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Two-spotted spider mite (Tetranychus urticae) is an important greenhouse pest. In cucumbers, heavy infestations lead to the complete loss of leaf assimilation surface, resulting in plant death. Symptoms caused by spider mite feeding alter the light reflection of leaves and could therefore be optically detected. Machine learning methods have already been employed to analyze spectral information in order to differentiate between healthy and spider mite-infested leaves of crops such as tomatoes or cotton. In this study, machine learning methods were applied to cucumbers. Hyperspectral data of leaves were recorded under controlled conditions. Effective wavelengths were identified using three feature selection methods. Subsequently, three supervised machine learning algorithms were used to classify healthy and spider mite-infested leaves. All combinations of feature selection and classification methods yielded accuracy of over 80%, even when using ten or five wavelengths. These results suggest that machine learning methods are a powerful tool for image-based detection of spider mites in cucumbers. In addition, due to the limited number of wavelengths, there is also substantial potential for practical application., (© 2024. The Author(s).)

In this work we reported injuries caused by the spider mite Oligonychus yothersi on Vitis vinifera leaves and we also investigate the sex ratio of this species under laboratory conditions. To access the aspects regarding reproduction, females were placed individually in arenas made of V. vinifera leaves to oviposit and all progeny were mounted on slides when they reached adulthood to confirm the offspring sex. Our study showed that O. yothersi reproduces by thelytokous /arrhenotokous parthenogenesis, generating low number of males. Additionally, we found vine plants with leaf browning, particularly on the adaxial surface, where mites were usually found.

Based on morphological and molecular evidence, Eotetranychus asiaticus Ehara is confirmed as a junior synonym of E. sexmaculatus (Riley). Eotetranychus queenslandicus Manson differs to E. sexmaculatus in some morphological characters states, and currently there is insufficient evidence to confirm if it is also a junior synonym. We therefore propose that it remains a valid species until fresh material can be collected from the type host (Codiaeum variegatum (L.) A.Juss.; Euphorbiaceae) in the type location (Freshwater, Queensland, Australia) for molecular analysis and further comparisons. Eotetranychus sexmaculatus is confirmed as present in Australia and New Zealand. Our analyses indicate that specimens identified as E. sexmaculatus from avocado (Persea americana Mill.; Lauraceae) in Western Australia and New Zealand, and specimens of E. asiaticus from the type host (Ficus erecta Thunb.; Moraceae) and type location (Tomigusuku, Okinawa, Japan) are conspecific with specimens of E. sexmaculatus recently collected from the type host (Citrus sp.; Rutaceae) and type location (Florida, USA), with 0-3.6% divergence in a fragment (451 bp) of cytochrome oxidase subunit I (COI), and 0-0.3% in the ribosomal internal transcribed spacer II (ITS2) gene. Herein we redefine E. sexmaculatus, providing a revised diagnosis, notes on leg chaetotaxy, and variation in the shape of the aedeagus-which is a keystone feature critical for determining species boundaries of spider mite species that have males. Our findings also reinforce the potential of the eupathidion on the palptarsus suζ (i.e. the spinneret) for species diagnoses.

Plant-herbivore interactions promote the generation and maintenance of both plant and herbivore biodiversity. The antagonistic interactions between plants and herbivores lead to host race formation: the evolution of herbivore types specializing on different plant species, with restricted gene flow between them. Understanding how ecological specialization promotes host race formation usually depends on artificial approaches, using laboratory experiments on populations associated with agricultural crops. However, evidence on how host races are formed and maintained in a natural setting remains scarce. Here, we take a multidisciplinary approach to understand whether populations of the generalist spider mite Tetranychus urticae form host races in nature. We demonstrate that a host race co-occurs among generalist conspecifics in the dune ecosystem of The Netherlands. Extensive field sampling and genotyping of individuals over three consecutive years showed a clear pattern of host associations. Genome-wide differences between the host race and generalist conspecifics were found using a dense set of SNPs on field-derived iso-female lines and previously sequenced genomes of T. urticae. Hybridization between lines of the host race and sympatric generalist lines is restricted by post-zygotic breakdown, and selection negatively impacts the survival of generalists on the native host of the host race. Our description of a host race among conspecifics with a larger diet breadth shows how ecological and reproductive isolation aid in maintaining intra-specific variation in sympatry, despite the opportunity for homogenization through gene flow. Our findings highlight the importance of explicitly considering the spatial and temporal scale on which plant-herbivore interactions occur in order to identify herbivore populations associated with different plant species in nature. This system can be used to study the underlying genetic architecture and mechanisms that facilitate the use of a large range of host plant taxa by extreme generalist herbivores. In addition, it offers the chance to investigate the prevalence and mechanisms of ecological specialization in nature., (© 2021. The Author(s).)

