The species, density, and intra-plant distribution of mites on red raspberry (Rubus idaeus L.)

The adoption of the European Green Deal will limit acaricide use in high value crops like raspberry, to be replaced by biological control and other alternative strategies. More basic knowledge on mites in such crops is then necessary, like species, density, and their role as vectors of plant diseases. This study had four aims, focusing on raspberry leaves at northern altitude: (1) identify mite species; (2) study mite population densities; (3) investigate mite intra-plant distribution; (4) investigate co-occurrence of phytophagous mites, raspberry leaf blotch disorder and raspberry leaf blotch virus (RLBV). Four sites in south-eastern Norway were sampled five times. Floricanes from different parts of the sites were collected, taking one leaf from each of the upper, middle, and bottom zones of the cane. Mites were extracted with a washing technique and processed for species identification and RLBV detection. Mites and leaves were tested for RLBV by reverse transcription polymerase chain reaction (RT-PCR) with virus-specific primers. Phytophagous mites, Phyllocoptes gracilis, Tetranychus urticae, and Neotetranychus rubi, and predatory mites, Anystis baccarum and Typhlodromus (Typhlodromus) pyri were identified. All phytophagous mites in cultivated raspberry preferred the upper zone of floricanes, while in non-cultivated raspberry, they preferred the middle zone. The presence of phytophagous mites did not lead to raspberry leaf blotch disorder during this study. RLBV was detected in 1.3% of the sampled plants, none of them with leaf blotch symptoms, and in 4.3% of P. gracilis samples, and in some spider mite samples, implying that Tetranychids could also be vectors of RLBV.

Impact of agroecological practices on Phytoseiidae communities in a vineyard of South of France: effect of covercrops and agroforestry

Viticulture is characterized by substantial pesticide applications, impacting natural enemies. New pest control strategies and management of plant diversity into agrosystems acting as reservoirs of natural enemies are assumed to limit pesticide use. Various studies support this hypothesis but gaps exist on the effect of diversification on Phytoseiidae mites, generalist predators reported as prevalent and efficient natural enemies in vineyards. This study focuses on the effect of cover crop management (no cover crop, spontaneous cover crops with or without agroforestry) and grape variety (resistant cv. Artaban and cv. Syrah) on predatory mites and prey communities, in a newly planted experimental vineyard in South-East France. Samplings were carried out three times a year on vine, cover crops, and co-planted trees. Phytoseiidae, Tydeiidae, Eriophyidae mites and thrips were characterized. Nine Phytoseiidae species were identified on vine, the main ones being Kampimodromus aberrans, Typhlodromus exhilaratus, Phytoseius finitimus and Euseius gallicus. Kampimodromus aberrans was prevalent on the cv. Syrah, highlighting a strong effect of variety. The low unexpected effect of system management observed outcome could be due to several factors, such as the experimental plot size or the influence of vine stress on Phytoseiidae communities in vines with cover crops. All phytoseiid species present on vine were identifed at least once on cover crops and co-planted trees, suggesting their potential role as reservoirs. Further studies should be performed investigating the evolution of communities in this newly-planted experimental system, as well as potential differences in trophic network interactions.

Acute toxicity effects of pesticides on predatory snout mites (Trombidiformes: Bdellidae)

Predatory mites biologically control a range of arthropod crop pests and are often central to agricultural IPM strategies globally. Conflict between chemical and biological pest control has prompted increasing interest in selective pesticides with fewer off-target impacts on beneficial invertebrates, including predatory mites. However, the range of predatory mite species included in standardized pesticide toxicity assessments does not match the diversity of naturally occurring species contributing to biocontrol, with most testing carried out on species from the family Phytoseiidae (Mesostigmata). Here, we aim to bridge this knowledge gap by investigating the impacts of 22 agricultural pesticides on the predatory snout mite, Odontoscirus lapidaria (Kramer) (Trombidiformes: Bdellidae). Using internationally standardized testing methodologies, we identified several active ingredients with minimal impact on O. lapidaria mortality, including Bacillus thuringiensis, nuclear polyhedrosis virus, flonicamid, afidopyropen, chlorantraniliprole, and cyantraniliprole, which may therefore be good candidates for IPM strategies utilizing both chemical and biological control. Comparison of our findings with previous studies on Phytoseiid mites reveals important differences in responses to a number of chemicals between predatory mite families, including the miticides diafenthiuron and abamectin, highlighting the risk of making family-level generalizations from acute toxicity assessments. We also tested the impacts of several pesticides on a second Bdellidae species (Trombidiformes: Bdellidae) and found differences in the response to chlorpyrifos compared with O. lapidaria, further highlighting the taxon-specific nature of nontarget toxicity effects.

