Mite species (Acari) on blackberry cultivars in organic and conventional farms in Florida and Georgia, USA

This study was carried out to determine mite species on blackberry plants (Rubus spp. (Rosaceae)) in Florida and Georgia, USA, and differences in mite species between organic and conventional blackberry plantings in the area sampled. Surveys were conducted in organic and conventional commercial blackberry plantings from June to October 2016. Leaf samples were collected monthly from nine different blackberry cultivars including ‘Arapaho’, ‘Choctaw’, ‘Freedom’, ‘Kiowa’, ‘Natchez’, ‘Navaho’, ‘Osage’, ‘Ouachita’, and Von. Approximately 20 leaves per blackberry plant were taken. Twenty mite species (a total of 152 mite specimens) belonging to 7 families including Phytoseiidae (9 species), Ascidae (1), Cheyletidae (1), Erythraeidae (1), Stigmaeidae (1), Tetranychidae (4) and Tarsonemidae (3) were identified during the study. It was found that the abundance of predatory mites collected in organic farms was over 2-fold higher (105) than in conventional farms (47), which may be related to pesticide use on these commercial farms. Future surveys should provide a list of predatory species, which may hold potential for biological control of economically important pest mites.


Introduction
Blackberries (Rubus spp. (Rosaceae)) are a major small fruit crop that is grown throughout Europe and the United States (Strik 2007). Mexico is the leading producer of blackberries worldwide. In the US, the crop is valued at 50 million USD (USDANASS 2016) with 90% of its production in the northwest region (Oregon). Production is expanding in the southern United States (Arkansas to Florida) and several new cultivars are being developed that do not require the heat units for satisfactory production that is required of traditional cultivars.
Several mite species have been found in association with blackberry plants (Vincent et al. 2010) and most of these mites are agricultural pests that are known to cause economic damage. The broad mite, Polyphagotarsonemus latus (Banks) is one of two species in the family Tarsonemidae that cause extensive damage to crop plants (Liburd et al. 2020). Polyphagotarsonemus latus has been found in association with leafcurling symptoms on primocanefruiting blackberry (Rubus L. subgenus Rubus Watson) in Arkansas (Vincent et al. 2010), which negatively affect plant growth and development. Davies et al. (2001) examined microhabitats and aggregation patterns of the phytophagous mite, Acalitus essigi (Hassan) (Trombidiformes: Eriophyidae), on Rubus fruticosus L. (Rosaceae). They found that A. essigi was a refugee inhabiting species that resided in the buds and leaf axils on primocanes and fructocanes. Scott et al. (2008) collected the same species of eriophyid mites from the fruits of three species of the weedy blackberry (R. anglo candicans A. Newton, R. laudatus A. Berger and R. ulmifolius Schott) in southwest Australia. This was the first record for this species in Western Australia and these plants appear to be new host records for A. essigi. Similarly, Cetin et al. (2010) recorded A. essigi as a new pest in blackberry plantings in the Marmara region of Turkey in 2009. Marchetti and Ferla (2011) determined the diversity and population fluctuation of mites on blackberry (R. fruticosus) in Rio Grande do Sul, Brazil. A total of 26 mite species belonging to 12 families were found. Most of the mites were phytophagous species belonging to the families Diptilomiopidae (80.9%) and Tetranychidae (13.9%). The most common families of predaceous mites were Stigmaeidae (2.1%) and Phytoseiidae (0.4%). Recently, Trinidad et al. (2019) evaluated the occurrence of phytophagous and predatory mites in different blackberry genotypes in the municipality of Pelotas, RS, Brazil. They recorded a total of 12 mite species belonging to the families Tetranychidae, Diptilomiopidae, Eriophyidae, Tarsonemidae, Tenuipalpidae, Stigmaeidae, Tydeidae, Phytoseiidae. The families Tydeidae, Diptilomiopidae, Tetranychidae, and Eriophyidae showed a higher representability.
Ozsisli and Cobanoglu (2019)  In a recent study, Akyazi and Liburd (2019) assessed the effectiveness of a commercially available predator, Neoseiulus californicus (McGregor) to reduce T. urticae populations in a commercial blackberry planting and recommended that an assessment of local phytoseiids and other predators should be considered before further releases of N. californicus are considered.
To our knowledge a survey of mite fauna associated with blackberries have not been conducted in Florida and Georgia despite an expanding blackberry industry in the region. This study was carried out to determine phytophagous and predatory mite species on nine commercially available blackberry cultivars in Florida and Georgia, USA in 2016.

Sampled Areas
The survey was conducted in selected organic and conventional commercial blackberry farms in Florida and Georgia, USA ( Figure 1). Geographical coordinates were recorded using a GPS mobile device.