Background: Attributes of pest species like host range are frequently reported as being evolutionarily constrained and showing phylogenetic signal. Because these attributes in turn could influence the abundance and impact of species, phylogenetic information could be useful in predicting the likely status of pests. In this study, we used regional (China) and global datasets to investigate phylogenetic patterns in occurrence patterns and host ranges of spider mites, which constitute a pest group of many cropping systems worldwide., Results: We found significant phylogenetic signal in relative abundance and distribution range both at the regional and global scales. Relative abundance and range size of spider mites were positively correlated with host range, although these correlations became weaker after controlling for phylogeny., Conclusions: The results suggest that pest impacts are evolutionarily constrained. Information that is easily obtainable - including the number of known hosts and phylogenetic position of the mites - could therefore be useful in predicting future pest risk of species.

Tetranychus pueraricola is a newly reported spider mite that occurs frequently in mainland China. It is possible that this species was introduced from elsewhere and became a serious pest recently. However, the correct identification of red-pigmented spider mites has repeatedly proven problematic. There is also the possibility that T. pueraricola in China was long misidentified as its sibling species, Tetranychus urticae (red form). To test which of these two scenarios is the more likely, individuals from 14 populations of T. pueraricola and five populations of T. urticae (red form) in China were sampled and genotyped using mitochondrial COI and microsatellite loci. Unlike a recent invasive species, the genetic diversity of T. pueraricola was very high with high mitochondrial genetic diversity (16 haplotypes), high effective alleles (Ne = 2.038 ± 0.081) and expected heterozygosity (He = 0.395 ± 0.016). Surprisingly, we found that all T. urticae (red form) populations shared only one mitochondrial haplotype and showed quite low genetic diversity (Ne = 1.443 ± 0.055; He = 0.234 ± 0.025) which was even lower than that of the green form of T. urticae in mainland China from a previous study. We did not detect significant signals of recent bottlenecks for most populations from both species. These results suggest T. pueraricola is unlikely to be a recent invasive pest but a species that has existed in China for a long time. It is probable that T. pueraricola in China has long been misidentified as T. urticae (red form).

Spider mites of the genus Tetranychidae are severe crop pests. In the Mediterranean a few species coexist, but they are difficult to identify based on morphological characters. Additionally, spider mites often harbour several species of endosymbiotic bacteria, which may affect the biology of their hosts. Here, we propose novel, cost-effective, multiplex diagnostic methods allowing a quick identification of spider-mite species as well as of the endosymbionts they carry. First, we developed, and successfully multiplexed in a single PCR, primers to identify Tetranychus urticae, T. evansi and T. ludeni, some of the most common tetranychids found in southwest Europe. Moreover, we demonstrated that this method allows detecting multiple species in a single pool, even at low frequencies (up to 1/100), and can be used on entire mites without DNA extraction. Second, we developed another set of primers to detect spider-mite endosymbionts, namely Wolbachia, Cardinium and Rickettsia in a multiplex PCR, along with a generalist spider-mite primer to control for potential failure of DNA amplification in each PCR. Overall, our method represents a simple, cost-effective and reliable method to identify spider-mite species and their symbionts in natural field populations, as well as to detect contaminations in laboratory rearings. This method may easily be extended to other species.

Despite the ubiquity of coinfection, we know little of the effects of intra-specific genetic variability on coinfection by distinct parasite species. Here we test the hypothesis that parasite multiplication depends on the combination of parasite genotypes that coinfect the host (that is Genotype. parasite × Genotype .parasite interaction). To that aim, we infected tomato leaves with the ecto-parasitic mites Tetranychus urticae and Tetranychus evansi. We tested all possible combinations between four T. urticae and two T. evansi populations sampled on different hosts or localities. There was no universal (that is genotype-independent) effect of coinfection on mite multiplication; in many cases the two species had no effect on each other. However, several combinations of T. evansi and T. urticae populations led to elevated T. evansi numbers. Similarly, T. urticae reproduction largely depended on the interaction between T. urticae and T. evansi populations. This evidence for genotype-by-genotype interaction between coinfecting parasites indicates that the effect of coinfection on parasite epidemiology and evolution may vary in space according to the genetic composition of local parasite populations; it further suggests the possibility of coevolution between parasites species that share the same hosts.

The evolution of resource use in herbivores has been conceptualized as an analog of the theory of island biogeography, assuming that plant species are islands separated by phylogenetic distances. Despite its usefulness, this analogy has paradoxically led to neglecting real biogeographical processes in the study of macroevolutionary patterns of herbivore-plant interactions. Here we show that host use is mostly determined by the geographical cooccurrence of hosts and parasites in spider mites (Tetranychidae), a globally distributed group of plant parasites. Strikingly, geography accounts for most of the phylogenetic signal in host use by these parasites. Beyond geography, only evolutionary transitions among major plant lineages (i.e., gymnosperms, commelinids, and eudicots) shape resource use patterns in these herbivores. Still, even these barriers have been repeatedly overcome in evolutionary time, resulting in phylogenetically diverse parasite communities feeding on similar hosts. Therefore, our results imply that patterns of apparent evolutionary conservatism may largely be a byproduct of the geographic cooccurrence of hosts and parasites., Competing Interests: The authors declare no conflict of interest.

