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Abstract: Many herbivorous insect species exhibit phenotypic plasticity when using multiple hosts, which facilitates survival in heterogeneous host environments. Physiological host acclimation is an important part of it, yet the effects of host acclimation on insect feeding behaviour are not well studied, particularly for insect vectors of plant pathogens. We studied the combined effects of host acclimation and infection with a plant pathogenic symbiont on feeding behaviour of Bactericera cockerelli, an oligophagous psyllid widespread in both crop and natural habitats that feed primarily on Solanaceae and transmit an economically important plant pathogen, Candidatus Liberibacter solanacearum (CLso). We used a factorial design and the electrical penetration graphing technique to disentangle the effects of host acclimation, CLso infection and psyllid haplotype on the within‐plant feeding behaviour of B. cockerelli during conspecific and heterospecific host switches. This approach allows to connect phenotypic plasticity with the role of B. cockerelli as a vector by quantifying the frequency and duration of behaviours involved in CLso transmission. We found significant reductions in multiple metrics of B. cockerelli feeding efficiency, exacerbated by infection with CLso, which could lead to reduced transmission of this pathogen. Psyllid genotype was also important; the Central haplotype exhibited less dramatic changes in feeding efficiency than the Western haplotype during heterospecific host switches. Our study shows that host acclimation and heterospecific host switching directly alter feeding behaviours underlying pathogen transmission, and that the magnitude of feeding efficiency reductions depends on both host genotype and infection status.

The tomato-potato psyllid (TPP) Bactericera cockerelli is an important pest of several solanaceous crops. The current pest management strategy based on synthetic insecticides is being challenged through the development of pesticide resistance and environmental concerns. This contribution investigates the biological control potential of the mirid bug Engytatus nicotianae, either alone, or in combination with the parasitic wasp T. triozae, for combating the TPP on infested greenhouse tomato plants. In doing so we measured (a) the efficacy of E. nicotianae in reducing TPP numbers on lightly infested plants and (b) the potential for E. nicotianae and T. triozae in combination for effective biological control. In the E. nicotianae only treatment, the predator reduced the number of TPP-infested leaves, but the TPP population reduction was not significant. Conversely, the combined E. nicotianae + T. triozae treatment did show a consistent and significant reduction of TPP-infested leaves as well as TPP populations. These findings suggest that using a combination of the two species might deliver a biological control of TPP under glasshouse conditions. Further research is needed to determine the optimum ratio of E. nicotianae and T. triozae release-densities under different levels of TPP infestation and how this may translate from caged conditions to greenhouse performance. HIGHLIGHTS: Engytatus nicotianae alone was not enough for the control of an established TPP population on tomatoes Combined releases of E. nicotianae and Tamarixia triozae markedly reduced the TPP population on caged tomatoes The study's outcome can address some gaps in the biological control of TPP on greenhouse tomatoes. [ABSTRACT FROM AUTHOR]

Lineage-specific gene expansions may allow insects to adapt and diverge functional traits. The Hansen lab’s chromosomal assembly of the sap-sucking potato psyllid (Bactericera cockerelli) previously identified three rapidly evolving genes associated with protease expression. The current study further analyzed whether or not plant diet and insect life stage might impact protease expression. We fed insects differ- ent plant diets of either potato or tomato at two insect life stages (2nd instar and young adult) to test for differences in insect protease gene expression. First, RNA extractions were conducted, followed by quantitative PCR (qPCR). The study used the Δ-Δ Ct method to analyze the relative comparison of gene expression between two genes and the ANOVA test to determine if there is a relationship between the changes in gene expression. Preliminary data revealed a significant difference between the host plant diets potato and tomato for 2nd instar nymphs for two of the three candidate genes. This project begins laying the foundation for iden- tifying the function of species-specific protease genes that are evolving rapidly in the insect, and ultimately these genes may be involved in host plant adaptation.

The tomato-potato psyllid, Bactericera cockerelli (Šulc), belonging to the Hemiptera order, is an insect pest of solanaceous crops and vectors a fastidious bacterium, Candidatus Liberibacter solanacearum (CLso), the presumptive causal agent of zebra chip and vein greening diseases in potatoes and tomatoes, respectively. The genome of B. cockerelli has been sequenced recently, providing new avenues to elucidate mechanistic insights into pathogenesis in vegetable crops. In this study, we performed RNA-sequencing of the critical psyllid organs (salivary glands and ovaries) involved in CLso pathology and transmission to host plants. Transcriptome analysis revealed differentially expressed genes and organ-specific enrichment of gene ontology (GO) terms related to metabolic processes, response to stress/stimulus, phagocytosis, proteolysis, endocytosis, and provided candidate genes encoding transcription factors (TFs). To examine gene regulatory networks across the psyllid organs under CLso(-) and CLso(+) conditions, we performed weighted gene co-expression network analysis (WGCNA), and unique modules differentiating the psyllid organs were identified. A comparative GO analysis of the unique gene modules revealed functional terms enriched in response to stress, gene regulation, and cell division processes in the ovaries. In contrast, respiration, transport, and neuronal transmission-related GO terms were enriched in the salivary glands. Altogether, this study reveals new insights into tissue-specific expression of the psyllid organs in the absence or presence of CLso bacterium. This knowledge can be leveraged to develop new pest and disease management strategies by delineating the regulatory networks involved in the psyllid-CLso interaction. [ABSTRACT FROM AUTHOR]

