Superfamily Psylloidea Research Articles

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

ObjectivesDNA 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.ResultsA 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.

The Hidden Secrets of Psylloidea: Biology, Behavior, Symbionts, and Ecology.

Psyllids constitute a diverse group of sap-feeding Sternorrhyncha that were relatively obscure until it was discovered that a handful of species transmit bacterial plant pathogens. Yet the superfamily Psylloidea is much richer than the sum of its crop-associated vectors, with over 4,000 described species exhibiting diverse life histories and host exploitation strategies. A growing body of research is uncovering fascinating insights into psyllid evolution, biology, behavior, and species interactions. This work has revealed commonalities and differences with better-studied Sternorrhyncha, as well as unique evolutionary patterns of lineage divergence and host use. We are also learning how psyllid evolution and foraging ecology underlie life history traits and the roles of psyllids in communities. At finer scales, we are untangling the web of symbionts across the psyllid family tree, linking symbiont and psyllid lineages, and revealing mechanisms underlying reciprocal exchange between symbiont and host. In this review, we synthesize and summarize key advances within these areas with a focus on free-living (nongalling) Psylloidea.

Genome-scale approach to reconstructing the phylogenetic tree of psyllids (superfamily Psylloidea) with account of systematic bias

Psyllids (class Insecta: order Hemiptera: superfamily Psylloidea) are a taxonomically and phylogenetically challenging clade. Recent studies have largely advanced the phylogeny of this group, yet the family-level relationships among Aphalaridae, Carsidaridae, and others remain unresolved. Genome-scale phylogenetic analysis is known to provide a finer resolution for problems like that. However, such phylogenomics also introduces new problems: incorrect trees with high confidence yielded due to systematic error (bias). Here we addressed these issues using hundreds of single-copy orthologous (SCO) genes in psyllid transcriptomes and genomes. Our analyses revealed conflicts between the nucleotide-based and amino-acid-based phylogenetic trees. While the nucleotide-based phylogeny strongly supported the (Aphalaridae + Carsidaridae) + Others relationship, the amino-acid-based one recovered Aphalaridae + (Carsidaridae + Others) with 100% support. Further inspection revealed significant compositional heterogeneity in nucleotide sequences for 67% of SCO genes, but not in the corresponding translated amino acid sequences. We then used different strategies to combat this compositional bias, and found that using the RY-coding strategy (coding the standard nucleotides as purines and pyrimidines) the nucleotide-based phylogeny became consistent with the amino-acid-based one. We further applied RY-coding to a published concatenated nucleotide dataset and recovered the Aphalaridae monophyly (which is refuted by the original literature on non-recoded sequences) at the base of psyllid tree. Moreover, it was found that variations in evolutionary rate could lead to errors in nucleotide-based phylogeny. The fast-evolving Heteropsylla cubana (Psyllidae: Ciriacreminae) was incorrectly placed within the subfamily Psyllinae. This bias can be avoided by using data removal or RY-coding strategies. Together, our results strongly support the family relationship of Aphalaridae + (Carsidaridae + Others), and show that the amino-acid-based concatenation analysis is more robust than nucleotide-based one. Future phylogenomic analysis of psyllid nucleotide sequences should take into account methods such as the RY-coding scheme to address potential systematic biases arising from composition and rate heterogeneities.

Infection patterns of ‘Candidatus Liberibacter europaeus’ in Cacopsylla oluanpiensis, a psyllid pest of Pittosporum pentandrum

‘Candidatus Liberibacter’ is a genus of plant-associated bacteria that can be transmitted by insects of the superfamily Psylloidea. Since many members of this genus are putative causal agents of plant diseases, it is crucial in studying their interactions with the psyllid vectors. However, previous studies have mainly focused on few species associated with diseases of economic significance, and this may potentially hinder the development of a more comprehensive understanding of the ecology of ‘Ca. Liberibacter’. The present study showed that an endemic psyllid species in Taiwan, Cacopsylla oluanpiensis, is infected with a species of ‘Ca. Liberibacter’. The bacterium was present in geographically distant populations of the psyllid and was identified as ‘Ca. Liberibacter europaeus’ (CLeu), a species which generally does not induce plant symptoms. Analysis of CLeu infection densities in male and female C. oluanpiensis with different abdominal colors using quantitative polymerase chain reaction revealed that CLeu infection was not significantly associated with psyllid gender and body color. Instead, CLeu infection had a negative effect on the body sizes of both male and female psyllids, which is influenced by bacterial titer. Investigation on CLeu’s distribution patterns in C. oluanpiensis’s host plant Pittosporum pentandrum indicated that CLeu does not behave as a plant pathogen. Also, results showed that nymph-infested twigs had a greater chance of carrying high loads of CLeu, suggesting that ovipositing females and the nymphs are the main source of the bacterium in the plants. This study is not only the first to formally report the presence of CLeu in C. oluanpiensis and plants in the family Pittosporaceae, but also represents the first record of the bacterium in Taiwan. Overall, the findings in this work broaden the understanding of associations between psyllids and ‘Ca. Liberibacter’ in the field.

