Mites (subclass, Acari) constitute one of the most diverse and ecologically significant groups within the class Arachnida, occupying nearly every terrestrial habitat and playing crucial roles in ecosystems as decomposers, parasites, and plant associates [1]. Plant-inhabiting mites represent a particularly important ecological guild, comprising both phytophagous species that feed on plant tissues and may act as pests and predatory species that regulate populations of phytophagous mites and small arthropods [2][3]. The interactions between these two functional groups are central to maintaining ecological balance and crop productivity, especially in tropical agroecosystems [4].

Phytophagous mites, including those belonging to the families Tetranychidae (spider mites), Tenuipalpidae (flat mites), and Eriophyidae (gall and rust mites), are among the most damaging arthropod pests in agriculture. They attack various crops, including cassava, tomato, citrus, cotton, and coffee, and cause significant yield losses through direct feeding and indirect physiological effects on plants [5]. Members of Tetranychidae are particularly destructive owing to their rapid reproductive cycles and ability to develop resistance to acaricides [5]. In contrast, Phytoseiidae, a family of predatory mites within the order Mesostigmata, plays an essential role in natural and applied biological control by feeding on pest mites, thrips, and whiteflies [6]. Accordingly, their efficacy and specificity make them cornerstone organisms in integrated pest management programs worldwide. The most commercially significant Phytoseiidae species include Amblyseius swirskii, Phytoseiulus persimilis, Neoseiulus cucumeris, and Neoseiulus californicus. These predatory mites are primarily used to control spider mites (e.g. Tetranychus urticae), thrips, and whiteflies on vegetable, ornamental, and fruit crops. Moreover, their high reproductive rate, prey specificity, and adaptability to various environments make them effective in both augmentative and conservation biological control programs.

In sub-Saharan Africa, the most studied plant-inhabiting mite system is the cassava green mite complex, which has attracted extensive research since its introduction in the 1970s. The pest species Mononychellus tanajoa (Bondar) and Mononychellus progresivus Doreste (Acari: Tetranychidae) cause severe damage to cassava (Manihot esculenta Crantz), a staple crop for millions of people in the region [8]. The introduction of predatory mites (Phytoseiidae) from South America into Africa by the International Institute of Tropical Agriculture is one of the most successful examples of classical biological control against phytophagous mites. This program, implemented across West and Central Africa, demonstrated the effectiveness of natural enemies in restoring ecological balance and improving food security.

Early acarological research followed a similar trajectory in the RC. The initial studies were mainly descriptive and focused on phytophagous mites associated with cassava. The pioneering work of Bonato and his collaborators, carried out in the 1990s [9], provided the first detailed inventory of tetranychid mites in the country, particularly those infesting cassava crops in the southern regions (Kouilou, Bouenza, Pool, and Plateaux). Seven Tetranychidae species were recorded, among which Mononychellus progresivus and Oligonychus gossypii were identified as the main phytophagous species of agronomic importance. In parallel with the study of phytophagous mites, Guttierez and Bonato (1994) identified several species of predatory mites belonging to the family Phytoseiidae, which are known for their crucial roles in the natural regulation of Tetranychidae populations. Their survey identified six major species belonging to the genera Euseius, Typhlodromalus, Neoseiulus, and Amblyseius. These observations represent the first record of Phytoseiidae in the RC and highlight the presence of predatory fauna that is potentially useful for the biological control of cassava mite pests.