The tomato potato psyllid, Bactericera cockerelli Šulc, originating from North and Central America, poses a serious threat to Solanaceae crops in Australia. This study investigates the potential of the Australian native and commercially available green lacewing, Mallada signatus Schneider, as a biological control agent for B. cockerelli. The effect of feeding on B. cockerelli on the development rate and survival, of M. signatus were evaluated. Further, a greenhouse cage study was conducted to determine the optimal density of M. signatus larvae needed to effectively control an established B. cockerelli population. In our study, the third instar larvae of M. signatus consumed over 75 B. cockerelli nymphs in 24 h. Following the introduction of M. signatus larvae to caged tomato plants, eight M. signatus larvae per caged tomato plant decreased B. cockerelli population by 64% at the end of the sampling. These results indicated M. signatus, particularly at the larval stage, is an effective biological control option for B. cockerelli, especially in greenhouse tomato cultivation. This research offers valuable insights for the Australian horticultural industry, presenting a viable, eco‐friendly alternative to traditional, chemical pesticide‐reliant pest management strategies. [ABSTRACT FROM AUTHOR]

Lineage specific expansions and gene duplications are some of the most important sources of evolutionary novelty in eukaryotes. Although not as prevalent in eukaryotes compared to bacteria, horizontal gene transfer events can also result in key adaptations for insects, especially for those involved in insect-microbe interactions. In this study we assemble the first chromosomal assembly of the psyllid Bactericera cockerelli and reveal that the B. cockerelli genome has experienced significantly more gene expansion events compared to other Hemipteran representatives with fully sequenced genomes. We also reveal that B. cockerellis genome is the largest psyllid genome (567 Mb) sequenced to date and is ~15% larger than the other two psyllid species genomes sequenced (Pachypsylla venusta and Diaphorina citri). Structurally, B. cockerelli appears to have an additional chromosome compared to the distantly related psyllid species P. venusta due to a previous chromosomal fission or fusion event. The increase in genome size and dynamic nature of the B. cockerelli genome may largely be contributed to the widespread expansion of type I and II repeat elements that are rampant across all of B. cockerellis. chromosomes. These repeat elements are distributed near equally in both euchromatic and heterochromatic regions. Furthermore, significant gene family expansions and gene duplications were uncovered for genes that are expected to be important in its adaptation to insect-plant and microbe interactions, which include transcription factors, proteases, odorant receptors, and horizontally transferred genes that are involved in the nutritional symbioses with their long-term nutritional endosymbiont Carsonella.

The tomato-potato psyllid, Bactericera cockerelli (Šulc), belonging to the Hemiptera order, is an insect pest of solanaceous crops and vectors a fastidious bacterium, Candidatus Liberibacter solanacearum (CLso), the presumptive causal agent of zebra chip and vein greening diseases in potatoes and tomatoes, respectively. The genome of B. cockerelli has been sequenced recently, providing new avenues to elucidate mechanistic insights into pathogenesis in vegetable crops. In this study, we performed RNA-sequencing of the critical psyllid organs (salivary glands and ovaries) involved in CLso pathology and transmission to host plants. Transcriptome analysis revealed differentially expressed genes and organ-specific enrichment of gene ontology (GO) terms related to metabolic processes, response to stress/stimulus, phagocytosis, proteolysis, endocytosis, and provided candidate genes encoding transcription factors (TFs). To examine gene regulatory networks across the psyllid organs under CLso(-) and CLso(+) conditions, we performed weighted gene co-expression network analysis (WGCNA), and unique modules differentiating the psyllid organs were identified. A comparative GO analysis of the unique gene modules revealed functional terms enriched in response to stress, gene regulation, and cell division processes in the ovaries. In contrast, respiration, transport, and neuronal transmission-related GO terms were enriched in the salivary glands. Altogether, this study reveals new insights into tissue-specific expression of the psyllid organs in the absence or presence of CLso bacterium. This knowledge can be leveraged to develop new pest and disease management strategies by delineating the regulatory networks involved in the psyllid-CLso interaction.

Introduction: The potato psyllid Bactericera cockerelli is the insect vector of the fastidious bacterium 'Candidatus Liberibacter solanacearum'. The bacterium infects both B. cockerelli and plant species, causing zebra chip (ZC) disease of potato and vein-greening disease of tomato. Temperatures are known to influence the initiation and progression of disease symptom in the host plant, and seasonal transitions from moderate to high temperatures trigger psyllid dispersal migration to facilitate survival. Methods: 'Ca. L. solanacearum' -infected and uninfected psyllids were reared at previously established 'permissible', optimal, and'non-permissible' and temperatures of 18°C, 24°C, and 30°C, respectively. Gene expression profiles for 'Ca. L. solanacearum'-infected and -uninfected adult psyllids reared at different temperatures were characterized by Illumina RNA-Seq analysis. Bacterial genome copy number was quantified by real-time quantitative-PCR (qPCR) amplification. Results: Relative gene expression profiles varied in psyllids reared at the three experimental temperatures. Psyllids reared at 18°C and 30°C exhibited greater fold-change increased expression of stress- and 'Ca. L. solanacearum' invasionrelated proteins. Quantification by qPCR of bacterial genome copy number revealed that 'Ca. L. solanacearum' accumulation was significantly lower in psyllids reared at 18°C and 30°C, compared to 24°C. Discussion: Temperature is a key factor in the life history of potato psyllid and multiplication/accumulation of 'Ca. L. solanacearum' in both the plant and psyllid host, influences the expression of genes associated with thermal stress tolerance, among others, and may have been instrumental in driving the coevolution of the pathosystem. [ABSTRACT FROM AUTHOR]