An exploratory analysis of the structure of tetranychid and phytoseiid assemblages in walnut orchards in California

Spider mites were considered secondary pests of walnut production in California, under the control of phytoseiid predators. Due to increased importance as walnut pests in recent decades there is renewed interest in the structure and function of the associated phytoseiid assemblage. In this study we report the results from a 3 year survey of the tetranychid and phytoseiid assemblages in walnut orchards in the Central Valley of California. The survey was conducted to determine the range and dominance of web-spinning Tetranychus species present, to investigate the species richness and dominance of the phytoseiid species present, and to explore whether patterns of variation in the relative abundance of phytoseiid species could be explained by one or more explanatory variables. Tetranychus urticae was the dominant spider mite in all growing regions and years with T. pacificus and T. turkestani also present in orchards in the southern San Joaquin Valley. Phytoseiid species richness declined with latitude among the three walnut growing regions and of the 13 species found Amblyseius similoides, Euseius stipulatus, Galendromus occidentalis and Typhlodromus caudiglans were the most abundant and widespread species present. Mean proportional abundance significantly increased from early (mid May-July) to late (August-mid October) season and from southern to northern growing regions for Type II and IV predators, but significantly decreased from early to late season and from southern to northern growing regions for Type III predators. The mean proportional abundance of Type II predators, particularly G. occidentalis, significantly increased and that of Type III predators significantly decreased with mean Tetranychus density in individual orchards. The current survey provides a more in-depth analysis of mite assemblages in walnut orchards in California and can be used to better inform adaptive management strategies for integrated mite management in the future.

Mite fauna on apples in southern Brazil - Review and perspectives

Brazil is among the largest apple producers in the world (Malus domestica Bork, Rosaceae), with production concentrated mainly in the southern of the country. Panonychus ulmi (Koch) (Tetranychidae) have economic importance in apple and, recently, Aculus schlechtendali (Nalepa) (Eriophyidae), was reported in Brazil. This review aims to delineate the distribution of the acarofauna associated to apple, with emphasis on the main groups of economic importance and their potential natural enemies and highlight the problems related to phytophagous species and management possibilities. Searches were carried out in databases, and the principal keywords were Aculus schlechtendali, Malus domestica and Panonychus ulmi. After the exclusion criteria resulted 166 publications. The social and economic importance of the apple has been increasing on the world, however, due to environmental imbalance, phytophagous mites are increasing their populations and acquiring resistance against acaricides. Panonychus ulmi has been reported in America for decades, being of economic importance for Brazil and the record of A. schlechtendali alerts to the possibility of damage in orchards in the country. Therefore, it is important that the literature be evaluated, that the mite species are identified and that forms of conscious management are developed. Prioritizing the human and animal health and environmental balance.

Current Status of Phytoseiid Mites as Biological Control Agents in Latin America and Experiences from Argentina Using Neoseiulus californicus

Phytoseiidae is a large family of Mesostigmata mites. Members of this family are important biological control agents across the world since they are well-known natural enemies of phytophagous arthropods on cultivated and non-cultivated plants, mainly used to control pest spider mites. However, some can control thrips in greenhouses and fields. Several studies reporting on species in Latin America have been published. The most extensive studies were conducted in Brazil. Phytoseiid mites have been used in different biological control approaches, with two successful classical biological control programs: the biocontrol of the cassava green mite using Typhlodromalus aripo (Deleon) in Africa and the citrus and avocado mites by Euseius stipulatus (Athias-Henriot) in California. Efforts in using phytoseiid mites to enforce biological control of different phytophagous mites are being made in Latin America. Till now, only a few successful examples are available on this topic. This fact highlights the need to continue the investigations on the ability of other unknown species to be used in biological control through close collaboration between researchers and biocontrol companies. Various challenges remain, such as developing better rearing systems to provide a large number of predators to farmers in various crop systems, training farmers to improve their understanding of the use of predators, and chemical control aimed at conservation biological control, looking forward to increasing the use of the phytoseiid mites as biological control agents in Latin America and the Caribbean.

