Aceria fraxinivora ( Nalepa, 1909 )

Korda, M., Csóka, Gy., Szabó, Á. & Ripka, G., 2019, First occurrence and description of Aceria fraxiniflora (Felt, 1906) (Acariformes: Eriophyoidea) from Europe, Zootaxa 4568 (2), pp. 293-306 : 301-302

Aceria fraxinivora ( Nalepa, 1909)

( Figs 13–17 )

Eriophyes fraxinivorus Nalepa, 1909: 117 .

Phytoptus fraxini Karpelles, 1884: 52 , pl 1, Figs 9–11 . Preoccupied.

E. fraxinivorus— Nalepa, 1911: 241. pl. 4. Figs 10 a, b .

Aceria fraxinivora — Roivainen, 1951: 8; Farkas, 1966: 30 –31, Fig. 17 D ; Xue et al., 2009: 474, 477–480, Figs 7–9 .

Aceria fraxinivorus (Nal.) — Keifer, 1952 no figure

Redescription. FEMALE. Body pale yellow, vermiform, 241 (190–305, n = 7), 67 (60–69) wide, 70 (56–72) thick. Gnathosoma 28 (23–29), projecting obliquely downwards; chelicerae 23 (21–26), dorsal palp genual setae d 3 (3–4), unbranched, pedipalp coxal setae ep 3 (3–4). Prodorsal shield 39 (30–45), 44 (32–48) wide, subtriangular; with frontal lobe 2 (2–3); shield smooth or with two faint, incomplete admedian lines, diverging posteriorly, more widely separate on rear ¼; median line absent. Tubercles of scapular setae sc on rear shield margin, 23 (20–25) apart, diverging, scapular setae sc 34 (32–36), directed rearwards. Granules situated in lateral rows on epicoxal areas, i.e. laterally between shield margin and dorsal coxae of legs I and II.

Legs with all usual segments and setae present. Leg I 38 (35–40), femur 11 (10–12), basiventral femoral seta bv 11 (10–12), genu 5 (5–6), antaxial genual seta l’’ 28 (25–30), tibia 9 (9–10), paraxial tibial seta l’ located at ¼– 2 ⁄5 from dorsal base, 4 (4–5), very thin, tarsus 8 (8–10), unguinal tarsal setae u′ 4 (3–5), solenidion ω 9 (8–9), distally knobbed, slightly curved, empodium simple, bilaterally symmetrical, 7 (6–7), 4-rayed, each ray of three basal pairs with additional secondary branches.

Leg II 35 (33–38), femur 10 (9–10), basiventral femoral seta bv 10 (9–10), genu 5 (4–5), antaxial genual seta l’’ 8 (7–10) very thin, tibia 8 (7–8), tarsus 9 (8–9), unguinal tarsal setae u′ 3 (3–4), solenidion ω 9 (8–10), distally knobbed, slightly curved, empodium simple, bilaterally symmetrical, 8 (7–8), 4-rayed, each ray of three basal pairs with small subdivisions.

Coxigenital area with 5–6 microtuberculate semiannuli. Coxisternae I and II with several granules; anterior seta on coxisternum I, 1b 7 (6–10), tubercles setae 1b 11 (10–11) apart, proximal seta on coxisternum I, 1a 24 (20– 26), tubercles setae 1a 8 (8–9) apart, proximal seta on coxisternum II, 2a 37 (32–38), tubercles setae 2a 21 (19–24) apart. Subcapitular plate rounded. Prosternal apodeme 8 (8–9).

Opisthosoma with 63 (50–66) dorsal, 61 (59–66) microtuberculate ventral semiannuli. Microtubercles oval dorsally and rounded ventrally. Last 6–10 dorsal annuli with tiny microtubercles on rear annular margin. Last 4–5 ventral annuli with linear microtubercles. Opisthosomal seta c2 23 (20–25), on annulus 10 (9–10), 55 (50–60) apart; opisthosomal seta d 68 (58–71), on annulus 21 (20–21), 32 (30–36) apart; opisthosomal seta e 18 (15–23), on annulus 37 (34–38), 18 (16–24) apart; opisthosomal seta f 28 (26–29), on annulus 57 (55–61), or 5 (4–5) from the rear, 21 (20–24) apart. Opisthosomal seta h2 82 (78–94), very thin at apex, 10 (10–11) apart; opisthosomal seta h1 5 (5–6), 8 (7–8) apart. Anal lobes normal in size and shape.

Genital plate 19 (18–21), 23 (21–25) wide. Female genital coverflap with 10 (9–10) longitudinal ridges; coxisternal III setae 3a 15 (12–18) apart, 11 (10–13), very thin.