Historically it has been difficult to study the evolution of bacterial small RNAs (sRNAs) across distantly related species. For example, identifying homologs of sRNAs is often difficult in genomes that have undergone multiple structural rearrangements. Also, some types of regulatory sRNAs evolve at rapid rates. The high degree of genomic synteny among divergent host-restricted bacterial lineages, including intracellular symbionts, is conducive to sRNA maintenance and homolog identification. In turn, symbiont genomes can provide us with novel insights into sRNA evolution. Here, we examine the sRNA expression profile of the obligate symbiont of psyllids, Carsonella ruddii, which has one of the smallest cellular genomes described. Using RNA-seq, we identified 36 and 32 antisense sRNAs (asRNAs) expressed by Carsonella from the psyllids Bactericera cockerelli (Carsonella-BC) and Diaphorina citri (Carsonella-DC), respectively. The majority of these asRNAs were associated with genes that are involved in essential amino acid biosynthetic pathways. Eleven of the asRNAs were conserved in both Carsonella lineages and the majority were maintained by selection. Notably, five of the corresponding coding sequences are also the targets of conserved asRNAs in a distantly related insect symbiont, Buchnera. We detected differential expression of two asRNAs for genes involved in arginine and leucine biosynthesis occurring between two distinct Carsonella-BC life stages. Using asRNAs identified in Carsonella, Buchnera, and Profftella which are all endosymbionts, and Escherichia coli, we determined that regions upstream of these asRNAs encode unique conserved patterns of AT/GC richness, GC skew, and sequence motifs which may be involved in asRNA regulation.

RT-PCR was used to test whether DNA from potato psyllid (Bactericera cockerelli (Šulc)) could be detected in generalist predators that had been allowed to feed on psyllids in laboratory feeding trials. The assay used primers that had been developed in Europe to amplify a region of the ITS2 gene in psyllids for use in identifying psyllid specimens intercepted at border inspection stations or discovered in regions currently free of the pest. We conducted feeding trials with arthropod generalist predators in diverse taxonomic groups (Araneae, Acari, and two orders of Insecta). RT-PCR readily detected potato psyllid DNA in predators that had recently fed upon the insect. DNA from a closely related psyllid, Bactericera dorsalis (Crawford), was not detected, suggesting that our approach is unlikely to lead to false positives. RT-PCR was found to be more sensitive than conventional PCR at detecting very dilute quantities of potato psyllid DNA. Predator taxa differed in how long after a feeding event prey DNA could be detected. Signal retention was longer in spiders and a predatory mite (Anystis) than in predatory true bugs (Hemiptera). We believe this new molecular tool will be of value in identifying potentially important sources of psyllid biological control under field conditions. [ABSTRACT FROM AUTHOR]

'Candidatus Liberibacter solanacearum' (Lso) is a bacterial pathogen that causes 'zebra chip' disease in potato. Vectored by the potato psyllid Bactericera cockerelli, Lso inflicts severe economic losses annually in solanaceous and other crops. Conventional management strategies have been insufficient to control the pathogen. As an environmentally friendly phytosanitary technique, electron beam (eBeam) irradiation has been shown to drastically suppress psyllid growth and development. However, whether this chemical-free technology negatively impacts the pathogen transmission remains to be investigated. In this study, we irradiated newly emerged adult psyllids and measured abundance of Lso they carried. An eBeam dose of 100 Gy significantly suppressed Lso in irradiated psyllids, although a rebound was detected on day 7 post irradiation. This resumed bacterial growth was not observed in psyllids irradiated at 250 or 500 Gy. Electrical penetration graphs revealed that eBeam substantially impacted psyllid feeding activity. No significant difference was detected in actin cytoskeleton structure and nucleus integrity of its midgut cells 1 or 7 days post eBeam irradiation at 500 Gy. Furthermore, infection of tomato plants was drastically reduced when fed upon by psyllids exposed to 250 Gy and undetectable at 500 Gy. Thus, eBeam significantly lowered psyllid's transmission efficiency and even abolished this capacity. Taken together, eBeam irradiation curtailed Lso titers in potato psyllids and impaired its bacterial transmission. Our results have demonstrated the real potential of irradiation technology in management of insect-vectored diseases. [ABSTRACT FROM AUTHOR]

Potato (Solanum tuberosum L.) occupies the first place among roots and tubers planted in Cuba, with yields that have decreased in the last decade. One of the great limitations in potato production are diseases, which affect plants and tubers. The aphids Myzus persicae Sulc and Aphis gossypii Glover are the main species that directly affect the crop in addition to acting as vectors of viral diseases casing the greatest losses to the crop. On the other hand, the manifestations of climate change and trade favor the introduction of new pests such as Bactericera cockerelii Sulc, a potential pest of great importance for the crop. Based on these elements, the objective of this study was to carry out a bibliographic review that made it possible to make available elements that increased knowledge about the identification of vectors and the diseases of probable occurrence in potato to researchers, decision-makers, and technicians. This review will provide them with aspects for the identification, distribution, hosts, damage, and biology of these insects, as well as management methods for their surveillance. From various databases, 41 papers published in journals between 1987 and 2023 were selected. . They will contribute to preserving one of the crops that, due to its productive efficiency and consumption, allows guaranteeing food security of the country. [ABSTRACT FROM AUTHOR]

