The family Tenuipalpidae is known as false spider mites or flat mites. It contains over 1,100 valid species belonging to 38 genera (Vacante 2015). Members of the genus Brevipalpus Donnadieu, 1875, one of the dominant genera in the family, are considered as the most economically important group of species among the flat mites (Childers et al. 2003; Salinas-Vargas et al. 2016). These mites cause direct damage by inserting their mouthparts into plant tissues and sucking sap. They also inject their toxic saliva into the plant during feeding (Childers & Rodrigues 2011). Furthermore, several of these mites transmit viruses to host plants (Mesa et al. 2009; Salinas-Vargas et al. 2016).

Brevipalpus yothersi (Baker, 1949) (Prostigmata: Tenuipalpidae) is one of the more important flat mites, causing economic damage to many crop plants (Novelli et al. 2016). It was recently suggested to be the vector for cytoplasmic leprosis viruses (citrus leprosis virus C, citrus leprosis virus C2, and Hibiscus green spot virus 2) (Roy et al. 2015).

Brevipalpus yothersi was synonymized with B. phoenicis by Pritchard & Baker (1952) but Beard et al. (2015a) raised it again to species level and gave an extensive account of its distribution and host plants. But, so far, there have been no records of B. yothersi on blueberries grown in Florida. This paper reports blueberry as a new host of B. yothersi from Florida. Additionally, measurements (range in μm) of the Florida specimens, information regarding collection details, habitats, hosts, damage, and world distribution are also presented in this paper.

Material and Method

SCANNING ELECTRON MICROSCOPY (SEM)

To prepare specimens for electron microscopy, the method of Çobanoğlu et al. (2011) was used. Briefly, the samples were fixed in 70% alcohol. After fixation, the samples were dehydrated in an alcohol series (70%, 80%, 90%, 100%, and 100%) for 30 m each. Dehydrated specimens were critical-point-dried, and mounted on SEM stubs. Mounted samples were coated with gold/palladium (20 nm). The specimens were examined with a scanning electron microscope (FEI Nova 430 w/EDS & CL, Nanoscale Research Facility, University of Florida, Gainesville, Florida, USA).

Fig. 1.

Brevipalpus yothersi on blueberry (abundance) leaf - adult (a), egg (b), larva (c), protonymph (d).

Results

Fig. 2.

Brevipalpus yothersi female - dorsal propodosoma (a), opisthosoma (b).

Fig. 3.

Brevipalpus yothersi female - dorsal view (a), ventral view (b).

Fig. 4.

Brevipalpus yothersi female - ventral view of propodosoma (a), the region between coxal fields of legs III and IV, and the bases of setae 3a and 4a, and the area between setae 3a and 4a, and the area posterior to the 4a setae (b).

Fig. 5.

Brevipalpus yothersi female - ventral view of anal and genital regions (a), spermatheca (b), dorsal seta on palp femorogenu (c), distal part of palpus (d).

LIGHT MICROSCOPY AND SEM ANALYSIS OF DIFFERENT STAGES OF BREVIPALPUS YOTHERSI

FEMALE (n = 5) (Figs . 2–6)

Dorsum: Central portions of prodorsum with strong areolae, usually longitudinally elongate, while the posterior cuticle of the sublateral prodorsum is reticulate with large cells and anterior to setae v2 with weak reticulation, becoming broadly wrinkled to smooth posterior to v2 (Fig. 2a). Opisthosoma with 6 pairs of lateral setae with setae f2 absent (Fig. 2b, 3a). Ornamentation between setae c1-c1 to d1-d1 smooth to weakly reticulate. Area between the setae d1-d1 and e1-e1 with weak reticulations and wrinkles. The strong V-shaped folds from setae e1-e1 to h1-h1 is one of the characteristics of B. yothersi, but much weaker towards h1 (Fig. 2b). Measurements of setae as follows: length between setae v2-h1 217 to 222; width between setae sc2-sc2 138 to 144, c3-c3 149 to 179. Dorsal setae lanceolate, barbed: v2 9 to 12, sc1 8 to 11, sc2 10 to 11, c1 6 to 8, c3 6 to 9, d1 6 to 7, d3 8 to 9, e1 7 to 9, e3 8 to 10, f3 9 to 11, h1 9 to 11, h2 8 to 10.

Fig. 6.

Distal part of tarsus II of Brevipalpus yothersi female.

Ventral: Base of coxal fields of legs I and II are finely verrucose (Fig. 4a). The region between coxal fields of legs III and IV and the bases of setae 3a and 4a is verrucose. Area posterior to the 4a setae is uniformly verrucose but between setae 3a and 4a is smooth to finely verrucose (Fig. 3b, 4b).

