Three New Species of Aceria (Acari: Trombidiformes: Eriophyoidea) from China

Three new Aceria species from South China are described and illustrated. Aceria bischofiaesp. nov. was collected on Bischofia javanica Blume (Phyllanthaceae), inducing galls on surfaces of the leaves; Aceria cryptocaryaesp. nov. was collected on Cryptocarya metcalfiana Allen (Lauraceae), causing the formation of erinea on the undersurface of the leaves; and Aceria buddlejaesp. nov. was collected as a vagrant on Buddleja lindleyana Fort. (Scrophulariaceae) leaves, and no symptoms were observed on the host plant.

Genetic analysis of the tomato russet mite provides evidence of oligophagy and a widespread pestiferous haplotype

Worldwide, the tomato russet mite (TRM), Aculops lycopersici (Eriophyidae), is a key pest on cultivated tomato in addition to infesting other cultivated and wild Solanaceae; however, basic information on TRM supporting effective control strategies is still lacking, mainly regarding its taxonomic status and genetic diversity and structure. As A. lycopersici is reported on different species and genera of host plants, populations associated with different host plants may constitute specialized cryptic species, as shown for other eriophyids previously considered generalists. The main aims of this study were to (i) confirm the TRM taxonomic unity of populations from different host plants and localities as well as the species' oligophagy, and (ii) to advance the understanding of TRM host relationship and invasion history. For this purpose, we evaluated the genetic variability and structure of populations from different host plants along crucial areas of occurrence, including the area of potential origin, based on DNA sequences of mitochondrial (cytochrome c oxidase subunit I) and nuclear (internal transcribed spacer, D2 28S) genomic regions. Specimens from South America (Brazil) and Europe (France, Italy, Poland, The Netherlands) were collected from tomato and other solanaceous species from the genera Solanum and Physalis. Final TRM datasets were composed of 101, 82 and 50 sequences from the COI (672 bp), ITS (553 bp) and D2 (605 bp) regions, respectively. Distributions and frequencies of haplotypes (COI) and genotypes (D2 and ITS1) were inferred; pairwise genetic distance comparisons, and phylogenetic analysis were performed, including Bayesian Inference (BI) combined analysis. Our results showed that genetic divergences for mitochondrial and nuclear genomic regions from TRM associated with different host plants were lower than those observed in other eriophyid taxa, confirming conspecificity of TRM populations and oligophagy of this eriophyid mite. Four haplotypes (cH) were identified from the COI sequences with cH1 being the most frequent, representing 90% of all sequences occurring in all host plants studied (Brazil, France, The Netherlands); the other haplotypes were present exclusively in Brazilian populations. Six variants (I) were identified from the ITS sequences: I-1 was the most frequent (76.5% of all sequences), spread in all countries and associated with all host plants, except S. nigrum. Just one D2 sequence variant was found in all studied countries. The genetic homogeneity among populations highlights the occurrence of a highly invasive and oligophagous haplotype. These results failed to corroborate the hypothesis that differential symptomatology or damage intensity among tomato varieties and solanaceous host plants could be due to the genetic diversity of the associated mite populations. The genetic evidence, along with the history of spread of cultivated tomato, corroborates the hypothesis of a South American origin of TRM.

Anatomy of the miniature four-legged mite Achaetocoptes quercifolii (Arachnida: Acariformes: Eriophyoidea)

Miniaturization is one of the important trends in the evolution of terrestrial arthropods. In order to study adaptations to microscopic sizes, the anatomy of the smallest insects was previously studied, but not the anatomy of the smallest mites. Some of the smallest mites are Eriophyidae. In this study we describe for the first time the anatomy of the mite Achaetocoptes quercifolii, which is about 115 μm long. For this purpose, we used light, scanning, and transmission electron microscopy and performed 3D reconstructions. The anatomy of A. quercifolii is compared with the anatomy of larger representatives of Eriophyoidea. Despite the small size of the studied species, there is no considerable simplification of its anatomy compared to larger four-legged mites. A. quercifolii has a number of miniaturization effects similar to those found in microinsects: a strong increase in the relative volume of the reproductive system, an increase in the relative volume of the brain, reduction in the number and size of cells of the nervous system. As in some larger four-legged mites, A. quercifolii undergoes midgut lysis at the stage of egg production. On the other hand, in A. quercifolii a greater number of opisthosomal muscles are preserved than in larger gall-forming four-legged mites.