Transmission of insect-borne pathogens is mediated by interactions between insects and plants across variable environments. Water stress, for example, affects the physiology, defense, chemistry, and nutritional balance of plants in ways that alter their tolerance to herbivores and pathogens. However, few studies have explored interactions between water stress and insect-borne pathogens as well as the molecular mechanisms mediating these interactions. Here, we address these knowledge gaps by assessing effects of plant water stress on the transmission of a bacterial pathogen, Candidatus Liberibacter solanacearum (CLs), by the vector Bactericera cockerelli Šulc (potato psyllid). We hypothesized that plant water stress would promote pathogen transmission by inducing plant gene transcripts and phytohormones involved in defense. Our results showed water stress was associated with decreased CLs titer with two psyllid haplotypes. Our analysis of plant gene transcripts suggested water stress affected phytohormone pathways in ways that altered plant tolerance to the CLs pathogen. Our study shows that abiotic stressors like drought may mediate the spread of plant pathogens by altering plant signaling pathways in ways that affect pathogen transmission. [ABSTRACT FROM AUTHOR]

Some facultative bacterial symbionts are known to benefit insects, but nutritional advantages are rare among these non-obligate symbionts. Here, we demonstrate that the facultative symbiont Candidatus Liberibacter psyllaurous enhances the fitness of its psyllid insect host, Bactericera cockerelli , by providing nutritional benefits. L. psyllaurous , an unculturable pathogen of solanaceous crops, also establishes a close relationship with its insect vector, B. cockerelli , increasing in titer during insect development, vertically transmitting through eggs, and colonizing various tissues, including the bacteriome, which houses the obligate nutritional symbiont, Carsonella. Carsonella supplies essential amino acids to its insect host but has gaps in some of its essential amino acid pathways that the psyllid complements with its own genes, many of which have been acquired through horizontal gene transfer (HGT) from bacteria. Our findings reveal that L. psyllaurous increases psyllid fitness on plants by reducing developmental time and increasing adult weight. In addition, through metagenomic sequencing, we reveal that L. psyllaurous maintains complete pathways for synthesizing the essential amino acids arginine, lysine, and threonine, unlike the psyllid's other resident microbiota, Carsonella, and two co-occurring Wolbachia strains. RNA sequencing reveals the downregulation of a HGT collaborative psyllid gene ( ASL ), which indicates a reduced demand for arginine supplied by Carsonella when the psyllid is infected with L. psyllaurous . Notably, artificial diet assays show that L. psyllaurous enhances psyllid fitness on an arginine-deplete diet. These results corroborate the role of L. psyllaurous as a beneficial insect symbiont, contributing to the nutrition of its insect host.IMPORTANCEUnlike obligate symbionts that are permanently associated with their hosts, facultative symbionts rarely show direct nutritional contributions, especially under nutrient-limited conditions. This study demonstrates, for the first time, that Candidatus Liberibacter psyllaurous , a facultative symbiont and a plant pathogen, enhances the fitness of its Bactericera cockerelli host by supplying an essential nutrient arginine that is lacking in the plant sap diet. Our findings reveal how facultative symbionts can play a vital role in helping their insect hosts adapt to nutrient-limited environments. This work provides new insights into the dynamic interactions between insect hosts, their symbiotic microbes, and their shared ecological niches, broadening our understanding of symbiosis and its role in shaping adaptation and survival.

Abstract Background The tomato psyllid, Bactericera cockerelli Šulc (Hemiptera: Triozidae), is a pest of solanaceous crops such as tomato (Solanum lycopersicum L.) in the U.S. and vectors the disease-causing pathogen ‘Candidatus Liberibacter solanacearum’ (or Lso). Disease symptom severity is dependent on Lso haplotype: tomato plants infected with Lso haplotype B experience more severe symptoms and higher mortality compared to plants infected with Lso haplotype A. By characterizing the molecular differences in the tomato plant’s responses to Lso haplotypes, the key components of LsoB virulence can be identified and, thus, targeted for disease mitigation strategies. Results To characterize the tomato plant genes putatively involved in the differential immune responses to Lso haplotypes A and B, RNA was extracted from tomato ‘Moneymaker’ leaves 3 weeks after psyllid infestation. Gene expression levels were compared between uninfected tomato plants (i.e., controls and plants infested with Lso-free psyllids) and infected plants (i.e., plants infested with psyllids infected with either Lso haplotype A or Lso haplotype B). Furthermore, expression levels were compared between plants infected with Lso haplotype A and plants infected with Lso haplotype B. A whole transcriptome analysis identified 578 differentially expressed genes (DEGs) between uninfected and infected plants as well as 451 DEGs between LsoA- and LsoB-infected plants. These DEGs were primarily associated with plant defense against abiotic and biotic stressors, growth/development, plant primary metabolism, transport and signaling, and transcription/translation. These gene expression changes suggested that tomato plants traded off plant growth and homeostasis for improved defense against pathogens, especially when infected with LsoB. Consistent with these results, tomato plant growth experiments determined that LsoB-infected plants were significantly stunted and had impaired negative geotropism. However, it appeared that the defense responses mounted by tomatoes were insufficient for overcoming the disease symptoms and mortality caused by LsoB infection, while these defenses could compensate for LsoA infection. Conclusion The transcriptomic analysis and growth experiments demonstrated that Lso-infected tomato plants underwent gene expression changes related to abiotic and biotic stressors, impaired growth/development, impaired plant primary metabolism, impaired transport and signaling transduction, and impaired transcription/translation. Furthermore, the transcriptomic analysis also showed that LsoB-infected plants, relative to LsoA-infected, experienced more severe stunting, had improved responses to some stressors and impaired responses to others, had poorer transport and signaling transduction, and had impaired carbohydrate synthesis and photosynthesis.