Sampling Method
The survey was conducted from June to October 2016. Leaf samples were collected monthly. The number of sampled plants per site was determined according to the total number of the plants in each planting (Table 2). On each sampling date, leaves were taken from different parts of the bush canopy, i.e. lower, middle, and upper canopy. Approximately 20 leaves per blackberry plant were collected. The samples were placed in paper bags and then later in Ziplock plastic bags, labeled and transferred to the University of Florida, Small Fruit and Vegetable IPM (UFSFVIPM) laboratory.

Extraction, preparation, and identification of mite specimens
The mites were collected with a 0 or 00 paint brush under a stereomicroscope LEICA M205 C (Leica Microsystems Inc., Buffalo Grove, Illinois, USA) directly from the leaves. In this way, all mites were separated into families before examination using 40 x to 160 x magnification.

Results and Discussion
During the surveys, a total of 20 mite species belonging to 7 families were identified (Table 3) as follows: nine species of Phytoseiidae, four Tetranychidae, three Tarsonemidae, one for each of Ascidae, Stigmaeidae, Cheyletidae and Erythraeidae.

Typhlodromips dentilis (De Leon)
Amblyseius dentilis AthiasHenriot Amblyseius (Typhlodromopsis) dentilis Muma Comments -Typhlodromips dentilis has been found on many different types of plants worldwide (Demite et al. 2020). In Florida, it was recorded for the first time on Rhus copallina in Miami, Florida, USA and subsequently in various localities in Florida (Denmark and Evans 2011; Muma 1964ab; Muma and Denmark 1970. During the present study, T. dentilis was found together with populations of P. latus, T. schoenei, E. carpini and T. confusus.
Rebek (2017)  Comments -Tarsonemus bilobatus has been reported on many plant species in Central America (Costa Rica), Europe (Byelorussia, Hungary, Italy, Poland, Ukraine), Asia (China, India Japan, Korea,), Africa (Egypt) (Lin andZhang 2002; Zhang 2003) and South America (Brazil) (Lofego et al. 2005; Rezende et al. 2012. It was also collected from bacterial and fungal cultures, stored food products, litter and soil. It is primarily a fungivorus species (Zhang 2003 Comments -Tarsonemus confusus occurs on many types of plants in Canada, Byelorussia, Egypt, China, Ireland, Italy, Japan, Germany, Korea, Netherlands, Ukraine, Poland, Russia, Turkey (Lin and Zhang 2002), Hungary (Ripka et al. 2005) and Brazil (Lofego et al. 2005). It was also previously recorded from multiple states in the US on various plants including Rubus sp. (Lin and Zhang 2002 Comments -Eotetranychus carpini has been widely reported in Europe (Migeon et al. 2007; Malagnini et al., 2012) . It is also found in Mexico (Beer and Lang 1958) and USA (McGregor 1917). To date, it was reported from 30 countries in two major regions of Nearctic and Palearctic (Migeon and Dorkeld 2020). This species also exploits a wide range of host plants and have been reported on 54 host plants including Rubus idaeus (Migeon and Dorkeld 2020) and Rubus sp. (Bolland et al. 1998 Comments -Tetranychus schoenei is widely distributed over the eastern and southwestern United States. Previous distribution records included Georgia (Flechtmann and Hunter 1971). It is also found in Iran (Beyzavi et al. 2013). According to Migeon and Dorkeld (2020), to date, it was reported from 2 countries and on 52 host plants including Rubus allegheniensis, R. idaeus, R. occidentalis (Reeves 1963), Rubus sp. (Reeves 1963; Seeman andBeard 2011).

Tetranychus urticae Koch
Fifty species names have been synonymized with T. urticae in spider Mites Web (Migeon and Dorkeld 2020

Conclusion
In conclusion, the total number of mites collected in organic farms (105) was over 2fold higher than in conventional farms (47). Moreover, while all of the twenty mite species identified during the study could be collected from organic farms, just nine could be obtained from conventional farms. The total number of beneficial mites collected in the organic farm was 57. In contrast, 23 beneficial mites were collected from conventional farms (Table 3). These results may be related to pesticide use on the conventional farms and are similar to that previously reported for mites (Incekulak and Ecevit 2002; Yanar and Ecevit 2008; Akyazı et al. 2016; Fathipour and Maleknia 2016; Soysal and Akyazı 2018.

Mite Species Mite Numbers
just one mite was collected from Navaho (Table 4). We hypothesize that differences in mite numbers and diversity may be caused by different phytochemical components, morphological and histological leaf structure of blackberry cultivars as stated by Camporese and Duso (1996), Krips et al. (1999), Kretier et al. (2002), Kabicek (2008), Khan et al. (2008) and Ali et al. (2015) for different plants. It should be noted that a single factor is not responsible for the abundance and diversity of mites but a combination of factors. Since the effect of cultivars on the mite population is timeconsuming, such results can only be observed in the long term. As far as we know, no previous research has investigated the effect of blackberry cultivars on the mite population. And, future investigations are necessary to validate the kinds of conclusions that can be drawn from this study.