Do mites eat and run? A systematic review of feeding and dispersal strategies

Dispersal is an important process affecting the survival of organisms and the structure and dynamics of communities and ecosystems in space and time. It is a multiphase phenomenon influenced by many internal and external factors. Dispersal syndromes can be complicated, but they are vital to our knowledge of the biology of any organism. We analysed dispersal ability in mites (Acariformes and Parasitiformes), a highly diverse group of wingless arthropods, taking into consideration various modes of dispersal, feeding strategies, body size and the number of articles published for each species. Based on 174 articles summarized for this study, it appears that mites are opportunistic when it comes to dispersal, regardless of their feeding habits, and are often able to adopt several different strategies as needs arise. Moreover, we find a significant positive relationship between the amount of research effort that was put into studying a given species and the number of modes of dispersal that were described. The most salient conclusion to be drawn from this positive correlation is that additional studies are needed, especially on a broader set of mite taxa, until the aforementioned correlation is no longer demonstrably significant.

Pesticides monitoring in biological fluids: Mapping the gaps in analytical strategies

Pesticides play a key-role in the development of the agrifood sector allowing controlling pest growth and, thus, improving the production rates. Pesticides chemical stability is responsible of their persistency in environmental matrices leading to bioaccumulation in animal tissues and hazardous several effects on living organisms. The studies regarding long-term effects of pesticides exposure and their toxicity are still limited to few studies focusing on over-exposed populations, but no extensive dataset is currently available. Pesticides biomonitoring relies mainly on chromatographic techniques coupled with mass spectrometry, whose large-scale application is often limited by feasibility constraints (costs, time, etc.). On the contrary, chemical sensors allow rapid, in-situ screening. Several sensors were designed for the detection of pesticides in environmental matrices, but their application in biological fluids needs to be further explored. Aiming at contributing to the implementation of pesticides biomonitoring methods, we mapped the main gaps between screening and chromatographic methods. Our overview focuses on the recent advances (2016-2021) in analytical methods for the determination of commercial pesticides in human biological fluids and provides guidelines for their application.

Itching for an Answer: Gall-Forming Biological Control Agent Contains an Itch Mite Species Found at Localities Known for Periodic ‘Bite Outbreaks’

Biological control is an attractive option for controlling invasive plant species that are difficult to manage otherwise. However, the release of a non-native species as a biological control agent carries risks. The most obvious risk relates to impacts on plant species other than the plant species targeted for control. There are, however, also other risks. We report on a potential unintended impact of Dasineura dielsi, a gall-forming biological control agent that was released against Acacia cyclops in South Africa in 2003. We confirmed that the galls formed by D. dielsi on A. cyclops harbor mites in the genus Pyemotes (P. cf. ventricosus) within their gall structures, which are parasites of various insect species, but are also known to cause dermatitis in humans. Sporadic biting incidences have been reported in at least two locations in South Africa. The implications are that manual clearing of A. cyclops may expose humans to itch mites and to risks of bites. Gall-forming insects and fungi are known to create niches for herbivores and other gall-associated fauna. Although every possible food web interaction cannot be predicted, enough evidence exists to require that agent screening to include non-target risks other than those pertaining to non-host plants. Testing only whether agents are compromised by interactions with non-target plant species is not sufficient during agent evaluation. If such associations are known from the native range and therefore can form in the introduced range, then any known risk to health and socio-economic activities should be disclosed. We argue for the general development of objective assessment of such risks compared with the benefits potentially accruing from successful biological control of the target plant.