The ventral plates are uniformly verrucose, whereas the genital plate is verrucose-reticulate with large cells (Fig. 5a).

Spermathecal apparatus (Fig. 5b): The spermathecal duct is long, narrow and ending in vesicle. The spermathecal vesicle is oval-shaped with a thick distal stipe.

Palpus: Dorsal seta on palp femorogenu is barbed, narrow, setiform (Fig. 5c) and palp tibia with 2 setae and 1 omega (Fig. 5d).

Legs: B. yothersi has 2 solenidia (ω) on tarsus II (Fig. 6). Length of legs (base of coxae to tip of claws) as follows: leg I 149 to 179; leg II 156 to 173; leg III 140 to 150; leg IV 150 to 160.

MALE (n = 1) (Fig . 7a)

The adult males are more wedge-shaped than females. They have same ventral pattern as female.

DEUTONYMPH (n = 4)

Dorsum: Length between setae v2-h1 171 to 222; width between setae sc2-sc2 110 to 129, c3-c3 117 to 145. Dorsal setae: v2 5 to 6, sc1 5 to 12, sc2 9 to 14, c1 4 to 5, c3 4 to 8, d1 3 to 4, d3 4 to 6, e1 3 to 4, e3 3 to 6, f3 13 to 17, h1 10 to 16, h2 10 to 16.

Legs: Length of legs (base of coxae to tip of claws) as follows: leg I 104 to 127; leg II 96 to 108; leg III 85 to 88; leg IV 82 to 94.

PROTONYMPH (n = 2)

Dorsum: Length between setae v2-h1 146 to 173; width between setae sc2-sc2 104 to 110, c3-c3 107 to 122. Dorsal setae: v2 4, sc1 6 to 7, sc2 9 to 11, c1 3, c3 3 to 7, d1 2, d3 3, e1 3, e3 3, f3 11 to 13, h1 11 to 12, h2 10 to 12.

Fig. 7.

Ventral view of Brevipalpus yothersi male (a) and Brevipalpus yothersi larva (b).

Legs: Length of legs (base of coxae to tip of claws) as follows: leg I 83 to 85; leg II 71 to 72; leg III 62 to 64; leg IV 60 to 62.

LARVAE (n = 2) (Fig . 7b)

Dorsum: Body measurements: length between setae v2-h1 131 to 170; width between setae sc2-sc2 85 to 107, c3-c3 99 to 111. Dorsal setae: v2 3 to 4, sc1 5, sc2 9 to 10, c1 3, c3 3 to 4, d1 2, d3 4, e1 3, e3 4 to 5, f3 10 to 13, h1 9 to 12, h2 12 to 65.

Legs: Length of legs (base of coxae to tip of claws) as follows: leg I 83 to 85; leg II 71 to 72; leg III 62 to 64; leg IV 60 to 62.

HOST PLANTS AND DISTRIBUTION

Brevipalpus yothersi seems to have a cosmopolitan distribution and a very broad host range, with a strong association with Citrus spp. (Rutaceae) (Beard et al. 2015b). Because B. yothersi was considered to be B. phoenicis (Geijskes) since 1952, when it was synonymized with the latter (Pritchard & Baker 1952), its hosts and geographic distribution are given here based on material examined by Beard et al. (2015a) in Table 1.

Table 1.

Geographical distribution and host records of Brevipalpus yothersi (based on examined material by Beard et al. (2015a).

DAMAGE

Brevipalpus spp. are economically important plant-feeding mite species. These species damage plants directly by feeding on the epidermal cells of the stems, leaves, and fruits (Peña et al. 2015; Salinas-Vargas et al. 2016). They feed by inserting their chelicerae into the host plant tissue. During feeding, toxic saliva is injected into the cells. The sap is then mixed with saliva and sucked up by the mite. Brevipalpus spp. usually feed on twigs, leaves, and fruit (Childers et al. 2011). The symptoms associated with injury caused by these mites vary from necrotic brown spots on leaves, resinous leaf patches with opposing leaf, stem browning, gall formation, brownish patches on the fruit surface, corky ring-like bands around the fruit to defoliation and die back depending on the host plant species (Childers et al. 2003).

Brevipalpus mites also can act as vectors of viruses. Their role as vectors of citrus leprosis virus (CiLV) has greatly increased their worldwide importance as quarantine pests (Peña et al. 2015).

Fig. 8.

Blueberry leaves infested with Brevipalpus yothersi and the bacterial plant disease Xylella sp. (Bacteria: Xanthomonadales).

In this study, necrotic brown spots were observed together with the symptoms of Xylella sp. (Bacteria: Xanthomonadales) on blueberry leaves infested with B. yothersi (Fig. 8).