Cost efficiency in biosecurity surveillance is vital, and the ability to survey multiple pest species using just one trap is, therefore, highly appealing. The Psylloidea, or plantlice, contain significant horticultural pest species that act as vectors for a number of deleterious plant bacteria. We examine the efficacy of using two different coloured sticky traps, and two semiochemical lures on the general Psylloidea and Pentatomoidea fauna, and a target extant pest psyllid; tomato potato psyllid (TPP) Bactericera cockerelli (Šulc) in Western Australia. Specifically, we test the effect of semiochemical lure (no lure, Asian citrus psyllid ACP lure, brown marmorated stink bug BMSB lure, combined lures), sticky trap colour (yellow‐green vs yellow) and sentinel plant (tomato vs citrus) on psyllid and pentatomid species in 104 urban backyards across Perth, Australia. We found that tomato sentinel host plants and yellow‐green traps significantly increased the capture rate of TPP, but that lures decreased the capture of TPP constraining their use. Yellow‐green traps also increased the capture rate of all other Psylloidea. Although BMSB lures reduced TPP capture, these lures increased the abundances of other Psylloidea and the pest stinkbug Plautia affinis (Dallas) on traps. Thus, our experiment demonstrates that increased efficiencies can be gained with multi‐species traps and semiochemical lures for particular groups, provided that they have been tested on focal organisms in the first instance, as reactions to non‐target lures are unpredictable and species specific. [ABSTRACT FROM AUTHOR]

Background: The tomato psyllid, Bactericera cockerelli Šulc (Hemiptera: Triozidae), is a pest of solanaceous crops such as tomato (Solanum lycopersicum L.) in the U.S. and vectors the disease-causing pathogen 'Candidatus Liberibacter solanacearum' (or Lso). Disease symptom severity is dependent on Lso haplotype: tomato plants infected with Lso haplotype B experience more severe symptoms and higher mortality compared to plants infected with Lso haplotype A. By characterizing the molecular differences in the tomato plant's responses to Lso haplotypes, the key components of LsoB virulence can be identified and, thus, targeted for disease mitigation strategies. Results: To characterize the tomato plant genes putatively involved in the differential immune responses to Lso haplotypes A and B, RNA was extracted from tomato 'Moneymaker' leaves 3 weeks after psyllid infestation. Gene expression levels were compared between uninfected tomato plants (i.e., controls and plants infested with Lso-free psyllids) and infected plants (i.e., plants infested with psyllids infected with either Lso haplotype A or Lso haplotype B). Furthermore, expression levels were compared between plants infected with Lso haplotype A and plants infected with Lso haplotype B. A whole transcriptome analysis identified 578 differentially expressed genes (DEGs) between uninfected and infected plants as well as 451 DEGs between LsoA- and LsoB-infected plants. These DEGs were primarily associated with plant defense against abiotic and biotic stressors, growth/development, plant primary metabolism, transport and signaling, and transcription/translation. These gene expression changes suggested that tomato plants traded off plant growth and homeostasis for improved defense against pathogens, especially when infected with LsoB. Consistent with these results, tomato plant growth experiments determined that LsoB-infected plants were significantly stunted and had impaired negative geotropism. However, it appeared that the defense responses mounted by tomatoes were insufficient for overcoming the disease symptoms and mortality caused by LsoB infection, while these defenses could compensate for LsoA infection. Conclusion: The transcriptomic analysis and growth experiments demonstrated that Lso-infected tomato plants underwent gene expression changes related to abiotic and biotic stressors, impaired growth/development, impaired plant primary metabolism, impaired transport and signaling transduction, and impaired transcription/translation. Furthermore, the transcriptomic analysis also showed that LsoB-infected plants, relative to LsoA-infected, experienced more severe stunting, had improved responses to some stressors and impaired responses to others, had poorer transport and signaling transduction, and had impaired carbohydrate synthesis and photosynthesis. [ABSTRACT FROM AUTHOR]

