First report of a predatory mite in association with Floracarus perrepae (Acariformes: Eriophyidae), a biological control agent for Old World climbing fern in Florida

Floracarus perrepae Knihinicki & Boczek (Acariformes: Eriophyidae) is a small gall-forming mite that was introduced to Florida as a biological control agent for the invasive weed Old World climbing fern, Lygodium microphyllum (Cav.) R.Br. (Lygodiaceae). This vine forms dense mats that can smother native vegetation, alter fire dynamics, and change habitat structure (Pemberton and Ferriter 1998). Following host-range testing, the U.S. Department of Agriculture, Animal and Plant Health Inspection Service (USDA APHIS) issued a release permit for the mite (Permit No.: 76027, December 2006). The USDA Invasive Plant Research Laboratory in Fort Lauderdale, Florida began releasing F. perrepae in 2008 as a biological control agent to assist in managing L. microphyllum infestations. Following the initial release and establishment, a mass-rearing and release program started in 2014, and since its inception, over 49 million mites have been released. Self-sustaining populations are successfully established at many locations throughout the invaded range (L. Crees personal observation; Lake et al. 2014). Adventive populations of F. perrepae can have a significant negative effect on L. microphyllum infestations (David and Lake 2020). Additionally, F. perrepae readily colonizes regrowth from herbicide treated L. microphyllum, making it a beneficial component of an integrated pest management program (David et al. 2021).

Recently, predatory mites have been observed while dissecting F. perrepae induced galls on L. microphyllum in the mass-rearing colony (Figure 1). Dissection of developed galls revealed that many lacked live mites with only adult mite cuticles remaining. Further investigation led to the discovery of a previously unidentified mite, much larger than F. perrepae, observed feeding on both adult and immature F. perrepae in the mass-rearing colony. Following these observations, surveys of wild F. perrepae populations were conducted and the same predatory mites appear to be present in wild populations.

Figure 1:

Amblyseius tamatavensis specimens from a Floracarus perrepae mass-rearing colony. Photo credit: Greg Wheeler.

Molecular analysis was conducted to identify the single predatory mite available at the time. We used an innovative technique developed previously to sequence single F. perrepae mites. This mite, collected from the mass-rearing colony, was dropped into 3 µL of GenomiPhi V2 buffer (Illustra GenomiPhi V2 DNA Amplification Kit, Marlborough, MA, USA), then the manufacturer’s instructions were followed at 1/3 volumes throughout (3 µL reaction buffer and 0.3 μL enzyme mix). The final product was diluted 1/10 with molecular-grade water and 1 μL of the diluent used in a 50 μL PCR reaction using Terra polymerase (Takara Bio, San Jose, California, USA) for 35 cycles at an annealing temperature of 50 °C. The forward primer used was 5′-AGAGGAAGTAAAAGTCGTAACAAG-3′ (Navajas et al. 1999). The reverse primer, designated mite_ITS1_R1Short (5′-GCTGCGTTCTTCATCGAT-3′), was designed from an alignment of representative Amblyseiinae. Several bands appeared when the PCR was visualized in a 1.5 % agarose gel, so the band appearing at about 400 bp was excised and then cleaned using the Zymoclean Gel DNA Recovery Kit (Zymo Research, Tustin, California, USA). The same primers were then used for Sanger Sequencing (McLab, South San Francisco, California, USA), resulting in a 363 bp sequence. The Basic Local Alignment Search Tool (BLAST) hosted at the National Center for Biotechnology Information (NCBI) was used for identification, resulting in a 100 % match with four existing records of the predatory mite Amblyseius tamatavensis Blommers (Acari: Phytoseiidae), accessions MG242085– MG242088. The predatory mite sample sequenced here has been submitted to NCBI and given the accession number SUB12630949. Döker et al. (2018) first reported specimens in the United States, collected in southern Florida from Laportea aestuans (L.) Chew (Urticaceae) and Solanum americanum Mill. (Solanaceae) in association with the banded-wing whitefly Trialeurodes abutiloneus (Haldeman) (Hemiptera: Aleyrodidae). Predatory mites in the family Phytoseiidae (Acari: Mesostigmata) have been documented feeding on soft-bodied insects like whiteflies and thrips but also on plant-feeding mites, as in this study.

Field surveys thus far also have found at least two additional mite species feeding on F. perrepae along with a single observation of a syrphid fly larva just outside the outermost roll of a gall. A life history study conducted in Australia prior to F. perrepae releases in Florida found six species of predatory mites, four of which were common (Ozman and Goolsby 2005). Predatory mites have been found in Lygodium galls on both the east and west coasts of Florida, suggesting a cosmopolitan distribution of predatory mites throughout the south Florida range of F. perrepae.

In Florida, galling on wild plants fluctuates throughout the year, with peak mite populations in the fall and spring (David et al. 2019; L. Crees, personal observation). These fluctuations in populations may be attributed to climatic factors that influence mite biology. Muthuraj and Jesudasan (2011) looked specifically at this fluctuation in the galling of L. microphyllum by F. perrepae in India and found that climatic factors significantly affect galling on wild plants in their native range, though it seems to be the culmination of multiple climatic effects instead of a single factor. How predatory mites and other predators of F. perrepae may contribute to this oscillating population pattern is an important consideration moving forward with other mites as biological control agents, as Smith et al. (2010) discussed. Additionally, a study aimed at exploring the fauna of L. microphyllum galls in the wild has been initiated to see if other species of mites may also be associated with F. perrepae.