Drivers for mutation in amino acid sequences of two mitochondrial proteins (Cytb and COI) in Phytoseiidae mites (Acari: Mesostigmata)

Mutations in amino acid sequences can affect protein function. Such aspects have been poorly studied for arthropods. As recent studies have shown mutations in cytochrome b (Cytb) associated with geographic locations in several Phytoseiidae species, the present study aims at investigating (i) the mutation pattern in additional species for the Cytb fragment, (ii) the mutation pattern for another mitochondrial amino acid sequence, cytochrome c oxidase subunit 1 (COI), and (iii) factors affecting the mutations observed (taxonomy, plant support, climatic variables, wild vs. commercialised species). Mutations in amino acid sequences were assessed in seven Phytoseiidae species, with populations collected in contrasted environments. The DNA sequences were mainly obtained from published studies and some were newly obtained. Mutations were observed within and between the populations considered for both fragments, with higher mutation rates in Cytb than in COI sequences, confirming the robustness of this former fragment. Plant support and taxonomic position were not related to mutation patterns. A lower number of mutations was observed in commercialised populations than in wild ones. As preliminary tendencies, mutations in Cytb and COI sequences seem associated to temperature and moisture. Such a preliminary approach, attempting to relate mutation to functional adaptations, clearly opens new research tracks for better assessment of the drivers of mite adaptation, in a context of climate change.

Known and Potential Invertebrate Vectors of Raspberry Viruses

The estimated global production of raspberry from year 2016 to 2020 averaged 846,515 tons. The most common cultivated Rubus spp. is European red raspberry (Rubus idaeus L. subsp. idaeus). Often cultivated for its high nutritional value, the red raspberry (Rubus idaeus) is susceptible to multiple viruses that lead to yield loss. These viruses are transmitted through different mechanisms, of which one is invertebrate vectors. Aphids and nematodes are known to be vectors of specific raspberry viruses. However, there are still other potential raspberry virus vectors that are not well-studied. This review aimed to provide an overview of studies related to this topic. All the known invertebrates feeding on raspberry were summarized. Eight species of aphids and seven species of plant-parasitic nematodes were the only proven raspberry virus vectors. In addition, the eriophyid mite, Phyllocoptes gracilis, has been suggested as the natural vector of raspberry leaf blotch virus based on the current available evidence. Interactions between vector and non-vector herbivore may promote the spread of raspberry viruses. As a conclusion, there are still multiple aspects of this topic that require further studies to get a better understanding of the interactions among the viral pathogens, invertebrate vectors, and non-vectors in the raspberry agroecosystem. Eventually, this will assist in development of better pest management strategies.

Acarofauna present in organic strawberry fields and associated weed species in southern Brazil

The presence of weeds in the margins of strawberry crops can enhance populations of predatory mites as a measure to support conservation biological control. The aims of this study were (i) to assess the composition of the acarofauna associated with strawberries and the accompanying herbaceous plants in an organic farming system, and (ii) to evaluate the possible relationships between phytophagous and predatory mites occurring in this system. Strawberry leaves and whole plants of weeds were sampled biweekly from August 2014 to February 2015 in Lapa (Paraná, Brazil). In total, 23 weed species belonging to 10 families were identified; 3768 mite individuals (from 15 families and 4 suborders) were recovered, 77% on strawberries and 23% on weeds. Abundance of predatory mites on weeds was greater than on strawberry cultivars. On strawberries, the most abundant family was Tetranychidae (84%) followed by Phytoseiidae (11.6%). In total, 16 predatory mite species from the Phytoseiidae family were identified, 13 of them occurring on strawberry leaflets. Typholodromalus aripo, Neoseiulus californicus and Typhlodromips mangleae were the most abundant mite species on strawberry leaves. On weeds, most individuals were predatory mites (59%), whereas phytophagous mites represented 17.2%. The most abundant family was Phytoseiidae (36.4%). On weeds, the phytoseiid mite T. aripo was the most abundant species, representing 34.7%. Besides being found on strawberry leaflets, T. aripo was associated with 15 weed species. Among the weeds, Bidens pilosa showed the highest values of the Shannon index (1.97), Margalef index (3.04), and Pielou's evenness index (0.95). This study emphasizes the importance of surrounding weeds as a shelter for beneficial mitefauna in strawberry fields, likely contributing to enhance conservation biological control.