NYMPH. White, wormlike, 205–215 (n = 2), 65 thick. Gnathosoma 25–26. Prodorsal shield 31–33. Setae sc 25–26, pointing rear. Leg I 25–29, leg II 23–26. Opisthosoma with 52–56 dorsal, 47–54 ventral semiannuli. Dorsal and ventral semiannuli with minute microtubercles. Setae c 2 12–14, on annulus 8–10; setae d 40, on annulus 17– 20; setae e 10–11, on annulus 28–31; setae f 19–22, on annulus 43–50, or 4 from rear. Setae h2 66; setae h1 2; setae 3a 10–12.

Host plant. European ash, or Common ash, Fraxinus excelsior L. (fam. Oleaceae ). European ash is a native tree species to Hungary.

Relationship to the host. This mite caused distinct inflorescence and fruit deformation in the shape of a mass of globular sponge-like galls. The panicles swelled and distorted. The mite was found on the pubescent and lumpy samaras and remnants of panicles of the host ( Fig. 17 ).

Hungarian locality. Budapest ( Central Hungary), district II, Törökvész út, street trees, 195 m, elev .; 47°31’44.2” N, 19°00’15.1” E.

Material examined. The redescribed female circled with black ink among 5 females and one nymph on one slide, 3 April 2018, slide # 1439a; 6 females, 2 nymphs, one male, and one female and one male of Tegolophus califraxini (Keifer) , and one female of Aculus fraxini (Nalepa) on slide # 1439b, coll. G. Ripka. Other specimens were collected by G. Ripka, from fruit galls of Fraxinus angustifolia Vahl in Budapest second district, 21 May 2018, slide # 1442a, containing 7 females and 2 nymphs. Other specimens were collected by Mr. M. Korda, from fruit galls of Fraxinus ornus L. in Sopron (Gyȏr-Moson-Sopron county), 21 June 2018, slides ## 1444a, b containing 30 females and 2 nymphs, and 25 females and one nymph, resp. which are in the corresponding author’s collection and deposited in the National Food Chain Safety Office , Directorate of Plant Protection , Soil Conservation and Agri-environment, Department of Pest Management Development and Coordination, Budapest, Hungary .

Differential diagnosis. The morphometric differences are summarised in Table 1, but we especially draw attention to the length of setae sc: 17–25 in A. fraxiniflora , whereas it is 32–36 in A. fraxinivora . There is another marked difference in the length of seta h2, which is about twice as large in A. fraxinivora (78–94) as it is in A. fraxiniflora (25–40). We also note that the surface of the posterior dorsal opisthosomal and telosomal annuli differ, with the last 4–5 annuli almost smooth, with tiny or dot-like microtubercles in A. fraxiniflora , whereas 6–10 similar annuli are seen in A. fraxinivora ( Table 1; J.W. Amrine, pers. comm.). Additionally, A. fraxiniflora has some design on the prodorsal shield, e.g. two admedian lines and a shallow and V-shaped line mesally on the rear margin between the admedians, whereas the majority of the examined specimens of A. fraxinivora have none, but some others have extremely faint lines.

The relevant species causing leaf galls are easily separated from the inflorescence gall-formers. The most significant characteristics of the European leaf gall-inducer, Aceria fraxinicola (Nalepa) , are the almost smooth dorsal annuli, the 3-rayed empodium, the absent or slightly visible seta h1, and the length of seta 3a (20–28) ( Nalepa 1890; Farkas 1966). The North American leaf gall-inducer, Aceria fraxini (Garman) can be differentiated from the two inflorescence and fruit gall-inducer Aceria spp. by the smooth genital coverflap, the netlike pattern prodorsal shield design, the 3-rayed empodium, the length of setae 3a (18) and h1 (1) (compare them with Table 1) ( Baker et al. 1996).

Figures

FIGURE 17. Symptom of Aceria fraxinivora (Nal.) on fruits of European ash. (Photo: György Csóka)

FIGURES 13–16. SEM images of Aceria fraxinivora (Nal.). (13) probably a female, in dorsal view; (14) female, in lateral view; (15) female, in ventral view; (16) male, in lateral view. (Photos: László Szabó)

FIGURES 9–12. SEM images of Aceria fraxiniflora (Felt). (9) female, in lateral view; (10) probably a female, in dorsal view; (11) female, in ventrolateral view; (12) nymph, in ventrolateral view. (Photo: László Szabó)

FIGURES 7–8. Symptom of Aceria fraxiniflora (Felt) on fruits of green ash. (Photos: György Csóka)