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.

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.

Uncovering Symbionts Across the Psyllid Tree of Life and the Discovery of a New Liberibacter Species, "Candidatus" Liberibacter capsica.

Sap-feeding insects in the order Hemiptera associate with obligate endosymbionts that are required for survival and facultative endosymbionts that can potentially modify resistance to stress, enemies, development, and reproduction. In the superfamily Psylloidea, the jumping plant lice (psyllids), less is known about the diversity and prevalence of their endosymbionts compared to other sap-feeding pests such as aphids (Aphididae). To address this knowledge gap, using 16S rRNA sequencing we identify symbionts across divergent psyllid host lineages from around the world. Taking advantage of a new comprehensive phylogenomic analyses of Psylloidea, we included psyllid samples from 44 species of 35 genera of five families, collected from 11 international locations for this study. Across psyllid lineages, a total of 91 OTUs were recovered, predominantly of the Enterobacteriaceae (68%). The diversity of endosymbionts harbored by each psyllid species was low with an average of approximately 3 OTUs. Two clades of endosymbionts (clade 1 and 2), belonging to Enterobacteriaceae, were identified that appear to be long term endosymbionts of the psyllid families Triozidae and Psyllidae, respectively. We also conducted high throughput metagenomic sequencing on three Ca. Liberibacter infected psyllid species (Russelliana capsici, Trichochermes walkeri, and Macrohomotoma gladiata), initially identified from 16S rRNA sequencing, to obtain more genomic information on these putative Liberibacter plant pathogens. The phylogenomic analyses from these data identified a new Ca. Liberibacter species, Candidatus Liberibacter capsica, that is a potential pathogen of solanaceous crops. This new species shares a distant ancestor with Ca. L. americanus, which occurs in the same range as R. capsici in South America. We also detected the first association between a psyllid specializing on woody hosts and the Liberibacter species Ca. L. psyllaurous, which is a globally distributed pathogen of herbaceous crop hosts in the Solanaceae. Finally, we detected a potential association between a psyllid pest of figs (M. gladiata) and a Ca. Liberibacter related to Ca. L. asiaticus, which causes severe disease in citrus. Our findings reveal a wider diversity of associations between facultative symbionts and psyllids than previously reported and suggest numerous avenues for future work to clarify novel associations of ecological, evolutionary, and pathogenic interest.

An updated classification of the jumping plant-lice (Hemiptera: Psylloidea) integrating molecular and morphological evidence

The classification of the superfamily Psylloidea is revised to incorporate findings from recent molecular studies, and to integrate a reassessment of monophyla primarily based on molecular data with morphological evidence and previous classifications. We incorporate a reinterpretation of relevant morphology in the light of the molecular findings and discuss conflicts with respect to different data sources and sampling strategies. Seven families are recognised of which four (Calophyidae, Carsidaridae, Mastigimatidae and Triozidae) are strongly supported, and three (Aphalaridae, Liviidae and Psyllidae) weakly or moderately supported. Although the revised classification is mostly similar to those recognised by recent authors, there are some notable differences, such as Diaphorina and Katacephala which are transferred from Liviidae to Psyllidae. Five new subfamilies and one new genus are described, and one secondary homonym is replaced by a new species name. A new or revised status is proposed for one family, four subfamilies, four tribes, seven subtribes and five genera. One tribe and eight genera / subgenera are synonymised, and 32 new and six revised species combinations are proposed. All recognised genera of Psylloidea (extant and fossil) are assigned to family level taxa, except for one which is considered a nomen dubium.