Enhanced top-down control of herbivore population growth on plants with impaired defences

Herbivore densities can be regulated by bottom-up and top-down forces such as plant defences and natural enemies, respectively. These forces can interact with each other to increase plant protection against herbivores; however, how much complementarity exists between bottom-up and top-down forces still remains to be fully elucidated. Particularly, because plant defences can hinder natural enemies, how these interactions affect herbivore performance and dynamics remains elusive.To address this topic, we performed laboratory and greenhouse bioassays with herbivorous mite pests and predatory mites on mutant tomato plants that lack defensive hairs on stems and leaves. Particularly, we investigated the behaviour and population dynamics of different phytophagous mite species in the absence and presence of predatory mites.We show that predatory mites do not only perform better on tomatoes lacking defensive hairs but also that they can suppress herbivore densities better and faster on these hairless plants. Hence, top-down control of herbivores by natural enemies more than compensated the reduced bottom-up herbivore control by plant defences.Our results lead to the counter-intuitive insight that removing, instead of introducing, plant defence traits can result in superior protection against important pests through biological control. Read the free Plain Language Summary for this article on the Journal blog.

Hitchhiking or hang gliding? Dispersal strategies of two cereal-feeding eriophyoid mite species

Dispersal shapes the dynamics of populations, their genetic structure and species distribution; therefore, knowledge of an organisms' dispersal abilities is crucial, especially in economically important and invasive species. In this study, we investigated dispersal strategies of two phytophagous eriophyoid mite species: Aceria tosichella (wheat curl mite, WCM) and Abacarus hystrix (cereal rust mite, CRM). Both species are obligatory plant parasites that infest cereals and are of economic significance. We investigated their dispersal success using different dispersal agents: wind and vectors. We hypothesised that in both mite species the main mode of dispersal is moving via wind, whereas phoretic dispersal is rather accidental, as the majority of eriophyoid mite species do not possess clear morphological or behavioural adaptations for phoresy. Results confirmed our predictions that both species dispersed mainly with wind currents. Additionally, WCM was found to have a higher dispersal success than CRM. Thus, this study contributes to our understanding of the high invasive potential of WCM.

Is the emerging mite pest Aculops lycopersici controllable? Global and genome-based insights in its biology and management

Over the last decade, the tomato russet mite, Aculops lycopersici, has become a major pest in tomato crops worldwide, both in open-field and protected cultivation. Its minute size of 150 to 200 μm complicates early detection and monitoring in tomato crops. Passive dispersal occurs via air currents, crop management practices and commercial trade. Chemical control of Aculops lycopersici is difficult. Altered product use from broad spectrum pesticides towards selective acaricides, to meet integrated pest management (IPM) standards, has created better conditions for the rapid expansion of this specialized eriophyid mite. Moreover, practical implementation of promising natural enemies is challenging due to the complexity of biological control in tomato crops. Trichomes on tomato negatively affect arthropod natural enemies, but provide a refuge for the tomato russet mite. Despite the cosmopolitan nature of Aculops lycopersici, knowledge associated with IPM is limited and fragmented. This review describes fundamental biological data on Aculops lycopersici from the last 20 years and novel developments in the field of prevention, monitoring, chemical and biological control. The recent analysis of the genome sequence will be helpful in the development of a sustainable control strategy for Aculops lycopersici. © 2021 Society of Chemical Industry.

Eriophyid Mites in Classical Biological Control of Weeds: Progress and Challenges

A classical biological control agent is an exotic host-specific natural enemy, which is intentionally introduced to obtain long-term control of an alien invasive species. Among the arthropods considered for this role, eriophyid mites are likely to possess the main attributes required: host specificity, efficacy, and long-lasting effects. However, so far, only a few species have been approved for release. Due to their microscopic size and the general lack of knowledge regarding their biology and behavior, working with eriophyids is particularly challenging. Furthermore, mites disperse in wind, and little is known about biotic and abiotic constraints to their population growth. All these aspects pose challenges that, if not properly dealt with, can make it particularly difficult to evaluate eriophyids as prospective biological control agents and jeopardize the general success of control programs. We identified some of the critical aspects of working with eriophyids in classical biological control of weeds and focused on how they have been or may be addressed. In particular, we analyzed the importance of accurate mite identification, the difficulties faced in the evaluation of their host specificity, risk assessment of nontarget species, their impact on the weed, and the final steps of mite release and post-release monitoring.