Guttierez and Bonato (1994) relied exclusively on morphological criteria for mite identification, which was the standard approach used at the time [9]. In parallel, Navajas et al. (1994) introduced the first molecular approaches applied to cassava mites, revealing intraspecific genetic diversity within M.progresivus [12]. This methodological transition has provided a foundation for integrating molecular markers to assess the taxonomy and ecology of phytophagous mites. However, despite the foundational nature of these morphological and molecular studies, no research has been published based on data collected from plant-inhabiting mites in the RC. Moreover, a prolonged period of low scientific output occurred between 1994 and 2018 with regard to plant-associated acarofauna in the RC. In the absence of biodiversity surveys conducted at the national scale during this interval, a few sporadic contributions, mostly of regional or taxonomic scope, nevertheless relied on congolese material, notably the redescription of Typhlodromalus aripo by Moraes et al. (2006) based on specimens originating from the RC [13]. Although limited in scope, these studies contributed to updating the available knowledge on plant-inhabiting mites in the RC. Research specifically dedicated to the inventory of plant-inhabiting mite biodiversity resumed with a Master’s thesis completed in 2018. This thesis is mentioned here to document the re-emergence of acarological research in the RC but was not included in the narrative review, which was restricted to peer-reviewed publications. The scientific valorization of these results in an international peer-reviewed journal in 2020 highlighted the need to address existing knowledge gaps for this taxonomic group and encouraged the initiation of new national-scale inventory projects. Accordingly, only the 2020 peer-reviewed article derived from this work was included in the present narrative review [22]. This study aimed to clarify the taxonomic status of severalEuseius populations collected from cassava, okra, and chili using a combination of morphometric and molecular analyses (12S rRNA and ITS genes). These recent investigations mark a turning point in the adoption of integrative taxonomy in congolese acarology, bridging the gap between traditional morphology-based studies and modern molecular narratives.

Therefore, a narrative literature review is timely and necessary to establish a baseline for acarological research in the RC. By consolidating and critically analysing existing data, this study aimed to clarify the current state of knowledge, highlight research gaps, and guide future investigations toward integrative approaches that combine morphological and molecular. The main objective of this study was to provide an updated synthesis of research on plant-inhabiting mites in the RC between 1980 and 2025. Specifically, the aims were as follows: 1) compile all available scientific literature on Tetranychidae and Phytoseiidae reported from the country; 2) identify the main species and their host plants, as well as their geographic distribution; 3) analyse the methodological evolution from morphological to molecular and integrative approaches; and 4) proposed research and management perspectives to strengthen acarological knowledge and promote the use of predatory mites in biological control programs in the RC.

This narrative review was designed to compile, evaluate, and synthesise existing scientific knowledge on plant-inhabiting mites (families, Phytoseiidae and Tetrany-chidae) reported in the RC from 1980 to 2025. This review followed the Preferred Reporting Items for Narrative Reviews and Meta-Analyses (PRISMA) principles, emphasising transparency, reproducibility, and comprehensive data retrieval.

Acarological research in the RC has evolved substantially over the past four decades, progressing from the early descriptive inventories of the 1980s to a more integrative and biodiversity-oriented phase since 2020. The pioneering work provided the first detailed account of plant-inhabiting mites in the country, focusing mainly on cassava (M. esculenta), a major subsistence crop [9]. Morphological surveys identified seven species of Tetranychidae and three species of Phytoseiidae (E. fustis, A. sundi, and T. saltus), providing a foundation for congolese acarological taxonomy. Later revisions [20] expanded this faunal list to include E. baetae and E. neodossei, whereas recent investigations [22][23] confirmed six Phytoseiidae species on cassava and associated crops in the Brazzaville region. Collectively, these findings illustrate a gradual transition from morphology-based inventories to integrative approaches that combine morphological and molecular diagnostics.

During the 1980s and 1990s, the morphological approach represented the global standard for mite identification. However, this methodology has intrinsic limitations, particularly in distinguishing between cryptic and morphologically similar species. A pioneering molecular study [12] on M. progresivus marked a turning point in African acarology, revealing intraspecific genetic variation and partial reproductive isolation among its populations. Although this study did not specifically address congolese fauna, it established a methodological framework for future molecular studies in the region.