Checklist of jumping plant-lice (Hemiptera, Sternorrhyncha, Psyllidae) from Mato Grosso, Brazil

Os psilídeos são insetos pequenos que se alimentam do floema e se caracterizam por apresentarem uma pequena faixa de plantas hospedeiras em que se desenvolvem. Este trabalho teve como objetivo prospectar e identificar insetos da superfamília de Psylloidea que ocorrem associados a diferentes biomas no Mato Grosso e que resultou na coleta de 29 gêneros descritos, com 24 espécies identificadas. O Cerrado foi o bioma que apresentou a maior diversidade, seguido pela Amazônia e Pantanal. Comparando com a última lista de psilídeos publicada para o Brasil, em 2012, este artigo contribuiu significativamente para o aumento do conhecimento da biodiversidade de Mato Grosso. Além das espécies registradas para o Mato Grosso (Diaphorina citri, Heteropsylla caldwelli, Pseudophacopteron longicaudatum, Tainarys myracrodruie Trioza struthanthi), também apresentamos novos registros para outros estados brasileiros: Isogonoceraia divergipennis– no Maranhão, Rio Grande do Sul, Rio de Janeiro e Santa Catarina; Heteropsylla caldwelli – em Goiás e São Paulo; Euphalerus clitoriae – no Ceará, Goiás, Pará, Paraná e Santa Catarina; Trioza tabebuiae – em Minas Gerais, São Paulo e Santa Catarina; e Trioza struthanthi em São Paulo.

Illuminating Insights into the Biodiversity of the Australian Psyllids (Hemiptera: Psylloidea) Collected Using Light Trapping.

The superfamily Psylloidea includes numerous species which play a key role in Australian ecology and biodiversity, as well as pests and biological control agents, and sometimes threatened species of conservation concern. Different psyllid sampling and collection techniques are usually performed depending on the nature and aim of the study: from the beating and sweeping of psyllid host plants for conservation and biodiversity assessment, to suction and sticky traps in agriculture. Due to a general lack of information on its efficacy for psyllids, however, light trapping has not usually been employed. Here we present the results obtained trapping psyllids using different light sources and we discuss the strengths and weaknesses of this technique to assess psyllid biodiversity. In particular, we highlight the strength of using this methodology paired with DNA barcoding, to cast some light on psyllid biodiversity. The results obtained here suggest that the psyllid fauna of Australia is heavily understudied and the number of undescribed species might be many times higher than previously expected. Additionally, we report, for the first time, the species Trioza adventicia Tuthill 1952, and Cryptoneossa triangula Taylor 1990 in the state of Queensland.

Higher‐level molecular phylogeny of jumping plant lice (Hemiptera: Sternorrhyncha: Psylloidea)

AbstractJumping plant lice (Hemiptera: Psylloidea) are known for a few deleterious pest species worldwide, yet the phylogeny of the group has been poorly understood until very recently. Here, we reconstruct the higher‐level phylogeny for the superfamily Psylloidea based on multilocus DNA sequences, three mitochondrial (COI‐tRNAleu‐COII, 12S, 16S) and five nuclear (18S, 28S D2, 28S D3, 28S D6–7a, 28S D9–10) gene fragments, using maximum likelihood and Bayesian inference phylogenetic frameworks. Our results are largely congruent with the recent phylogenomic study and partly support prior classification of Psylloidea based mainly on morphology, with the following major exceptions: the family Calophyidae is revealed as polyphyletic, Aphalaridae as paraphyletic with respect to most other taxa of Psylloidea, and Liviidae as paraphyletic with respect to Calophyinae, Psyllidae and Triozidae. Our phylogenetic hypothesis identifies Phacopteronidae and the genus Cecidopsylla Kieffer as the very basal taxa within extant Psylloidea. Sister‐group relationships of Rhinocolinae with Togepsyllinae and of Pachypsyllinae with Homotomidae are also suggested. We present specific discussions for each group of interest recovered in our phylogenetic analysis. One nomenclatorial change is proposed: Spanioneura longicauda (Konovalova) comb.n., from Psylla Geoffroy.