Unexpected Effects of Local Management and Landscape Composition on Predatory Mites and Their Food Resources in Vineyards

Viticultural practices and landscape composition are the main drivers influencing biological pest control in vineyards. Predatory mites, mainly phytoseiid (Phytoseiidae) and tydeoid mites (Tydeidae), are important to control phytophagous mites (Tetranychidae and Eriophyidae) on vines. In the absence of arthropod prey, pollen is an important food source for predatory mites. In 32 paired vineyards located in Burgenland/Austria, we examined the effect of landscape composition, management type (organic/integrated), pesticide use, and cover crop diversity of the inter-row on the densities of phytoseiid, tydeoid, and phytophagous mites. In addition, we sampled pollen on vine leaves. Typhlodromus pyri Scheuten was the main phytoseiid mite species and Tydeus goetzi Schruft the main tydeoid species. Interestingly, the area-related acute pesticide toxicity loading was higher in organic than in integrated vineyards. The densities of phytoseiid and tydeoid mites was higher in integrated vineyards and in vineyards with spontaneous vegetation. Their population also profited from an increased viticultural area at the landscape scale. Eriophyoid mite densities were extremely low across all vineyards and spider mites were absent. Biological pest control of phytophagous mites benefits from less intensive pesticide use and spontaneous vegetation cover in vineyard inter-rows, which should be considered in agri-environmental schemes.

Impact of Aceria alhagi (Acari: Eriophyidae) as a potential biological control agent on the invasive weed Alhagi maurorum (Fabaceae) in its native range

Camelthorn, Alhagi maurorum Medik. (Fabaceae, Leguminosae), a native component of the Asian flora, is invasive in Australia, South Africa and the USA where it is considered a noxious weed in several states. To date there is no biological control program against this weed; however, initial investigations into potential biocontrol agents revealed an eriophyid mite, Aceria alhagi Vidović & Kamali, causing considerable damage in the native range. The mite attacks the growing tips as well as the flowers of the plants, not only reducing height and plant vigor but also reducing seed set. To assess the host range and impact of this potential biological control agent, on the target weed, no-choice tests as well as an open-field impact experiment were conducted at the research farm of the School of Agriculture, Shiraz University, Shiraz, Iran, over 2 years (2018 and 2019). Results from the no-choice tests suggest that A. alhagi poses negligible risk to the non-target plants tested in this study. In the first year of the open field impact test, plants did not flower; however, plant height was significantly reduced by mite attack. In the second year, significant reductions in plant biomass (26%), seed production (95%) and photosynthesis (53%) were observed in response to mite attack that would potentially limit the competitiveness of camelthorn as well as long-distance dispersal through seed in the invaded range. These results suggest that A. alhagi is a promising candidate for the biological control of camelthorn and should be prioritized for any future studies, expanding on the host range testing and safety.

Interactions between Two Biological Control Agents on Lygodium microphyllum

Lygodium microphyllum (Lygodiaceae) is an invasive climbing fern in peninsular Florida. Two classical biological control agents are currently being released against L. microphyllum: a leaf galling mite, Floracarus perrepae (Acariformes: Eriophyidae), and a moth, Neomusotima conspurcatalis (Lepidoptera: Crambidae). Little is known about how the two species interact in the field; thus we conducted oviposition choice tests to determine the effects of F. perrepae presence on oviposition behavior in N. conspurcatalis. Further, we conducted feeding trials with N. conspurcatalis larvae to establish the effects of gall presence on larval survival and rate of development, and determine whether N. conspurcatalis larvae would directly consume F. perrepae galls. Neomusotima conspurcatalis laid significantly more eggs on mite galled (52.66 ± 6.211) versus ungalled (34.40 ± 5.587) L. microphyllum foliage. Feeding trials revealed higher mortality in N. conspurcatalis larvae raised on galled (60%) versus ungalled (36%) L. microphyllum material. In gall feeding trials, N. conspurcatalis larvae consumed or damaged 13.52% of galls, and the rate of direct gall feeding increased over time as leaf resources were depleted. Our results suggest that, where N. conspurcatalis and F. perrepae co-occur, competitive interactions could be more frequent than previously anticipated; however, we do not expect these antagonistic interactions to affect the establishment of either agent.