Zebra chip disease (ZC), associated with the plant pathogenic bacterium 'Candidatus Liberibacter solanacearum' (psyllaurous) (CLso), is a major threat to global potato production. In addition to yield loss, CLso infection causes discoloration in the tubers, rendering them unmarketable. CLso is transmitted by the potato psyllid, Bactericera cockerelli (Šulc) (Hemiptera: Triozidae). ZC is managed by prophylactic insecticide applications to control the vector, which is costly and carries environmental and human health risks. Given the expense, difficulty, and unsustainability of managing vector‐borne diseases with insecticides, identifying sources of resistance to CLso and developing varieties that are resistant or tolerant to CLso and/or potato psyllids has become a major goal of breeding efforts. These efforts include field and laboratory evaluations of noncultivated germplasm and cultivars, studies of tubers in cold storage, detailed quantifications of biochemical responses to infection with CLso, possible mechanisms underlying insect resistance, and traditional examination of potato quality following infections. This review provides a brief history of ZC and potato psyllid, a summary of currently available tools to manage ZC, and a comprehensive review of breeding efforts for ZC and potato psyllid management within the greater context of Integrated Pest Management (IPM) strategies. © 2022 Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Potato zebra chip (ZC) disease, associated with the uncultured phloem-limited bacterium, Candidatus Liberibacter solanacearum (CLso), is transmitted by the potato psyllid Bactericera cockerelli. Potato ZC disease poses a significant threat to potato production worldwide. Current management practices mainly rely on the control of the psyllid to limit the spread of CLso. The present study investigated new sources of ZC resistance among wild Solanum species. A taxonomically diverse collection of tuber-bearing Solanum species was screened; one ZC-resistant accession and three ZC-tolerant accessions were identified among the 52 screened accessions. Further characterization of the resistant accession showed that the resistance was primarily associated with antibiosis effects due to differences in leaf trichome density and morphology of the wild accession, which could limit the psyllid feeding and oviposition. This germplasm offers a good resource for further understanding ZC and psyllid resistance mechanisms, contributing to potato breeding efforts to develop ZC resistance cultivars. Alternatively, it could be used as a potential trap crop to manage psyllid and control ZC disease. [ABSTRACT FROM AUTHOR]

Potato zebra chip (ZC) disease, associated with the uncultured phloem-limited bacterium, Candidatus Liberibacter solanacearum (CLso), is transmitted by the potato psyllid Bactericera cockerelli. Potato ZC disease poses a significant threat to potato production worldwide. Current management practices mainly rely on the control of the psyllid to limit the spread of CLso. The present study investigated new sources of ZC resistance among wild Solanum species. A taxonomically diverse collection of tuber-bearing Solanum species was screened; one ZC-resistant accession and three ZC-tolerant accessions were identified among the 52 screened accessions. Further characterization of the resistant accession showed that the resistance was primarily associated with antibiosis effects due to differences in leaf trichome density and morphology of the wild accession, which could limit the psyllid feeding and oviposition. This germplasm offers a good resource for further understanding ZC and psyllid resistance mechanisms, contributing to potato breeding efforts to develop ZC resistance cultivars. Alternatively, it could be used as a potential trap crop to manage psyllid and control ZC disease.

Tomato potato psyllid (TPP), Bactericera cockerelli (Sulc) (Hemiptera: Triozidae), is the vector for "Candidatus Liberibacter solanacearum" (CLso), which causes the serious disease "zebra chip" (ZC) of potatoes. Between 2016 and 2019, a reduced-insecticide approach to control TPP was evaluated. We compared a standard-insecticide weekly spray regime that included Integrated Pest Management (IPM)-compatible insecticides plus JMS Stylet Oil® (JMS) as a wetting agent, with a reduced-insecticide regime where we used the oil on its own on alternate weeks with the insecticide/oil mixtures. Spray programme start dates were determined by: (1) crop scouting; (2) sticky-trap monitoring; and (3) degree-day calculation. Crop scouting combined with a sticky-trap action threshold and degree-day data was an effective method for determining when to start spraying. The most substantial reduction in insecticides was achieved by alternating weekly insecticides with the oil formulation on its own. Sub-samples of TPP from sticky traps situated in the trials tested for CLso confirmed the presence of the bacteria in (commonly known as 'hot') TPP throughout the trials. The reduced-treatment approach gave statistically similar levels of ZC to the standard insecticide spray programme. [ABSTRACT FROM AUTHOR]

The psyllid Bactericera cockerelli was first reported in New Zealand in 2006 and spread quickly throughout all potato growing regions. In 2009, B. cockerelli was associated with the plant pathogenic bacterium Candidatus Liberibacter solanacearum, the putative causal agent of zebra chip disease in potato. Both the psyllid and the bacterium have non-crop host plants which can serve as reservoirs when the crop is not available. Growers apply different management strategies that fit integrated pest management programmes to manage B. cockerelli and subsequently lower incidence of zebra chip disease in potato crops. Despite best management efforts, complete control of B. cockerelli and zero incidence of zebra chip disease are not achievable at the current time.

The potato psyllid Bactericera cockerelli (Hemiptera: Triozidae) has recently emerged as a serious pest of potatoes and other solanaceous crops. It causes direct feeding damage and also vectors Candidatus Liberibacter solanaceaerum (Lso), a pathogen that causes zebra chip disease in potatoes and which potentially costs growers millions of dollars each year. Such producers rely on frequent sprays of pesticides for psyllid control but the results are unsatisfactory and there are negative side effects. The psyllid has spread beyond its native range in southwest US and northern Mexico to Canada, El Salvador, Honduras, Guatemala and Nicaragua via medium to long range dispersal flights perhaps aided by wind currents, and through anthropogenic means. It was accidentally introduced into New Zealand in 2006 and most recently Australia, most likely through the importation of infested plant material. This review summarizes information from studies on the biology, impact and management of B. cockerelli, and highlights the imminent risk of this insect and its associated pathogen invading China, the world's largest producer of fresh potatoes. Development of risk maps leading to increased surveillance, could prevent or delay an incursion and facilitate early detection or eradication should this occur. Long-term management with Lso-tolerant potato cultivars and psyllid control using the parasitic wasp Tamarixia triozae and other natural enemies should be pursued, rather than depending on synthetic pesticides.