Following this foundational phase, acarological research in the RC entered a hiatus of nearly two decades (1994-2020). The absence of publications during this period reflects the discontinuity of local research programs and limited institutional support for taxonomic and biodiversity studies. It was not until the early 2020s that new surveys revitalised the field, emphasising biodiversity assessments, integrative taxonomy and applications in biological control. Recently, Belle Mbou Okassa et al. (2020-2025) [22][23] refined the inventory of predatory mites on cassava and confirmed the presence of six Phytoseiidae species (E. fustis, A. sundi, T. saltus, E. baetae, E. neodossei, and I. degenerans). Parallel analyses updated the Tetrany-chidae fauna and identified M. progresivus and O. gossypii as the most prevalent phytophagous species on M. esculenta.

The advent of molecular biology in taxonomy has marked a major breakthrough in species identification, particularly since the pioneering work of Hebert et al. (2003), who introduced DNA barcoding as a reference approach to molecular narratives [25]. In acarology, the use of molecular tools has greatly contributed to resolving complex taxonomic issues, such as the validation of new species [26], and improvements in diagnostic reliability through their ability to distinguish interspecific differentiation from intraspecific variability [27]. In the congolese context, only one study has explored the potential of molecular barcoding to clarify the taxonomic status of specimens belonging to the genus Euseius. However, the reliability of molecular diagnoses strongly depends on the completeness and accuracy of reference databases, which remain limited for many mite taxa. This is the first study to use an integrative taxonomy approach, combining molecular analyses based on 12S rRNA and ITS gene sequences with morphological characterisation, and provides the first genetic characterisation of congolese populations of species belonging to the genus Euseius [22].

The faunal composition revealed by recent surveys highlights the strong biogeographical connections linking the mite communities of the RC to those of neighbouring Central African countries. Several dominant species recorded in RC, such as M. progresivus, E. fustis, and A. sundi are also prevalent in Cameroon, Gabon, and the Democratic Republic of Congo. This distribution pattern suggests that many species exhibit a pan-equatorial range, reflecting similar climatic conditions and widespread cultivation of cassava and other tropical crops.

M.progresivus is recognized as the primary mite pest of cassava in Central Africa and is associated with significant agronomic losses [9][18]. Field studies have shown that infestations can reduce cassava productivity by altering dry matter allocation to storage roots, even when foliar damage appears moderate [18], with reported yield losses ranging from approximately 13% to more than 80% under severe outbreaks. Oligonychus gossypii is another phytophagous mite of agronomic relevance in congolese agroecosystems, infesting cassava as well as cotton and vegetable crops [9][17][18]. Its feeding activity causes chlorosis, premature leaf senescence, and reduced photosynthetic capacity, and recurrent infestations suggest a contribution to cumulative yield losses under favourable conditions [16][18].

The recent detection of E. orientalis in Brazzaville is noteworthy. Originally native to Asia and the Middle East, this polyphagous species has expanded across Africa and the Mediterranean Basin in recent decades. Its occurrence in the RC likely represents a recent introduction or range extension, possibly facilitated by the regional trade of citrus and ornamental plant. Given its polyphagy and defoliation potential, E. orientalis warrants monitoring as an emerging pest in the congolese horticultural system.

Conversely, the relatively high diversity of Phytoseiidae, particularly within Euseius and Amblyseius, reflects favourable ecological conditions for predatory mites in humid tropical environments. These taxa are known for their adaptability to diverse microhabitats, tolerance of pollen-based diets, and persistence during periods of low prey density. Their consistent occurrence on cassava and solanaceous crops indicates a strong potential for the natural regulation of Tetranychidae populations, which merits confirmation through field-based studies on predator-prey interactions.

Overall, these findings provide a comprehensive overview of the current state of acarological research in the RC. They highlight both the scientific progress achieved and the persistent challenges that must be addressed. The transition toward integrative taxonomy represents a decisive step forward, aligning local acarological studies with international standards and providing a foundation for sustainable pest management and biodiversity conservation across Central African agroecosystems.

