Functional responses of two species of predatory mites (Acari: Phytoseiidae) to eggs and first-instar nymphs of Bactericera Gobica Logniova (Homoptera: Psyllidae).

The goji berry psyllid, Bactericera gobica Logniova (Homoptera: Psyllidae), is one of the most important pests on goji berry plants (Lycium barbarum L.), whose fruits are widely used in traditional Chinese medicine and food. However, chemical control is still the predominant control strategy of this pest. Recently, two species of predatory mites, Neoseiulus setarius Ma, Meng & Fan and Neoseiulus barkeri Hughes were found to be associated with B. gobica in China. To assess their predation potential against B. gobica, the functional responses of these two phytoseiid species feeding on different densities (2, 4, 8, 12, 16, 24 and 32 individuals) of B. gobica eggs and 1st instar nymphs were compared at a temperature of 25ºC ± 1º C. Logistic regression analysis revealed that both predatory mite species exhibited type Holling-II functional responses on eggs and 1st instar nymphs of B. gobica, with the predation number increased for both predators as the density of prey increased. Overall, N. setarius consumed more prey compared to N. barkeri across all levels of prey densities. Meanwhile, the highest attack rate (α = 0.0283), the lowest handling time (Th = 1.1324 h prey- 1), and the highest estimated maximum predation rate (T/Th = 21.19 prey day- 1) were all observed for N. setarius fed with 1st instar nymphs of B. gobica. These findings suggest that it is worthy considering utilizing N. setarius and N. barkeri as candidate biocontrol agents of B. gobica, with N. setarius appearing to be a more effective predator than N. barkeri.

Psyllids in Natural Habitats as Alternative Resources for Key Natural Enemies of the Pear Psyllids (Hemiptera: Psylloidea).

The pear psyllids (Cacopsylla spp.; Psylloidea) comprise ~24 species of sap-feeding insects distributed in Europe, temperate Asia, and (as introductions) in the Americas. These pear-specialized insects are among the most damaging and difficult to control pests in orchards. Biological control increasingly is being used to replace or partially replace insecticidal management of pear psyllids. Many key natural enemies of pear psyllids regularly occur in non-orchard habitats on native plants. The presence of beneficial species both in orchard and non-orchard habitats (here referred to as "spillover") has prompted suggestions that native plants and their associated psyllids should be conserved as alternative resources for natural enemies of pear psyllids. The expectation is that the natural enemies will move from those habitats into psyllid-infested orchards. This review shows that psyllids in native habitats are important resources for several key predators and parasitoids of pear psyllids. These resources are critical enough that some beneficials exhibit an almost nomadic existence as they move between plant species, tracking the seasonal appearance and disappearance of psyllid species. In contrast, other natural enemies show minimal or no spillover between orchard and non-orchard habitats, which likely is evidence that they exhibit limited movement at best between orchard and non-orchard habitats. To show conclusively that spillover also indicates that a beneficial species disperses between native habitats and orchards requires difficult research on insect movement. This review concludes with a brief discussion of these difficulties and possible solutions.

Establishing reliable DNA barcoding primers for jumping plant lice (Psylloidea, Hemiptera).

OBJECTIVES: DNA Barcoding has proven to be a reliable method for rapid insect identification. The success of this method is based on the amplification of a specific region, the 'Folmer' barcode region at the 5´ start of the cytochrome c oxidase 1 gene (cox1), with universal primers. Previous studies showed failures of standard "universal" primers to amplify this region in psyllids. The aim of the study was the design of a new alternative more reliable primer combination for taxa of the superfamily Psylloidea and its comparison with the performance of the standard "universal" Folmer-primers. RESULTS: A newly designed degenerate forward primer LCOP-F was developed following comparison of the sequence alignment of the priming site of "universal" primer LCO1490 and the standard insect forward primer LepF1. When combined with the "universal" reverse primer, HCO2198, this new primer pairing was able to generate barcode sequence for all 36 species in 20 genera across the five families of psyllids tested in this study, and these primers were found to be more universally reliable across psyllid taxa than other primer pairs tested.

YOLO-SCL: a lightweight detection model for citrus psyllid based on spatial channel interaction.