Reproductive endosymbionts have been shown to have wide-ranging effects on many aspects of their hosts' biology. A first step to understanding how these endosymbionts interact with their hosts is to determine their incidences. Here, we screened for four reproductive endosymbionts (Wolbachia, Cardinium, Spiroplasma and Rickettsia) in 28 populations of spider mites (Acari: Tetranychidae) representing 12 species. Each of the four endosymbionts were identified in at least some of the tested specimens, and their infection patterns showed variations at the species-level and population-level, suggesting their distributions can be correlated with both the phylogeny and ecology of the hosts. Co-infections of unrelated bacteria, especially double infections of Wolbachia and Cardinium within the same individuals were common. Spiroplasma and Rickettsia infections were specific to particular host species, respectively. Further, the evolutionary histories of these endosymbionts were inferred by comparing the phylogenies of them and their hosts. These findings can help to clarify the interactions between endosymbionts and arthropods.

A survey of Panonychus species was undertaken across Georgia from 2005 to 2014 on various host plants, revealing three species: Panonychus citri (McGregor, 1916), Panonychus hadzhibejliae (Reck, 1947) and Panonychus ulmi (Koch, 1836). New hosts for P. ulmi and P. citri are recorded, Buxus sempervirens, Hedera colchica and Prunus laurocerasus for P. ulmi and Ficus carica for P. citri, whereas P. hadzhibejliae was only found on F. carica. The newly collected material also allowed us to investigate the taxonomical status of P. hadzhibejliae. The comparison of P. hadzhibejliae with the two closely related species sampled in the survey, P. ulmi and P. citri, and with data of P. caricae found in the literature, shows that P. hadzhibejliae is a valid species. It can be separated from the three other Panonychus species without ambiguity especially using the female dorsal setae length in combination with the ratio between the length of the female dorsal opisthosomal f 2 and h 1 setae and the ratio between the palptarsal terminal eupathidium su and the related solenidion ω. A redescription of P. hadzhibejliae is provided including the male and some morphological characters, measurements and drawings of the female that were omitted in the original description. A key to the world species of Panonychus is also proposed.

Two species of Tetranychidae (Acari), Oligonychus neotylus sp. nov. from Zea mays and Pennisetum purpureum (Poaceae) and Tetranychus hirsutus sp. nov. from Gymnema sylvestre R. Br. (Apocynaceae) are described from Karnataka state, south India. Tetranychus bambusae Wang and Ma is recorded for the first time from India and re-described. Four other species are reported for the first time from India viz., Oligonychus coniferarum (McGregor), Oligonychus duncombei Meyer, Tetranychus marianae McGregor and Tetranychus okinawanus Ehara from Cupressus sp., an undetermined grass, Centrosema pubescens and Adenium obesum, respectively.

Background: Tetranychus urticae is a highly polyphagous species with a cosmopolitan distribution that has the status of pest in more than 100 economically significant crops all over the world. Despite a number of previous efforts to isolate genetic markers, only a reduced set of microsatellite loci has been published. Taking advantage of the whole genome sequence of T. urticae that recently became available; we isolated and characterized a new set of microsatellite loci and tested the level of polymorphism across populations originating from a wide geographical area., Results: A total of 42 microsatellite sequences widespread in the T. urticae genome were identified, the exact position in the genome recorded, and PCR amplification of microsatellite loci tested with primers defined here. Fourteen loci showed unambiguous genotype patterns and were further characterized. Three multiplex polymerase chain reaction sets were optimized in order to genotype a total of 24 polymorphic loci, including 10 previously published Tetranychus-specific loci. The microsatellite kits successfully amplified 686 individuals from 60 field populations for which we assessed the level of genetic diversity. The number of alleles per locus ranged from 3 to 16 and the expected heterozygosity values ranged from 0.12 to 0.81. Most of the loci displayed a significant excess of homozygous and did not model the Hardy-Weinberg equilibrium. This can be explained by the arrhenotokous mode of reproduction of T. urticae., Conclusions: These primers represent a valuable resource for robust studies on the genetic structure, dispersal and population biology of T. urticae, that can be used in managing this destructive agricultural pest.