“Candidatus Liberibacter solanacearum” (Lso) is a phloem-limited Gram-negative bacterium that infects crops worldwide. In North America, two haplotypes of Lso (LsoA and LsoB) are transmitted by the potato psyllid, Bactericera cockerelli (Šulc), in a circulative and persistent manner. Both haplotypes cause damaging plant diseases (e.g., zebra chip in potatoes). The psyllid gut is the first organ Lso encounters and could be a barrier for its transmission. However, little is known about the psyllid gut immune responses triggered upon Lso infection. In this study, we focused on the apoptotic response in the gut of adult potato psyllids at the early stage of Lso infection. We found that there was no evidence of apoptosis induced in the gut of the adult potato psyllids upon infection with either Lso haplotype based on microscopic observations. However, the expression of the inhibitor of apoptosis IAPP5.2 gene (survivin-like) was significantly upregulated during the period that Lso translocated into the gut cells. Interestingly, silencing of IAPP5.2 gene significantly upregulated the expression of two effector caspases and induced apoptosis in the psyllid gut cells. Moreover, RNA interference (RNAi) of IAPP5.2 significantly decreased the Lso titer in the gut of adult psyllids and reduced their transmission efficiency. Taken together, these observations suggest that Lso might repress the apoptotic response in the psyllid guts by inducing the anti-apoptotic gene IAPP5.2 at an early stage of the infection, which may favor Lso acquisition in the gut cells and facilitate its transmission by potato psyllid.

Bactericera cockerelli Sulc, the potato / tomato psyllid (Solanum tuberosum and S. lycopersicum), is recognized as a threat to the production of solanaceous crops because it is an efficient vector of the bacterium Candidatus Liberibacter solanacearum (CaLso) in the American continent, Europe, and New Zealand. The biological and genetic characteristics of the insect make its management difficult, and so do the high number of host, refuge. and feeding plants in which it can be found. Furthermore, the influence of climate change has caused psyllid populations to establish and colonize new areas and countries. At present, the psyllid vectors of microorganisms that cause diseases in plants are widely distributed, and studies are being carried out to understand the impact of their populations on intensive agricultural production systems. In the last decade, studies on the application of new biological control and management techniques have also increased aiming to count on fast and efficient alternatives for reducing the effects on crops and economy. A total of 74 scientific papers related to the host plants of these insect vectors, their biological and chemical control strategies, and the novel alternatives for their management were analysed. In order to maintain surveillance over the vector, the present status of the identification of these species in Cuba, the situation concerning the presence of the cultivation system. -psilid-CaLso in the world and the American and Caribbean regions, as well as the possible implications of the presence of these species for the Cuban agriculture were studied in depth. [ABSTRACT FROM AUTHOR]

Global food security could be threatened in the coming years by the emergence and spread of emerging pests in crops. Psyllids are considered as possible destructive pests due to their relationships with some important plant pathogens. Bactericera cockerelli Sulc (Hemiptera: Triozidae) is recognized as an efficient vector of the bacterium Candidatus Liberibacter solanacearum (CaLsol), an invasive pest according to the EPPO, which causes diseases in potatoes, tomatoes, peppers, and other solanaceous and some apiaceous crops. Known the vector-bacteria complex to be present in different countries of the world belonging to the American continent, Europe and New Zealand, 61 scientific papers related to this topic were reviewed. Changes in the climatic variables, the biological distribution of this insect-vector system, the high ecological plasticity that allows this insect to develop different biotypes, depending on the characteristics of the area where it develops, could complicate the control of the insect-pathogen system. These characteristics make necessary a maintained extreme surveillance in those countries where it is not yet present. So far, the bacterium and the vector are not present in Cuba; however, its proximity to countries where it is present, the existence of optimal climatic conditions host plants, and the increasing tourism and international trade, make necessary to offer updated information on this disease, the causal agents and their vectors as a contribution to the preparation of the scientific-technical-productive personnel and other decission makers. [ABSTRACT FROM AUTHOR]

" Candidatus Liberibacter solanacearum" (Lso) is a phloem-limited Gram-negative bacterium that infects crops worldwide. In North America, two haplotypes of Lso (LsoA and LsoB) are transmitted by the potato psyllid, Bactericera cockerelli (Šulc), in a circulative and persistent manner. Both haplotypes cause damaging plant diseases (e.g., zebra chip in potatoes). The psyllid gut is the first organ Lso encounters and could be a barrier for its transmission. However, little is known about the psyllid gut immune responses triggered upon Lso infection. In this study, we focused on the apoptotic response in the gut of adult potato psyllids at the early stage of Lso infection. We found that there was no evidence of apoptosis induced in the gut of the adult potato psyllids upon infection with either Lso haplotype based on microscopic observations. However, the expression of the inhibitor of apoptosis IAPP5.2 gene (survivin-like) was significantly upregulated during the period that Lso translocated into the gut cells. Interestingly, silencing of IAPP5.2 gene significantly upregulated the expression of two effector caspases and induced apoptosis in the psyllid gut cells. Moreover, RNA interference (RNAi) of IAPP5.2 significantly decreased the Lso titer in the gut of adult psyllids and reduced their transmission efficiency. Taken together, these observations suggest that Lso might repress the apoptotic response in the psyllid guts by inducing the anti-apoptotic gene IAPP5.2 at an early stage of the infection, which may favor Lso acquisition in the gut cells and facilitate its transmission by potato psyllid. [ABSTRACT FROM AUTHOR]