Efficient and accurate detection and providing early warning for citrus psyllids is crucial as they are the primary vector of citrus huanglongbing. In this study, we created a dataset comprising images of citrus psyllids in natural environments and proposed a lightweight detection model based on the spatial channel interaction. First, the YOLO-SCL model was based on the YOLOv5s architecture, which uses an efficient channel attention module to perform local channel attention on the inputs in the recursive gated convolutional modules to achieve a combination of global spatial and local channel interactions, improving the model's ability to express the features of the critical regions of small targets. Second, the lightweight design of the 21st layer C3 module in the neck network of the YOLO-SCL model and the small target feature information were retained to the maximum extent by deleting the two convolutional layers, whereas the number of parameters was reduced to improve the detection accuracy of the model. Third, with the detection accuracy of the YOLO-SCL model as the objective function, the black widow optimization algorithm was used to optimize the hyperparameters of the YOLO-SCL model, and the iterative mechanism of swarm intelligence was used to further improve the model performance. The experimental results showed that the YOLO-SCL model achieved a mAP@0.5 of 97.07% for citrus psyllids, which was 1.18% higher than that achieved using conventional YOLOv5s model. Meanwhile, the number of parameters and computation amount of the YOLO-SCL model are 6.92 M and 15.5 GFlops, respectively, which are 14.25% and 2.52% lower than those of the conventional YOLOv5s model. In addition, after using the black widow optimization algorithm to optimize the hyperparameters, the mAP@0.5 of the YOLO-SCL model for citrus psyllid improved to 97.18%, making it more suitable for the natural environments in which citrus psyllids are to be detected. The experimental results showed that the YOLO-SCL model has good detection accuracy for citrus psyllids, and the model was ported to the Jetson AGX Xavier edge computing platform, with an average processing time of 38.8 ms for a single-frame image and a power consumption of 16.85 W. This study provides a new technological solution for the safety of citrus production.

Division of labor within psyllids: metagenomics reveals an ancient dual endosymbiosis with metabolic complementarity in the genus Cacopsylla.

IMPORTANCE: Heritable beneficial bacterial endosymbionts have been crucial for the evolutionary success of numerous insects by enabling the exploitation of nutritionally limited food sources. Herein, we describe a previously unknown dual endosymbiosis in the psyllid genus Cacopsylla, consisting of the primary endosymbiont "Candidatus Carsonella ruddii" and a co-occurring Enterobacteriaceae bacterium for which we propose the name "Candidatus Psyllophila symbiotica." Its localization within the bacteriome and its small genome size confirm that Psyllophila is a co-primary endosymbiont widespread within the genus Cacopsylla. Despite its highly eroded genome, Psyllophila perfectly complements the tryptophan biosynthesis pathway that is incomplete in the co-occurring Carsonella. Moreover, the genome of Psyllophila is almost as small as Carsonella's, suggesting an ancient dual endosymbiosis that has now reached a precarious stage where any additional gene loss would make the system collapse. Hence, our results shed light on the dynamic interactions of psyllids and their endosymbionts over evolutionary time.

Candidatus Liberibacter: From Movement, Host Responses, to Symptom Development of Citrus Huanglongbing.

Candidatus Liberibacter spp. are fastidious α-proteobacteria that cause multiple diseases on plant hosts of economic importance, including the most devastating citrus disease: Huanglongbing (HLB). HLB was reported in Asia a century ago but has since spread worldwide. Understanding the pathogenesis of Candidatus Liberibacter spp. remains challenging as they are yet to be cultured in artificial media and infect the phloem, a sophisticated environment that is difficult to manipulate. Despite those challenges, tremendous progress has been made on Ca. Liberibacter pathosystems. Here, we first reviewed recent studies on genetic information of flagellar and type IV pili biosynthesis, their expression profiles, and movement of Ca. Liberibacter spp. inside the plant and insect hosts. Next, we reviewed the transcriptomic, proteomic, and metabolomic studies of susceptible and tolerant plant genotypes to Ca. Liberibacter spp. infection and how Ca. Liberibacter spp. adapt in plants. Analyses of the interactions between plants and Ca. Liberibacter spp. imply the involvement of immune response in the Ca. Liberibacter pathosystems. Lastly, we reviewed how Ca. Liberibacter spp. movement inside and interactions with plants lead to symptom development.