Perspectives

Future research in acarology in the RC should focus on three complementary axes: expanding taxonomic knowledge, strengthening molecular identification tools, and establishing scientific networks dedicated to mite biodiversity. In particular, large areas of northern Congo remain virtually unexplored from an acarological perspective, and baseline surveys in these regions would substantially improve current knowledge of species distributions and host associations.

From a methodological perspective, the generalization of DNA barcoding approaches [25] represents a major advance in improving the reliability of taxonomic diagnostics and resolving the morphological ambiguities that remain common among Phytoseiidae and Tetranychidae. Since the late 2000s, several studies have defined genetic divergence thresholds that serve to distinguish intra- from interspecific variation in mites. For Phytoseiidae, analyses based on mitochondrial genes such as COI and 12S rRNA have shown that intraspecific divergences are generally below 2%, while interspecific divergences often exceed 8% - 12%, confirming the existence of a barcoding gap that can be used for species delimitation and molecular diagnosis [22][26]-[29]. Priority should be given to genera already reported from the country and suspected to include cryptic species complexes, such as Euseius, Typhlodromalus and Amblyseius among Phytoseiidae, and Mononychellus, Oligonychus and Tetranychus among Tetranychidae. These thresholds now represent key benchmarks for the molecular validation of species boundaries.

However, the performance of DNA barcoding strongly depends on the completeness and quality of reference databases used for sequence comparison. Insufficient taxonomic or geographic coverage can lead to misidentifications or ambiguous assignments, thus limiting the ecological interpretation of results [30][31].

In this context, the establishment of regional barcode libraries integrating morphologically validated and georeferenced specimens is a priority. As emphasized by [32] the effectiveness of barcoding depends not only on the number of available sequences but also on their traceability, the quality of associated metadata, and the inclusion of voucher specimens preserved in reference collections. Such an approach would ensure the reproducibility of analyses and enhance comparability among laboratories.

The creation of a national reference database for the acarofauna of the RC would therefore represent a strategic step forward. This database could rely on standardized gene sequences (COI, 12S rRNA, ITS) obtained from local populations, coupled with detailed morphological and ecological data. Ultimately, such an infrastructure would help fill existing gaps in international databases like BOLD [31] or GenBank [32] where African fauna remains largely underrepresented.

Finally, the development of training programs and regional collaborations involving congolese institutions, African research centers, and international partners is essential to ensure the sustainability of these initiatives. Strengthening expertise in integrative taxonomy, bioinformatics, and molecular biology will anchor congolese acarology within global biodiversity research networks. In the short term, these efforts would primarily support accurate species identification and biodiversity assessment, while in the longer term they would provide a robust framework for ecological studies and sustainable pest management strategies.

In summary, the combination of morphological, molecular, and ecological approaches, supported by reliable databases and strong institutional partnerships, will pave the way for a deeper understanding and sustainable management of phytophagous and predatory mites in Central African agroecosystems.

Over the past four decades, acarological research in the RC has progressed from descriptive inventories to integrative studies combining morphology and molecular tools. The synthesis of available data revealed 22 species of plant-inhabiting 10 mites of Phytoseiidae and 12 of Tetranychidae mainly associated with cassava and other economically important crops. Among these, E. fustis and I. degenerans have emerged as key predatory species with potential applications in biological control, whereas M. progresivus remains the dominant phytophagous pest.

Despite these advances, significant gaps persist, particularly regarding the northern and central regions of the country, molecular phylogenetic data, and long-term monitoring of predator prey dynamics. Strengthening acarological research will require the establishment of specialised laboratories, the development of reference collections, and training of new experts in integrative taxonomy. Beyond its agronomic implications, studying mites in the RC contributes to a broader understanding of tropical biodiversity and ecosystem functions. By linking taxonomy, ecology, and applied research, acarology can play a pivotal role in promoting sustainable pest management and biodiversity conservation in Central African agroecosystems.