Theobroma cacao, a new host for Brevipalpus yothersi (Acari: Tenuipalpidae) in Peru

Brevipalpus yothersi Baker (Acari: Tenuipalpidae) is reported for the first time on cocoa, Theobroma cacao L. (Malvaceae) in northwestern Peru. Mites were collected from organic cocoa smallholdings from September to December 2020 in eight localities (three Provinces) of the Piura Department. The highest mite population density was found on peduncle and epicarps of fruits of different phenological stages, and the lowest density on the leaves.


Introduction
Phytophagous mites of the genus Brevipalpus (Acari: Tenuipalpidae), commonly referred to as flat mites or false spider mites, are an emerging pest of agricultural and ornamental crops. Currently, about 318 species of the genus Brevipalpus have been described (Castro et al. 2020). Some Brevipalpus species are major plant pests because of their ability to transmit viruses to several economically important fruit trees, including citrus (Kitajima et al. 2010; FreitasAstúa et al. 2018, passion fruit , and coffee (Chagas et al. 2003). Brevipalpus yothersi Baker (Acari: Tenuipalpidae) is reported from 33 countries (Castro et al. 2020). It was first described by Baker (1949) from females and nymphs collected on privet, Ligustrum sp. (Oleaceae) collected by M. A. Yothers in Orlando, Florida, USA. Since then, it has been reported on various plant species around the world. Brevipalpus yothersi is widely distributed, and in South America it has been reported in Argentina, Brazil, Colombia, Ecuador, Venezuela  and Peru (present study). It is associated with the transmission of cytoplasmatic Cileviruses causing citrus leprosis (Roy et al. 2015). Ochoa et al. (1994) recorded Brevipalpus phoenicis s.l. (Geijskes) (Acari: Tenuipalpidae) on cocoa Theobroma cacao L. (Malvaceae) in Central America, and five Tenuipalpidae species have been reported on cocoa (Castro et al. 2020).
In Peru, cocoa beans are an important economic product, including several derivatives such as cocoa butter, cocoa paste, and cocoa powder, sold domestically and internationally (MINAGRI 2018). The Department of Piura has a total of 1,748 ha with 5,678 associated producers (APPCACAO 2020). There are no previous records of B. yothersi in Peru and not on cocoa either. This article reports T. cacao as a new host plant for B. yothersi in Peru. The finding of B. yothersi affecting cocoa is of considerable concern and it is essential to determine the potential pest status on this important crop. Our research objective was to determine the presence of the mite and the damage caused to cocoa trees in organic smallholding production and contribute to Integrated Pest Management programs' strategies.

Materials and methods
In this study, cocoa tree flat mites were collected in smallholdings under the organic production system from September to December 2020 (Table 1). The collection areas are of a tropical and subtropical desert climate and were surveyed during the spring season. Five cocoa trees were randomly selected at each locality and 25 leaves and five fruits of different phenological stage were collected randomly, packed in separate paper bags, and sent to the Entomology Laboratory, Facultad de Agronomía, Universidad Nacional de Piura, Perú. The mites were observed and counted under a stereomicroscope (ZEISS Stemi 508 with Aixocam ERc 5s digital camera) and mounted on slides in Hoyer's medium (Krantz and Walter 2009). The identification of the species was based on morphological identification using an Omax 40x 2500x phase contrast trinocular microscope with an OMAX S35180U318Mp camera, and taxonomic keys provided by Beard et al. (2015). Voucher specimens were deposited in the Acarology collection of the aforementioned institution.

Results and discussion
We report B. yothersi for the first time in Peru and also its first report on cocoa, T. cacao. Brevipalpus yothersi was found in all eight localities surveyed. The following morphological characteristics were used to identify B. yothersi: prodorsum centrally rugose, lateral sections with strong areolae (usually longitudinally elongate), large sublateral cells and becoming broadly wrinkled to smooth anterior to setae v2 ( Figure 1A). The opisthosoma with strong "V" shaped folds from setae e1 to h1 ( Figure 1B) and with six pairs of lateral setae. The ventral plate is uniformly verrucose with small rounded warts. The genital plate is verrucosereticulate with large cells ( Figure 1C). Spermathecal apparatus has a long, narrow duct which fuses with an oval vesicle that has a small distal stipe ( Figure 1D). Gnathosoma with a lanceolate dorsal seta on the femurogenu palp and leg II with two solenidia on the tarsus . Adult females are orangered, flat, oval in shape and were observed on leaves and fruits ( Figure  2B). The eggs are elliptical and bright reddishorange in color. The larvae are orangered in color. The nymphal stages are weak reddishorange color with green and hyaline spots.  Brevipalpus yothersi was observed and collected on the leaves, peduncle, and epicarps of fruits of different phenological stages. The mite's presence was noticed on mature fruits close to harvest. The symptoms associated with the lesions caused by these mites were more representative on fruits where population densities were higher (mean 10.3 mites/cm 2 ) compared to the populations found in leaves (mean 1.21 mites/leaf). The large number of adult and immature mites were located in the groove between the ridges of the epicarp of the fruit (Figure 2A). During the survey, brown spots were observed on the epicarp of fruits in the eight localities (Figure 2A and 2C). Some fruits had large areas of dark brown epicarp and abundant exuviae ( Figure 2D). Brevipalpus yothersi was observed in lignified areas on the epicarp resulting from damage caused by several species of Tuckerella (Acari: Tuckerellidae), taking advantage of the crevices for protection and to lay eggs.
There are few studies about the mite diversity in cocoa. Several species of fungivorous Tarsonemidae mites were reported from cocoa trees in Brazil and Costa Rica (Ochoa et al. 1995; Ochoa and OConnor 1998; Rezende et al. 2015; Sousa et al. 2018. Six species of Eriophyoid mites have been reported associated with Theobroma spp. Aceria reyesi (Nuzzaci) (Acari: Eriophyidae) is the only mite species known to cause serious damage and its importance as a cocoa pest is recognized in some Central and South American countries (Carvalho et al. 2018). The mite attacks the terminal buds of cocoa branches, causing atrophy, premature leaf drop, and shortening of the internodes (Doreste et al. 1975). Eleven species of phytophagous mites of the family Tetranychidae have been reported in association with Theobroma spp. (Migeon and Dorkeld 20062020). Flechtmann (1979) reported for the first time Tuckerella ornata (Tucker) (Acari: Tuckerellidae) on the woody stem and stem cracks of cocoa plants in Belém, State of Pará, Brazil. In Peru, three species of Tuckerella associated with cocoa have been observed (EscobarGarcia et al. 2021). In addition, in the location of Lalaquiz (Table 1), a population of Brevipalpus californicus s.l. (Banks) (Acari: Tenuipalpidae) was recently collected and its presence is being investigated. Furthermore, worldwide two Phytoseiidae species ) have been reported on cocoa.
The presence of B. yothersi in Peru is of concern as it is a vector of several plant viruses affecting economically important crops, such as citrus and passion fruit (FreitasAstúa et al. 2018). This species is the principal vector of Citrus leprosis virus (CiLV) (Roy et al. 2015; Ferreira et al. 2020) and as such is considered a quarantine pest (Peña et al. 2015). Recently the first draft of the genome sequence of B. yothersi has been reported, which is also the first mite vector of the plant virus to be sequenced (Navia et al. 2019). This report emphasizes the importance of carrying out studies of biology, ecology, geographical distribution and economic impact on the production of cocoa by mites, as well as to determine the potential role of Brevipalpus species as a vector of diseases in cocoa trees.