The complete mitochondrial genome of Cacopsyllaburckhardti (Hemiptera, Psylloidea, Psyllidae).

Cacopsyllaburckhardti Luo, Li, Ma & Cai, 2012 (Hemiptera, Psylloidea, Psyllidae) is a pear psyllid species, distributed in the East Asia. The complete mitogenome of C.burckhardti is obtained in this study for the first time. The mitogenome of C.burckhardti is circular form and 14,798 bp long, which consists of 13 protein-coding genes, 22 tRNAs and two rRNAs. The base composition is 38.80% for A, 34.89% for T, 9.99% for G and 16.33% for C, with the higher A + T contents (73.69%). The phylogenetic analysis, using 13 protein-coding genes, shows that C.burckhardti is clustered with other Cacopsylla species and nested in the Psyllidae clade within the superfamily Psylloidea.

First systematic inventory of the jumping plant lice of Luxembourg (Hemiptera, Sternorrhyncha, Psylloidea).

Psyllids (superfamily Psylloidea), also known as jumping plant lice, are a group of plant-sap sucking Hemiptera having significant pest status for crops, forest trees and ornamental plants. Only seven species of psyllids have been recorded in Luxembourg so far. An additional group of seven species has been recorded exclusively, based on the findings of their galls or specific plant deformations; but no mention exists in literature on the actual collection of the inducing insect in Luxembourg. To fill this knowledge gap, field collections were carried out during the years 2019-2020. In addition, samples from 1999-2000 stored in the wet collection of the Musée National d'Histoire Naturelle de Luxembourg were studied. This research, in combination with information coming from literature, allowed us to list 48 species of the families Aphalaridae (5 species), Liviidae (5), Psyllidae (24) and Triozidae (14), though the presence of one species within the last family (Triozarhamni) needs to be confirmed. Brief information on geographical distribution, biology and (if available) illustrations of diagnostic characters are provided on the psyllid species detected in Luxembourg so far.

Density thresholds and the incorporation of biocontrol into decision-making to enhance the control of Cacopsylla pyri in pear (cv. Ercolini) orchards.

BACKGROUND: Economic injury level (EIL) and economic threshold (ET) are customary tools for integrated pest management. Cacopsylla pyri L. is a major pest in pear orchards. The aim of this work was to establish EIL and ET for the optimization of the use of insecticides to control this psyllid, considering biocontrol and two spraying strategies (low-toxicity versus broad spectrum chemicals). This research was conducted over 4 years in five commercial pear, cv. Ercolini, orchards in south-eastern Spain. RESULTS: Psyllids and ant populations were followed using periodic sampling, and the russet on fruits was quantified. The effect of spray intensity and ant exclusion on psyllid abundance and yield were also tested: both had a significant effect on the cumulative number of C. pyri (CNP), yield and fruit weight. Yield was found to be negatively correlated with CNP. The russet index (RI) increased in a sigmoidal fashion as a function of CNP, being significantly higher with than without ant exclusion. The commercial categorization of fruits was explained satisfactorily as a function of CNP and the cumulative number of ants (CNA). The quantitative EIL was established at a CNP of 427.2 for spraying with paraffinic oil and 425.7 for abamectin. As for the cosmetic EIL, when CNA was zero, this EIL was 24.2, at a CNP of 16.6 for spraying with paraffinic oil or abamectin. CONCLUSIONS: The use of products of low toxicity, for the conservation of ants, is expected to increase ET and, thus, reduce the intensity of spraying. © 2021 Society of Chemical Industry.

Potato Zebra Chip: An Overview of the Disease, Control Strategies, and Prospects.

Potato (Solanum tuberosum L.) is an important food crop worldwide. As the demand for fresh and processed potato products is increasing globally, there is a need to manage and control devastating diseases such as zebra chip (ZC). ZC disease causes major yield losses in many potato-growing regions and is associated with the fastidious, phloem-limited bacterium Candidatus Liberibacter solanacearum (CLso) that is vectored by the potato-tomato psyllid (Bactericera cockerelli Sulc). Current management measures for ZC disease mainly focus on chemical control and integrated pest management strategies of the psyllid vector to limit the spread of CLso, however, they add to the costs of potato production. Identification and deployment of CLso and/or the psyllid resistant cultivars, in combination with integrated pest management, may provide a sustainable long-term strategy to control ZC. In this review, we provide a brief overview of the ZC disease, epidemiology, current management strategies, and potential new approaches to manage ZC disease in the future.

