Given its absence in the samples collected in the previous years, it seems that this species may represent a recent introduction to Dakar. This species was never found in sub-Saharan Africa in the extensive survey reported by Zannou et al. (2006). The common association of this species and of A. swirskii with T. evansi does not imply that they were having any impact on that pest. No study has been published so far on the effect of A. swirskii on T. evansi. However, studies conducted by different authors on N. californicus as predator of T. evansi have not shown promising results, as summarized by Furtado et al. (2007).