Formulation and characterization of garlic (Allium sativum L.) essential oil nanoemulsion and its acaricidal activity on eriophyid olive mites (Acari: Eriophyidae)

Green and nanoacaricides including essential oil (EO) nanoemulsions are important compounds to provide new, active, safe acaricides and lead to improvement of avoiding the risk of synthetic acaricides. This study was carried out for the first time on eriophyid mites to develop nanoemulsion of garlic essential oil by ultrasonic emulsification and evaluate its acaricidal activity against the two eriophyid olive mites Aceria oleae Nalepa and Tegolophus hassani (Keifer). Acute toxicity of nanoemulsion was also studied on male rats. Garlic EO was analyzed by gas chromatography-mass spectrometry (GC-MS), and the major compounds were diallyl sulfide (8.6%), diallyl disulfide (28.36%), dimethyl tetrasulfide (15.26%), trisulfide,di-2-propenyl (10.41%), and tetrasulfide,di-2-propenyl (9.67%). Garlic oil nanoemulsion with droplet size 93.4 nm was formulated by ultrasonic emulsification for 35 min. Emulsification time and oil and surfactant ratio correlated to the emulsion droplet size and stability. The formulated nanoemulsion showed high acaricidal activity against injurious eriophyid mites with LC₅₀ 298.225 and 309.634 μg/ml, respectively. No signs of nanoemulsion toxicity were noted in treating rats; thus, it may be considered non-toxic to mammals. Stability of garlic oil nanoemulsion, high acaricidal activity, and the absence of organic toxic solvents make the formulation that may be a possible acaricidal product. Results suggest the possibility of developing suitable natural nanoacaricide from garlic oil.

Phenetic and phylogenetic relationships among Aceria spp. (Acari: Eriophyoidea) inhabiting species within the family Brassicaceae in Serbia

We examined morphological and genetic differences among Aceria spp. inhabiting six Brassicaceae species in Serbia. Five of them have been already mentioned in the literature as original or alternate hosts of Aceria spp. (Berteroa incana (L.) DC., Capsella bursa-pastoris (L.) Medik., Cardamine hirsuta L., Lepidium draba L. and Sisymbrium orientale L.), whereas Aurinia petraea (Ard.) Schur was registered here for the first time as a host for Aceria sp. Results of morphometric analyses indicated clear differentiation of Aceria spp. from B. incana, L. draba, A. petraea and S. orientale, whereas the other two entities were less diverse and clustered together. Molecular analyses indicated that the average mean divergence over all sequence pairs was 18.3% (11.8-25.9%) and disclosed that the observed mtCOI distances between the six host-associated Aceria entities are large enough to represent differences between species. The Aceria sp. hosted by B. incana was morphologically and genetically most distinctive, whereas discrepancy between phenetic and phylogenetic relationships was found in the position of Aceria sp. hosted by L. draba when compared with those inhabiting C. hirsuta, S. orientale and C. bursa-pastoris.

What Azure blues occur in Canada? A re-assessment of Celastrina Tutt species (Lepidoptera, Lycaenidae)

The identity of Celastrina species in eastern Canada is reviewed based on larval host plants, phenology, adult phenotypes, mtDNA barcodes and re-assessment of published data. The status of the Cherry Gall Azure (Celastrinaserotina Pavulaan & Wright) as a distinct species in Canada is not supported by any dataset, and is removed from the Canadian fauna. Previous records of this taxon are re-identified as Celastrinalucia (Kirby) and Celastrinaneglecta (Edwards). Evidence is presented that both Celastrinalucia and Celastrinaneglecta have a second, summer-flying generation in parts of Canada. The summer generation of Celastrinalucia has previously been misidentified as Celastrinaneglecta, which differs in phenology, adult phenotype and larval hosts from summer Celastrinalucia. DNA barcodes are highly conserved among at least three North American Celastrina species, and provide no taxonomic information. Celastrinaneglecta has a Canadian distribution restricted to southern Ontario, Manitoba, Saskatchewan and easternmost Alberta. The discovery of museum specimens of Celastrinaladon (Cramer) from southernmost Ontario represents a new species for the Canadian butterfly fauna, which is in need of conservation status assessment.