Introduction to the study of chromosomal and reproductive patterns in Paraneoptera.

This paper opens the themed issue (a monograph) "Aberrant cytogenetic and reproductive patterns in the evolution of Paraneoptera", prepared by a Russian-Bulgarian research team on the basis of long-term collaborative studies. In this first part of the issue, we provide the basic introductory information, describe the material involved and the methods applied, and give terminology and nomenclature of used taxonomic names.

The transcriptome landscapes of citrus leaf in different developmental stages.

KEY MESSAGE: The temporal expression profiles of citrus leaves explain the sink-source transition of immature leaves to mature leaves and provide knowledge regarding the differential responses of mature and immature leaves to biotic stress such as citrus canker and Asian citrus psyllid (Diaphorina citri). Citrus is an important fruit crop worldwide. Different developmental stages of citrus leaves are associated with distinct features, such as differences in susceptibilities to pathogens and insects, as well as photosynthetic capacity. Here, we investigated the mechanisms underlying these distinctions by comparing the gene expression profiles of mature and immature citrus leaves. Immature (stages V3 and V4), transition (stage V5), and mature (stage V6) Citrus sinensis leaves were chosen for RNA-seq analyses. Carbohydrate biosynthesis, photosynthesis, starch biosynthesis, and disaccharide metabolic processes were enriched among the upregulated differentially expressed genes (DEGs) in the V5 and V6 stages compared with that in the V3 and V4 stages. Glucose level was found to be higher in V5 and V6 than in V3 and V4. Among the four stages, the largest number of DEGs between contiguous stages were identified between V5 and V4, consistent with a change from sink to source, as well as with the sucrose and starch quantification data. The differential expression profiles related to cell wall synthesis, secondary metabolites such as flavonoids and terpenoids, amino acid biosynthesis, and immunity between immature and mature leaves may contribute to their different responses to Asian citrus psyllid infestation. The expression data suggested that both the constitutive and induced gene expression of immunity-related genes plays important roles in the greater resistance of mature leaves against Xanthomonas citri compared with immature leaves. The gene expression profiles in the different stages can help identify stage-specific promoters for the manipulation of the expression of citrus traits according to the stage. The temporal expression profiles explain the sink-source transition of immature leaves to mature leaves and provide knowledge regarding the differential responses to biotic stress.

Queiroziella gen. nov., a new genus of jumping plant-lice (Hemiptera, Psyllidae) from Southern Brazil associated with Mimosa scabrella (Leguminosae).

Queiroziella gen. nov., a new genus of Psylloidea (Psyllidae, Ciriacreminae), is erected for five new species developing on the multipurpose tree Mimosa scabrella (Leguminosae, Caesalpinioideae, mimosoid clade): viz. Queiroziella erato sp. nov., Q. euterpe sp. nov., Q. melpomone sp. nov., Q. terpsichore sp. nov. and Q. thalia sp. nov. Another species from Paraguay, associated with an unidentified Mimosa species, is transferred to the new genus as Queiroziella borealis (Burckhardt, 1987), comb. nov., from Zonopelma (Aphalaroidinae). The new taxa are diagnosed, described and illustrated, and keys are provided for the identification of adults and immatures. Morphologically, Queiroziella resembles Heteropsylla which is also associated with mimosoid legumes and with which it may be closely related. As their host, the new species are restricted to Southern Brazil. Queiroziella euterpe, Q. melpomone and Q. terpsichore are reported from the states of Paraná, Rio Grande do Sul, Santa Catarina and São Paulo, Q. thalia from Paraná and São Paulo, and Q. erato from Paraná. No clear phenological patterns were found though it seems that high psyllid populations coincide with new flush of the host plants. Despite that the psyllids occur sometimes in very high numbers, no visible damage could be detected on host trees. On the other hand, the honeydew of the psyllids may provide a food source for honey-bees during non-flowering periods of Mimosa scabrella.

Assessment of the biocontrol potential of natural enemies against psyllid populations in a pear tree orchard during spring.