The production and uptake of yolk protein play an important role in the reproduction of all oviparous organisms. Vitellogenin (Vg) is the precursor of vitellin (Vn), which is the major egg storage protein, and vitellogenin receptor (VgR) is a necessary protein for the uptake of Vg into developing oocytes. In this paper, we characterize the full-length Vg and VgR, PcVg1 and PcVgR, respectively, of the citrus red mite Panonychus citri (McGregor). The PcVg1 cDNA is 5748 nucleotides (nt) with a 5553-nt open reading frame (ORF) coding for 1851 amino acids (aa), and the PcVgR is 6090 nt, containing an intact ORF of 5673 nt coding an expected protein of 1891 aa. The PcVg1 aa sequence shows a typical GLCG domain and several K/RXXR cleavage sites, and PcVgR comprises two ligand-binding domains, two epidermal growth factor (EGF)-like regions containing YWTD motifs, a transmembrane domain, and a cytoplasmic domain. An analysis of the aa sequences and phylogenetics implied that both genes were genetically distinct from those of ticks and insects. The transcriptional profiles determined by real-time quantitative PCR in different developmental stages showed that both genes present the same expressional tendencies in eggs, larvae, nymphs, and adults. This suggested that the biosynthesis and uptake of PcVg occurs coordinately. The strong reproductive capacity of P. citri has been hypothesized as an important factor in its resistance; consequently, understanding the molecular mechanisms regulating Vg and VgR are fundamental for mite control.

The carmine spider mite, Tetranychus cinnabarinus, which is also considered as the red form of Tetranychus urticae, is one of the most serious mite pests on crops. It is capable of rapidly developing resistance to acaricides, and has caused difficulty in controlling. However, the resistance mechanism of this mite remains unclear at molecular level. As a member of main detoxification enzymes, cytochrome P450 monooxygenases (CYPs or P450s) play important roles in the development of acaricide resistance in arthropods. In this study, two novel P450 genes (CYP389B1 and CYP392A26) were identified and characterized from T. cinnabarinus. The opening reading frames (ORFs) of CYP389B1 and CYP392A26 contained 1545 and 1488 nucleotides, which encode 514 and 495 amino acids, respectively. Phylogenetic analysis showed that CYP389B1 and CYP392A26 were most closely related to CYP389B1 and CYP392A4 from T. urticae, respectively. When treated with piperonyl butoxide (PBO), an inhibitor of P450s, the resistance ratio of fenpropathrin-resistant (FeR) strain decreased from 101- to 75-fold, which suggested a correlation between P450 and fenpropathrin-resistance in T. cinnabarinus. Furthermore, constitutive over-expressions of CYP389B1 and CYP392A26 were detected in FeR strain. Meanwhile, the expressions of CYP389B1 and CYP392A26 were inducible in FeR strain after treatment in 6, 12 and 24 h with LC30 of fenpropathrin; especially, the expression of CYP392A26 increased to a markedly high level (20.88-fold higher than in the control) after treatment in 6 h. However, there was no significant difference between treatment and control in susceptible strain. Furthermore, stage specific expression profiles of these two genes did not show significant difference among developing stages, except for eggs, in which the mRNA levels were quite low. The results indicate that CYP389B1 and CYP392A26 were involved in the fenpropathrin-resistance in T. cinnabarinus, and the expression of CYP392A26 was more sensitive to fenpropathrin stress. These findings provide clues for further elucidating the function and regulation mechanism of these two cytochrome P450 genes in T. cinnabarinus., (Copyright © 2015 Elsevier Inc. All rights reserved.)

When phylogenetically close, two competing species may reproductively interfere, and thereby affect their population dynamics. We tested for reproductive interference (RI) between two congeneric haplo-diploid spider mites, Tetranychus evansi and Tetranychus urticae, by investigating their interspecific mating and their population dynamics when they competed on the same plants. They are both pests of tomato, but differ in the host plant defences that they suppress or induce. To reduce the effect of plant-mediated interaction, we used a mutant tomato plant lacking jasmonate-mediated anti-herbivore defences in the competition experiment. In addition, to manipulate the effect of RI, we introduced founder females already mated with conspecific males in mild RI treatments or founder, virgin females in strong RI treatments (in either case together with heterospecific and conspecific males). As females show first-male sperm precedence, RI should occur especially in the founder generation under strong RI treatments. We found that T. urticae outcompeted T. evansi in mild, but not in strong RI treatments. Thus, T. evansi interfered reproductively with T. urticae. This result was supported by crossing experiments showing frequent interspecific copulations, strong postmating reproductive isolation and a preference of T. evansi males to mate with T. urticae (instead of conspecific) females, whereas T. urticae males preferred conspecific females. We conclude that interspecific mating comes at a cost due to asymmetric mate preferences of males. Because RI by T. evansi can improve its competitiveness to T. urticae, we propose that RI partly explains why T. evansi became invasive in Europe where T. urticae is endemic.