Tetranychus evansi Baker & Pritchard, 1960

Toroitich, Faith J., Ueckermann, Edward A., Theron, Pieter D. & Knapp, Markus, 2009, The tetranychid mites (Acari: Tetranychidae) of Kenya and a redescription of the species Peltanobia erasmusi Meyer (Acari: Tetranychidae) based on males, Zootaxa 2176, pp. 33-47 : 43

Tetranychus evansi Baker & Pritchard, 1960

Male of T. evansi has a slender aedeagal shaft that curves dorsad; axis of knob forms a strong angle with shaft axis; knob very small but bearing a small anterior projection and a relatively longer acute and somewhat deflexed posterior projection ( Figure 5 A). Female tarsus I with proximal pair of duplex setae more or less in a line with tactile setae and empodium I with a minute mediodorsal spur.

Specimens examined: Many specimens have been examined all collected on solanaceous plants from Kenya which include Lycopersicon esculentum from Kajiado, Migori, Suba, Nakuru, Machakos, Kwale, Makueni and Taita districts; Solanum incanum from Mwea; Solanum nigrum from Baringo, Kiambu and Taita; Solanum melongena from Kibwezi and Machakos and Solanum tuberosum from Sagana, Nyeri district.

Remarks: This species was first described from Mauritius on Lycopersicon esculentum ( Baker and Pritchard, 1960) and is considered an invasive in Africa and parts of Europe. It has a worldwide occurrence but is not considered as a serious pest in the country of origin which is believed to be Brazil. However, in introduced places, it posses a threat to commercial production of solanaceous crops especially in greenhouse conditions and warmer climates. This species has been reported on a wide variety of host plants but it shows preference for plants from the family solanaceae . An earlier report of this species was on Lycopersicon esculentum (Solanaceae) from Kirinyaga district ( Knapp et al., 2003) and is currently the most important pest in tomato production in Kenya being wide spread in the major tomato growing areas. Biological control of this pest using the phytoseiid mite Phytoseiulus longipes Evans are underway and preliminary results in Kenya show high levels of control in the laboratory. However, field efficacy of the predator is not known since field releases have not been carried out. This species is brick-red to dark orange in colour when observed in the field. It produces dense webbing compared to the other species of the same genus in the field. In severe cases, the web produced covers the entire plant. Some pesticides registered for the control of spider mite are still effective in their control except dimethoate which is ineffective against T. evansi (Toroitich, unpublished data).

Figures

FIGURE 5. Tetranychus sp. aedegi modified after Meyer, 1974 (with permission).: (A) T. evansi aedeagus; (B) T. lombardiini aedeagus; (C) T. ludeni aedeagus; (D) T. neocaledonicus aedeagus; (E) T. urticae aedeagus.