BACKGROUND: Modern pest control management systems are based on the support of naturally occurring arthropod predators, as it has been shown that such predators offer an important ecosystem service. However, most naturally occurring arthropod predators are generalists (euryphagous). Their role in the biological control of specific pests has been recognized but remains poorly studied. Here, we focused on the naturally occurring arthropod predators of psyllids - the main insect pest of pear trees. We investigated the abundance of psyllids and all of their potential enemies in an abandoned pear orchard on a weekly basis from early spring to early summer. In addition, employing polymerase chain reaction diagnostics and specific primers, we investigated the predation rate on psyllids in all predators collected. RESULTS: We found four predatory groups: spiders were the most abundant (60%, N = 756), followed by coccinellid beetles, anthocorid bugs and cantharid beetles. Anthocorids and spiders had the highest predation rates among the predatory groups. Among spiders, >50% of foliage-dwelling spiders (belonging to the genera Philodromus and Clubiona; N = 206) were positive for psyllids and showed a numerical response to the abundance of psyllids. CONCLUSION: We conclude that foliage-dwelling spiders are, of the four groups, the most important natural enemies of psyllids on pear trees during spring in Central Europe, as they outnumber specialized Anthocoris bugs. © 2021 Society of Chemical Industry.

Detection Method of Citrus Psyllids With Field High-Definition Camera Based on Improved Cascade Region-Based Convolution Neural Networks.

Citrus psyllid is the only insect vector of citrus Huanglongbing (HLB), which is the most destructive disease in the citrus industry. There is no effective treatment for HLB, so detecting citrus psyllids as soon as possible is the key prevention measure for citrus HLB. It is time-consuming and laborious to search for citrus psyllids through artificial patrol, which is inconvenient for the management of citrus orchards. With the development of artificial intelligence technology, a computer vision method instead of the artificial patrol can be adopted for orchard management to reduce the cost and time. The citrus psyllid is small in shape and gray in color, similar to the stem, stump, and withered part of the leaves, leading to difficulty for the traditional target detection algorithm to achieve a good recognition effect. In this work, in order to make the model have good generalization ability under outdoor light condition, a high-definition camera to collect data set of citrus psyllids and citrus fruit flies under natural light condition was used, a method to increase the number of small target pests in citrus based on semantic segmentation algorithm was proposed, and the cascade region-based convolution neural networks (R-CNN) (convolutional neural network) algorithm was improved to enhance the recognition effect of small target pests using multiscale training, combining CBAM attention mechanism with high-resolution feature retention network high-resoultion network (HRNet) as feature extraction network, adding sawtooth atrous spatial pyramid pooling (ASPP) structure to fully extract high-resolution features from different scales, and adding feature pyramid networks (FPN) structure for feature fusion at different scales. To mine difficult samples more deeply, an online hard sample mining strategy was adopted in the process of model sampling. The results show that the improved cascade R-CNN algorithm after training has an average recognition accuracy of 88.78% for citrus psyllids. Compared with VGG16, ResNet50, and other common networks, the improved small target recognition algorithm obtains the highest recognition performance. Experimental results also show that the improved cascade R-CNN algorithm not only performs well in citrus psylla identification but also in other small targets such as citrus fruit flies, which makes it possible and feasible to detect small target pests with a field high-definition camera.

Vertical Distribution of Insect Pests Using Insect Towers Placed Near Potato Fields in the Lower Columbia Basin.

This study was conducted at the Oregon State University Hermiston Agricultural Research and Extension Center, Hermiston, Umatilla County, OR, during the 2016 and 2017 potato, Solanum tuberosum L. (Solanales: Solanaceae), growing seasons. The objective was to determine the vertical distribution of hemipteran (Bactericera cockerelli Sulc, Circulifer tenellus Baker, Myzus persicae Sulzer, Macrosiphum euphorbiae Thomas, and Lygus spp.) and thysanopteran (Frankliniella occidentalis Pergande and Thrips tabaci Lindeman) potato pests using insect towers placed near potato fields. Towers were 8 m tall and secured to the ground with metal cables. In each tower, yellow sticky cards were mounted at 1.5 m intervals up to 7.6 m aboveground. Data were collected at 7-d intervals from mid-April until mid or end of August. This study showed that B. cockerelli, C. tenellus, M. persicae, Lygus spp., and both species of thrips were captured on sticky cards placed closest to the ground; in both years, as sticky card height increased, abundances decreased. In contrast, trapped M. euphorbiae numbers were not affected by sticky card height. To our knowledge, this is the first study in the lower Columbia Basin of Oregon that evaluated the vertical distribution of major potato pests.