Side Effects of Sulfur Dust on the European Grapevine Moth Lobesia botrana and the Predatory Mite Kampimodromus aberrans in Vineyards

To reduce the impact of synthetic insecticides on human health and the environment, eco-friendly alternatives must be investigated. Knowledge of the side effects on pests and natural enemies of natural products applied to vineyards is very useful. Sulfur dust, which is used in vineyards to control powdery mildew, is investigated in laboratory and field bioassays for its effects on Lobesia botrana egg laying, egg hatching, and larval settlement. In field trials, the efficacy of sulfur dust against the two L. botrana carpophagous generations is compared with that of Bacillus thuringiensis and kaolin, and its side effects on the phytoseiid mite Kampimodromus aberrans are evaluated. In the bioassays, sulfur dust reduced female survival by 43%, egg laying by around 80%, egg hatching by 10%, and larval settlement by 55%. In field trials, sulfur dust caused a significant decrease in the number of L. botrana larval nests of both generations, even though the efficacy was lower than that of B. thuringiensis. No negative effects of sulfur dust on the predatory mite population density was observed. On the basis of these results, in the context of Integrated Pest Management strategies in vineyards, the activity of sulfur dust against L. botrana could be exploited by timing its application to the beginning of egg laying.

Markers of life history traits: variation in morphology, molecular and amino acid sequences within Typhlodromus (Anthoseius) recki Wainstein (Acari: Mesostigmata: Phytoseiidae)

In this study we investigated morphological and molecular variation within the predatory mite Typhlodromus (Anthoseius) recki, and their relationships to ecological features. In total, 42 morphological characters were measured on 87 specimens from seven populations in the south of France and Sicily living on plants of four families. DNA sequences (two mitochondrial markers) and the amino acid sequences of the CytB protein were assessed. A relationship between morphological variation and plant families was observed. The 12S rRNA gene showed differentiation that appeared to be related to feeding habit, in agreement with the findings for two other Phytoseiidae species. CytB mitochondrial DNA showed variation related to geographical location. Four amino acid mutations separated the Sicilian and the French populations. CytB amino acid sequences were analysed for three other Phytoseiidae species, and again diagnostic mutations associated with geographical location were observed, as already shown for Phytoseiulus macropilis. The population differentiation observed for each marker (morphological, DNA fragments) appeared to be related to ecological/biological features, revealing new perspectives for forecasting functional characteristics based on morphotypes and genotypes. However, additional studies are needed to confirm these observations and to explain such functional relationships.

Molecular characterization of phytoseiid mites in Turkey based on the internal transcribed spacer (ITS) region, with a new record for the country

The family Phytoseiidae contains many predatory mite species and some are used in biological control programs worldwide. The identification of phytoseiid mites is based on tiny morphological structures and sometimes species diagnosis is not easy especially for non-taxonomists. DNA-based approaches may offer a fast and accurate diagnosis to overcome these difficulties, nevertheless more DNA sequences are needed to determine intra- and inter-specific variations and to provide accurate decision rules based on genetic distances between the taxa considered. In this study, we provide the molecular characterization of seven phytoseiid species based on the internal transcribed spacer (ITS) region. Several populations of these species collected in Turkey were considered. A phylogenetic tree was also constructed. Finally, we record the presence of Neoseiulus reductus (Wainstein) in Turkey.

Improving the compatibility of pesticides and predatory mites: recent findings on physiological and ecological selectivity

Integrated pest management relies upon the application of selective pesticides that do not hinder biological control. Phytoseiid mites represent an interesting case-study: they are amongst the most frequently used biological control agents and often are less affected by pesticides than their prey by natural tolerance or by developing resistance. The selectivity of a pesticide is determined by physiological processes that include metabolism, transport, and the affinity to the target-site. Genomic and transcriptomic studies start to elucidate the genetic and molecular mechanisms of differential toxicity in some phytoseiid species, such as a mutation in the sodium channel conferring pyrethroid resistance. Ecological selectivity is achieved by smart applications of pesticides and management practices that influence the persistence of phytoseiid mites on plants. Although modern pesticides often show lower acute toxicity, there is a need for robust assays and procedures that quantify lethal and sublethal effects, through different routes and times of exposure.