Eutetranychus africanus (Tucker, 1926)

NavesK, Pedro, AguiarK, António Franquinho, Santos, Márcia, NóbregaK, Filomena, VarelaK, Ana Rita, Silva, Maria José, MigeonK, Alain, NaviaK, Denise & AugerK, Philippe, 2023, Two new alien Eutetranychus mites (Prostigmata, Tetranychidae) for Madeira Island, Portugal, Acarologia 63 (4), pp. 1154-1162 : 1157-1159

Eutetranychus africanus (Tucker, 1926)

The African red mite is reported from tropical and subtropical countries of the Afrotropical, Australasian and Oriental regions, and also in Iran and Egypt in the Palearctic region (Migeon and Dorkeld 2023). Damage to citrus and papaya has been reported in Africa (e.g. Kiptoo et al. 2022) and Asia (e.g. Ho et al. 2015).

Records: in Madeira, E. africanus was collected in four locations and four host plants ( Table 1). Mites were found mainly on the upper surface of the leaves, particularly near the mid-rib, and feeding damage was observed ( Figure 3 ).

Distinctive characters: females of this species are separated of other species of the banksi - group (16 species, see Kamran et al. 2018) by having coxa II with 2 setae, setae f 1 members equally spaced or slightly more widely spaced than setae e 1 members, dorsal striation between members of setae d 1 and e 1 forming a “V-pattern”, dorsocentral setae c 1, d 1 and e 1 inserted on obvious/prominent tubercles, 6 setae on tibiae II and III, 2 or 3 setae on genu III, 2 setae on genua II and IV ( Figure 4 ).

The molecular analysis confirmed the morphological identification, with a positive identification consisting of a BLAST hit with 100% identity of an alignment length of 999 nucleotides with a reference database sequence, belonging to E. africanus (accession number AB926232)

from Japan ( Matsuda et al. 2014). The novel sequences obtained in this study were deposited in GenBank under the accession numbers OQ312050 and OQ411006. As misidentification of E. africanus as E. orientalis has occurred repeatedly (e.g., Ehara and Gotoh 2007), despite the two species being easily separated using the coxa II setal count (2 setae present in E. africanus vs. 1 seta in E. orientalis ), our integrative approach, comparing both morphological and molecular characters to validated references, emphasizes its value in obtaining reliable identification of these species.

Species Host Coordinates Location (Parish) Altitude (m a.s.l.) Date of collection Eutetranychus africanus Citrus medica 32.6617°N - 16.9806°W Câmara de Lobos 233 17 May 2022 Eutetranychus africanus 1 Carica papaya 32.6795°N - 17.0744°W Ribeira Brava 117 31 May 2022 Eutetranychus africanus Vitis vinifera 32.6599°N - 16.9747°W Câmara de Lobos 196 12 Oct. 2022 Eutetranychus africanus 2 Ricinus communis 32.6573°N - 16.9003°W Funchal 28 13 Oct. 2022 Eutetranychus banksi 1 Citrus x auratium 32.6548°N - 16.8331°W Santa Cruz 261 07 Sept. 2020 Eutetranychus banksi 1 Plumeria rubra 32.6435°N - 16.8370°W Santa Cruz 86 30 Aug. 2022 Eutetranychus banksi Ricinus communis 32.6731°N - 16.8101°W Santa Cruz 225 13 Oct. 2022 Eutetranychus banksi Ricinus communis 32.6527°N - 16.8179°W Caniço 76 13 Oct. 2022 Eutetranychus banksi 1 Phaseolus vulgaris 32.6589°N - 16.9112°W Funchal 139 16 May 2023 Eutetranychus banksi 1 Citrus reticulata 32.7244°N - 17.1793°W Calheta 165 30 June 2023 Eutetranychus banksi 1 Citrus limon 32.6934°N - 17.1096°W Ponta do Sol 338 10 July 2023

Note: new species for Madeira Island and second record for the west Palearctic region; new host record on Citrus medica .

There is no information on how the two alien Eutetranychus arrived in Madeira or how long they have been present, but the movement or trade of mite-infested plant material is the most likely hypothesis to explain their introduction. The climate of southern Madeira can certainly provide suitable climatic conditions for their persistence, considering the mean annual temperature of 18 °C ( Mora and Vieira 2020).

Although E. africanus is mainly found in regions with tropical or sub-tropical climates ( Figure 1 ), its presence in northern Iran suggests the ability to survive cold winters, and therefore this species may represent an additional challenge for citrus orchards of the Mediterranean basin. Precautionary measures should be applied to contain the populations in Madeira and prevent future disseminations of this alien mite, considering the damages reported on citrus, papaya, and on other crops worldwide. We also recommend that surveys should be conducted in continental Europe to check the presence of E. africanus . It is possible that this species occurs in mixed infestation with other Eutetranychus species and has been unnoticed until now.

Figures

Figure 1 World distribution map ofEutetranychus africanusandEutetranychus banksi. For each species, country level (data derived from Migeon and Dorkeld, 2023) and geo–localized records are indicated.

Figure 3 Feeding damage byEutetranychus africanuson Citrus medicaleaf, Madeira Island.

Figure 4 Eutetranychus africanusfemale: A – dorsal opisthosoma with: setaef 1 in normal position, striation forming a ”V-pattern” between members of setaed1 ande1; B – first three pairs of dorsocentral setae (c1, d1 ande1) inserted on obvious tubercles; C – two setae present on coxae I and II; D – 6 setae on tibia III; E–F – 6 setae on tibia II: 3 dorsal (E) and 3 ventral (F); G – two setae on genu II; H – two setae on genu IV. Scale bars A=50μm, B–H=20μm.