Detection of telomeric sequences and ribosomal RNA genes in holokinetic chromosomes of five jumping plant-lice species: First data on the superfamily Psylloidea (Hemiptera: Sternorrhyncha)

Fluorescence in situ hybridization (FISH) is a technique used to determine the chromosomal position of DNA and RNA probes. The present study contributes to knowledge on jumping plant-lice genomes by using FISH with 18S rDNA and telomeric (TTAGG)n probes on meiotic chromosomes of Psylla alni (2n = 24 + X), Cacopsylla mali (2n = 22 + neo-XY and 20 + neo-X1X2Y), C. sorbi (2n = 20 + neo-XY), Baeopelma foersteri (2n = 14 + X), and Rhinocola aceris (2n = 10 + X). This is the first study that has used FISH on the hemipteran superfamily Psylloidea. We found that the chromosomes of all studied species contain the insect-type telomere motif, (TTAGG)n. In C. mali and C. sorbi, the neo-sex chromosomes originating from autosome-sex chromosome fusions showed no interstitially located clusters of TTAGG repeats, suggesting their loss or inactivation. Similarly, no interstitial (TTAGG)n clusters were detected in an extremely large autosome pair of B. foersteri that most likely originated from a fusion of at least five ancestral chromosome pairs. Clusters of 18S rDNA were detected on the fused and second largest autosome pairs of B. foersteri and on one of the large autosome pairs of the remaining species. In C. mali and B. foersteri, the rDNA clusters were shown to coincide with the NORs as detected by the AgNOR method. Finally, we speculate, based on the obtained FISH markers, on the mechanisms of karyotype evolution of psylloid species differing in chromosome numbers and sex chromosome systems.

DNA Barcoding Highlights Cryptic Diversity in the New Zealand Psylloidea (Hemiptera: Sternorrhyncha)

The insect superfamily Psylloidea (Hemiptera) includes economically important biocontrol agents, pests and plant pathogen vectors, for which a rapid and accurate identification is fundamental for international biosecurity. Australasia is a hot spot for psyllid diversity, but previous species assessments in the region were largely based on morphology and host plant association. Morphological identification of psyllids remains challenging for a wide number of species and for juvenile insects, while a robust molecular framework for identification is not available. Consequently, knowledge of psyllid biology is compromised. Here, incorporating morphological evidence and host plant associations, insects collected from almost 600 primarily New Zealand locations were linked to 67 previously described species. By applying species delimitation methods including GYMC (General Mixed Yule–Coalescent method), PTP (Poisson Tree Processes), mPTP (multi–rate Poisson Tree Processes) and ABGD (Automatic Barcode Gap Discovery) to a dataset composed of 425 cytochrome oxidase I (COI) DNA barcode sequences, further cryptic diversity was revealed among the psyllid collection; more than 20 undescribed taxa are reported here for the first time, resulting in a total of 90 taxa across 21 genera and six families included in this study. Our improved understanding of psyllid diversity in New Zealand revealed new plant host-psyllid associations and geographical variation. The DNA barcode resource will enable future studies of psyllid ecology and more accurate, rapid identifications of psyllids that pose biosecurity threats to Australasia.

Resolving the psyllid tree of life: phylogenomic analyses of the superfamily Psylloidea (Hemiptera)

AbstractUnderstanding evolutionary relationships in the superfamily Psylloidea is challenging due to the lack of clear morphological synapomorphies for many groups. Some families and many of the genera, including the two largest, Cacopsylla Ossiannilsson and Trioza Foerster, have long been acknowledged as nonmonophyletic and the circumscription of natural groups has remained fluid. We present the best phylogenetic hypothesis to date for Psylloidea and provide a working systematic framework to better reflect evolutionary relationships. A shotgun sequencing approach using mixed pool DNAs for more than 400 species resulted in recovery from de novo assemblies of near‐complete mitogenomes (≥10 kb) for 359 species, and partial genomes (5–10 kb) for an additional 40 species. The resulting phylogeny improves and clarifies the family classification and resolves some of the longstanding uncertainties in relationships within and between genera. A whole‐nuclear‐genome scan approach (yielding data from an estimated 373 nuclear genes) using the anchored hybrid enrichment method for a representative subset of taxa confirms the placement of major groupings and overall tree topology recovered with the mitochondrial data. The data generated represent a major increase in molecular resources for this superfamily. In addition, we highlight areas of remaining uncertainty that require further sampling and/or additional sources of data. The phylogeny provides new insights for both evolutionary and applied research, and a backbone constraint tree allows the placement of taxa of particular interest or concern (e.g. pest taxa) with only small fragments of sequence available (e.g. DNA barcodes).