Taxonomy and host-plant relationships of the psyllid genus Mitrapsylla (Hemiptera: Psylloidea: Psyllidae) in Brazil.

The Brazilian species of Mitrapsylla, a Neotropical genus of jumping plant-lice, are reviewed. Twenty-seven species are described as new, and one species originally described from Panama is recorded for the first time from Brazil. This brings the number of Brazilian species from 12 to 40 and for the Neotropical region to 51. The new species are illustrated and Mitrapsylla ceplaciensis (White Hodkinson), M. cubana Crawford and M. itaparica (Crawford) are redescribed. A key for the identification of males is provided for the Brazilian species and information is given on host-plants, habitat and distribution. Host-plants, all Leguminosae, are confirmed for 15 of the new species. The genus is predominantly tropical but extends into the subtropical states in South Brazil.

Metabolic Profiling of Hybrids Generated from Pummelo and Citrus latipes in Relation to Their Attraction to Diaphorina citri, the Vector of Huanglongbing.

The citrus industry at present is severely affected by huanglongbing disease (HLB). HLB is caused by the supposed bacterial pathogen "Candidatus Liberibacter asiaticus" and is transmitted by the insect vector, the Asian citrus psyllid, Diaphorina citri Kuwayama. Developing new citrus hybrids to improve HLB management is much needed. In this study, we investigated the metabolomic profiles of three new hybrids produced from the cross of C2-5-12 Pummelo (Citrus maxima (L.) Osbeck) × pollen from Citrus latipes. The hybrids were selected based on leaf morphology and seedling vigor. The selected hybrids exhibited compact and upright tree architecture as seen in C. latipes. Hybrids were verified by simple sequence repeat markers, and were subjected to metabolomic analysis using gas chromatography-mass spectrometry. The volatile organic compounds (VOCs) and polar metabolites profiling also showed that the new hybrids were different from their parents. Interestingly, the levels of stored VOCs in hybrid II were higher than those observed in its parents and other hybrids. The level of most VOCs released by hybrid II was also higher than that released from its parents. Additionally, the preference assay showed that hybrid II was more attractive to D. citri than its parents and other hybrids. The leaf morphology, compact and upright architecture of hybrid II, and its attraction to D. citri suggest that it could be used as a windbreak and trap tree for D. citri (double duty), once its tolerance to HLB disease is confirmed. Our results showed that metabolomic analysis could be successfully used to understand the biochemical mechanisms controlling the interaction of D. citri with its host plants.

Homologous series by Nikolai Vavilov in the phylogeny of Homoptera.

The paper briefly discusses the most impressive examples of the Nikolai Vavilov's "Law of homologous series" in the evolution of one of the largest animal groups, homopterous insects, which comprise about 65,000 recent species in the world fauna. Different taxonomic and phylogenetic characters (morpho-anatomical, cytogenetic, reproductive and others) are considered at the taxonomic ranks of the order, suborder, superfamily and family.

Jumping plant lice of the genus Aphalara (Hemiptera, Psylloidea, Aphalaridae) in the Neotropics.

The Neotropical species of the predominantly north temperate genus Aphalara are reviewed. Four species are recorded here from this region, two of which are described as new. Aphalara ritteri sp. nov. occurs in southern Brazil (Paraná, Rio Grande do Sul, Santa Catarina) and represents the first and only species reported from South America. A second new species, Aphalara ortegae sp. nov., is described from Mexico and Puerto Rico. Another two species, Aphalara persicaria Caldwell, 1937 and A. similaCaldwell, 1937, have been previously reported from Mexico and the USA, and one of them also from Cuba. The two new species are both associated with Persicaria hydropiperoides and P. punctata (Polygonaceae) on which the immatures induce leaf roll galls. The two new species are morphologically similar to A. persicaria, to which they are probably closely related. A key is provided for the adults and immatures of the Neotropical species of Aphalara.