Recently, it has been shown that B. yothersi has a strong association with the citrus leprosis virus complex and it has been suggested to be a vector of the cytoplasmic leprosis viruses (Roy et al. 2015). These viruses induce localized necrotic or chlorotic lesions around the mitefeeding sites (Ramos-Gonzalez et al. 2016).

Remarks

Brevipalpus yothersi was originally described as a separate species in 1949 (Baker, 1949). It was later considered as a synonym of B. phoenicis together with B. papayensis in 1952 (Pritchard & Baker, 1952). However, B. yothersi differs from B. phoenicis in having a narrowly lanceolate dorsal seta on palp femorogenu (Fig. 5c) instead of broad as in B. phoenicis. The spermatheca vesicle is round without stipe or not developed in B. phoenicis, whereas the spermatheca vesicle is oval with a strong distal stipe in B. yothersi. Furthermore, the cuticle on the dorsal opisthosoma between setae e1-e1 to h1-h1 is without strong chevrons, usually with more or less transverse folds in B. phoenicis, whereas the cuticle on the dorsal opisthosoma between setae e1-e1 to h1-h1 is usually with strong chevrons (V-shaped folds), becoming much weaker towards h1-h1 (Beard et al. 2015a ). Brevipalpus yothersi differs from B. papayensis as shown in Table 2.

Brevipalpus yothersi is listed as B. phoenicis group species B (Beard et al. 2015b). However, it was raised to species level again. It was also confirmed that Brevipalpus amicus Chaudhri, B. recula Chaudhri, B. mcbridei Baker, and B. deleoni Pritchard and Baker are junior synonyms of B. yothersi (Beard et al. 2015a).

Discussion

The family Tenuipalpidae Berlese includes more than 1,100 species in 36 genera (Beard et al. 2015; Çobanoğlu et al. 2016). Brevipalpus Donnadieu, 1875 is the largest genus in the Tenuipalpidae (Welbourn et al. 2003) and includes more than 300 species worldwide.

Within the genus Brevipalpus, B. yothersi was not detected during previous surveys carried out in Florida, USA, on blueberry. In this study, during surveys carried out in 2016 in Florida, it was reported on southern highbush blueberry (Vaccinium corymbosum L. × V. darrowi Camp (Ericaceae)). Brevipalpus yothersi was initially described from specimens collected on privet (Ligustrum sp.: Oleaceae) in Orlando, Florida, USA (Baker 1949). It was subsequently synonymized with B. phoenicis by Pritchard & Baker (1952). The mite was recently resurrected and redescribed (Beard et al. 2015a; Novelli et al. 2016). According to Beard et al. (2015a), it was collected from Citrus sp. (Orlando), Juglans regia (Juglandaceae) (Orlando), Cocos nucifera (Arecaceae) (Fort Lauderdale), Maranta sp. (Marantaceae) (Bradenton), Petrea sp. (Verbenaceae) (Miami), Archontophoenix alexandrae (Arecaceae) (Gainesville), Citrus sp. (with leprosis) (Rutaceae) (Lake Alfred) in Florida.

Table 2.

Morphological characteristics used to separate Brevipalus yothersi and Brevipalpus papayensis (Sanchez-Velazquez et al. 2015).

Within the group of Brevipalpus species that transmit plant viruses, B. yothersi is the principal vector of viruses causing the cytoplasmic type of leprosis (Rodrigues & Childers 2013; Roy et al. 2015; Arena et al. 2016; Ramos-Gonzalez et al. 2016). Previously, it was thought that all leprosis viruses could be transmitted only by B. phoenicis, but recently, the species status of B. phoenicis has been revised, and 4 species previously considered as synonyms of B. phoenicis have been confirmed as separate species.

Blueberry necrotic ring blotch virus (BNRBV) was reported from Florida by Quito-Avila et al. (2013). It is closely related to the viral plant diseases citrus leprosis virus and Hibiscus green spot virus (HGSV), which are transmitted by Brevipalpus species (Robinson 2013). In the future, it also will be necessary to elucidate the potential role of B. yothersi as a vector of blueberry necrotic ring blotch virus.

Like viruses, other plant pathogens including bacteria also are transmitted or spread by mites from different families such as Tenuipalpidae, Acaridae, Eriophyidae, Siteroptidae, Tarsonemidae and Tetranychidae (Sarwar 2015). Unlike viruses, most bacterial diseases of plants do not require vectors. However, vectors contribute to the spread of some bacterial pathogens of plants (Purcell 2009). We observed that leaves heavily infested with B. yothersi also were infected with the bacterial plant disease Xylella sp. (Fig. 8). Thus, further study may be necessary to determine the role of B. yothersi in the development and spread of Xylella in Vaccinium spp.