Elongation Factor-1α Accurately Reconstructs Relationships Amongst Psyllid Families (Hemiptera: Psylloidea), with Possible Diagnostic Implications.

The superfamily Psylloidea (Hemiptera: Sternorrhyncha) lacks a robust multigene phylogeny. This impedes our understanding of the evolution of this group of insects and, consequently, an accurate identification of individuals, of their plant host associations, and their roles as vectors of economically important plant pathogens. The conserved nuclear gene elongation factor-1 alpha (EF-1α) has been valuable as a higher-level phylogenetic marker in insects and it has also been widely used to investigate the evolution of intron/exon structure. To explore evolutionary relationships among Psylloidea, polymerase chain reaction amplification and nucleotide sequencing of a 250-bp EF-1α gene fragment was applied to psyllids belonging to five different families. Introns were detected in three individuals belonging to two families. The nine genera belonging to the family Aphalaridae all lacked introns, highlighting the possibility of using intron presence/absence as a diagnostic tool at a family level. When paired with cytochrome oxidase I gene sequences, the 250 bp EF-1α sequence appeared to be a very promising higher-level phylogenetic marker for psyllids.

First Evidence of Vibrational Communication in Homotomidae (Psylloidea) and Comparison of Substrate-Borne Signals of Two Allied Species of the Genus Macrohomotoma Kuwayama

Substrate-borne signals are widely used in Hemiptera and are known to be utilized in mate searching and recognition. Within this Order, the superfamily Psylloidea is a diverse taxon which uses this type of signal modality during mating behavior between the two sexes. This study describes and compares the previously unreported vibrational communication of two closely related species of Macrohomotoma (Homotomidae). Both genders of these two species, Macrohomotoma gladiata Kuwayama 1908 and Macrohomotoma robusta Yang 1984, emit vibrational signals and establish duets during mating. The structure of male calling consists of two chirps while the female response is a single chirp. Males may sometimes follow the female response by emitting a single chirp that sounds similar to the female response with respect to the chirp duration and dominant frequency. This behavior is novel among Psylloidea and its potential function is discussed. Specific comparison of signal characteristics has revealed that the two species of Macrohomotoma are clearly distinguishable from each other which opens the possibility of acoustic signals being used for species delineation.

Phylogeographic analyses of bacterial endosymbionts in fig homotomids (Hemiptera: Psylloidea) reveal codiversification of both primary and secondary endosymbionts.

While obligate primary (P-) endosymbionts usually cospeciate with their insect hosts, less is known about codiversification of secondary (S-) endosymbionts that are generally considered facultative. Typically, insects of the superfamily Psylloidea harbour one P- (Carsonella) and at least one S-endosymbiont, thought to compensate for Carsonella genome reduction. Most codiversification studies have used phylogenies of psyllids and their endosymbionts across and within host families or genera, but few have explored patterns within species. We focussed on P- and S-endosymbionts of three Mycopsylla (Homotomidae) species to explore whether they have congruent phylogenies and within-species geographic structures. The P-endosymbiont Carsonella, a S-endosymbiont and Wolbachia all had 100% prevalence, while Arsenophonus was only found in one species at low prevalence. Congruent phylogenies of Mycopsylla and P-endosymbionts across populations and species support strict cospeciation.S-endosymbiont phylogenies were also congruent across host species but low genetic variation in the S-endosymbiont was not correlated with host phylogeography, possibly due to a shorter evolutionary association. Between species, Wolbachia and Mycopsylla phylogenies were incongruent, probably due to horizontal transmission events. Our study is the first to explore endosymbionts of Mycopsylla and further supports the codivergence of Psylloidea hosts and P-endosymbionts, with obligate host interactions for both P- and S-endosymbionts.

Deep Characterization of the Microbiomes of Calophya spp. (Hemiptera: Calophyidae) Gall-Inducing Psyllids Reveals the Absence of Plant Pathogenic Bacteria and Three Dominant Endosymbionts.

Bacteria associated with sap-feeding insect herbivores include not only symbionts that may increase their hosts’ fitness but also harmful plant pathogens. Calophya spp. gall-inducing psyllids (Hemiptera: Calophyidae) are being investigated for their potential as biological control agents of the noxious weed, Brazilian peppertree (Schinus terebinthifolia), in Florida. Although there are no examples of plant pathogen transmission by members of the family Calophyidae, several insects in the superfamily Psylloidea are known to transmit pathogenic bacteria in the genera Candidatus Liberibacter and Candidatus Phytoplasma. To determine whether Calophya spp. harbor potentially harmful plant pathogenic bacteria, we sequenced small subunit (SSU) ribosomal RNA (rRNA) gene amplicons generated from individuals from four Calophya spp. populations. All microbial SSU gene sequences fell into the bacterial domain, with 98-99% belonging to the Proteobacteria. The Calophya microbiomes contained a relatively simple community, with 49-79 operational taxonomic units (OTUs; 97%) detected, and only 5-8 OTUs with greater than 1% abundance. Candidatus Carsonella showed the highest relative abundance, with OTUs from this candidate genus representing between 51 – 65% of all recovered sequences. The next most abundant clade observed was an unclassified Enterobacteriacae group closely related to bacteria from the genera Buchnera and Blochmannia that ranged from 20-31% in relative abundance. Wolbachia populations were the third most abundant group and represented 7-27% of the diversity in microbial OTUs. No SSU rRNA gene sequences from putative pathogenic bacteria from the genera Ca. Liberibacter or Ca. Phytoplasma were detected in the microbiomes of the four Calophya populations. The probability that infected psyllids were present in our colonies, but were not sampled, was extremley low (1.39 x 10-10). As far as we are aware, our study is the first to characterize the microbiome of a candidate biological control agent, and coupled with previous work demonstrating a high degree of host specificity and absence of plant viruses, suggests that releasing Calophya spp. in United States poses minimal risk to non-target plants.

Search for potential vectors of ‘Candidatus Liberibacter solanacearum’: population dynamics in host crops

‘Candidatus Liberibacter solanacearum’ has recently been reported to be associated with vegetative disorders and economic losses in carrot and celery crops in Spain. The bacterium is a carrot seedborne pathogen and it is transmitted by psyllid vector species. From 2011 to 2014 seasonal and occasional surveys in carrot, celery and potato plots were performed. The sticky plant method was used to monitor the arthropods that visited the plants. The collected arthropods were classified into Aphididae and Cicadellidae, and the superfamily Psylloidea was identified to the species level. The superfamily Psylloidea represented 35.45% of the total arthropods captured on celery in Villena and 99.1% on carrot in Tenerife (Canary Islands). The maximum flight of psyllid species was in summer, both in mainland Spain and the Canary Islands, reaching a peak of 570 specimens in August in Villena and 6,063 in July in Tenerife. The main identified psyllid species were as follows: Bactericera trigonica Hodkinson, B. tremblayi Wagner and B. nigricornis Förster. B. trigonica represented more than 99% of the psyllids captured in the Canary Islands and 75% and 38% in 2011 and 2012 in Villena, respectively. In addition, Trioza urticae Linnaeus, Bactericera sp., Ctenarytaina sp., Cacopsylla sp., Trioza sp. and Psylla sp. were captured. ‘Ca. L. solanacearum’ targets were detected by squash real-time PCR in 19.5% of the psyllids belonging to the different Bactericera species. This paper reports at least three new psyllid species that carry the bacterium and can be considered as potential vectors.

Spread of European fruit tree phytoplasma diseases

The genetically closely related ‘Candidatus Phytoplasma mali’, ‘Candidatus Phytoplasma prunorum’ and ‘Candidatus Phytoplasma pyri’ are associated with economically important diseases such as apple proliferation, European stone fruit yellows and pear decline in European fruit tree areas and are spread by psyllid vectors of the superfamily Psylloidea (Hemiptera, Sternorrhyncha). Although the relationship between these phytoplasmas, their hosts and the vectoring psyllids is almost highly specific, there are some interconnections and biological factors which influence disease epidemiology and vector ecology and which should be taken into consideration for risk assessment and vector control. For a reliable risk assessment of a putative vector is important to know its population dynamics, its transmission efficiency, its host plant preferences and its epidemiological cycle. Although psyllid vectors usually show a high host plant specificity, being either monophagous or oligophagous on closely related plant species, shelter plants may serve as sources of inoculum and hence interfere with the disease spread. Therefore, the knowledge of the epidemiological cycle of both, the phytoplasma and its main vector is crucial for the development of efficient control measures.