Zebra chip (ZC) disease caused by the bacterium 'Candidatus Liberibacter solanacearum' (Lso) and vectored by the potato psyllid (Bactericera cockerelli Šulc.) inflicts significant yield and quality losses in potato. Potato plants infected with Lso produce tubers with an internal brown stripe pattern that is unacceptable to the potato processing industry. Potato varieties tolerant of ZC disease could reduce yield and quality losses caused by the disease, as well as diminish insecticide usage to control potato psyllids. Tetraploid potato clones selected from breeding programs in the US were screened in Texas under both greenhouse and field conditions. Chipping quality in tubers harvested from plants infested with Lso-infected psyllids and those harvested from from non-infested plants were compared, and tuber symptoms associated with ZC disease were evaluated. Clones showing good chipping quality and promising ZC tolerance in the greenhouse and first field trials were independently tested in a second field trial. Clones of the A07781 and TX12484 families consistently showed good processing quality and ZC tolerance over multiple evaluations. These findings indicate that good processing clones with tolerance to ZC disease are available. These clones could be used by potato breeding programs as parents and could also be used to study the genetics of tolerance to ZC disease. [ABSTRACT FROM AUTHOR]

The potato/tomato psyllid Bactericera cockerelli causes serious damage to several solanaceous crops by direct feeding and vectoring Candidatus Liberibacter solanacearum, a bacterial pathogen. Electron beam (eBeam) irradiation is an environmentally friendly, chemical‐free alternative method that is increasing in use for disinfestation of insect pests. We hypothesize that this irradiation technology will have detrimental effects on potato psyllid and thus impede its disease vectoring. To this end, we explored the effects of eBeam treatment ranging from 50 to 500 Gy on survival, development and reproduction of this pest. Impact on psyllids was apparently dose‐dependent. When irradiated at 350 Gy, eggs could not hatch, 1st instar nymphs failed to emerge, and although a small portion of irradiated 5th instar nymphs survived, the emerged adults were mostly deformed. Abnormality in eclosed adults suggests harmful effects of eBeam on metamorphosis. Reproduction was seriously impaired when female psyllids were exposed to eBeam at the 5th instar nymphal or young adult stage, presumably due to inability to form oocytes. In addition, reciprocal crosses between irradiated and untreated psyllids indicated that female psyllids were more radiosensitive than males to eBeam. Taken together, these findings indicate that eBeam negatively impacted potato psyllid development and reproduction, which would inevitably compromise its disease transmission capacity. A dose of 350 Gy can be considered as a reference dose for effective control of potato psyllids. [ABSTRACT FROM AUTHOR]

The potato psyllid, Bactericera cockerelli (Šulc), is a major pest of potato (Solanum tuberosum L.; Solanales: Solanaceae) as a vector of ' Candidatus Liberibacter solanacearum', the pathogen that causes zebra chip. Management of zebra chip is challenging in part because the noncrop sources of Liberibacter-infected psyllids arriving in potato remain unknown. Adding to this challenge is the occurrence of distinct genetic haplotypes of both potato psyllid and Liberibacter that differ in host range. Longleaf groundcherry (Physalis longifolia Nutt.) has been substantially overlooked in prior research as a potential noncrop source of Liberibacter-infected B. cockerelli colonizing fields of potato. The objective of this study was to assess the suitability of P. longifolia to the three common haplotypes of B. cockerelli (central, western, and northwestern haplotypes), and to two haplotypes of ' Ca. L. solanacearum' (Liberibacter A and B haplotypes). Greenhouse bioassays indicated that B. cockerelli of all three haplotypes produced more offspring on P. longifolia than on potato and preferred P. longifolia over potato during settling and egg-laying activities. Greenhouse and field trials showed that P. longifolia was also highly susceptible to Liberibacter. Additionally, we discovered that infected rhizomes survived winter and produced infected plants in late spring that could then be available for psyllid colonization and pathogen acquisition. Results show that P. longifolia is susceptible to both B. cockerelli and ' Ca. L. solanacearum' and must be considered as a potentially important source of infective B. cockerelli colonizing potato fields in the western United States. [ABSTRACT FROM AUTHOR]

The bacterium 'Candidatus Liberibacter solanacearum' (Lso) is a phloem-restricted plant pathogen associated with different diseases worldwide. In North America, two haplotypes, LsoA and LsoB, are vectored by the potato psyllid, Bactericera cockerelli Šulc that causes zebra chip (ZC) in potato (Solanum tuberosum L.) and other solanaceous plants. In potato, both haplotypes cause similar symptoms albeit with different severities: LsoB-infected potato plants exhibit more severe ZC tuber symptoms compared to LsoA-infected plants. Previous research suggested that Lso-infected plants could produce viable seed tubers, potentially creating a reservoir for Lso propagation. The current study evaluated the effect of Lso haplotype on the emergence rate of tubers produced by infected potato plants (var. 'Atlantic') grown in the Lower Rio Grande area during the 2018 and 2019 growing seasons. Five Lso treatments were evaluated: uninfested controls, plants infested with uninfected psyllids (LsoFree), plants infested with LsoA- or LsoB-infected psyllids (LsoA and LsoB, respectively), and plants infested with psyllids co-infected with both Lso haplotypes (LsoAB). A portion of harvested tubers were evaluated for ZC symptom severity using a visual score. The remaining tubers were placed in cold storage for six months and then used as seed tubers to compare emergence and plant development rates among the treatments. This study confirms the previously reported differences in ZC symptom severity between Lso haplotypes. Furthermore, this study showed that tubers produced by Lso-infected plants were 90.1 ± 8.2% inviable. Importantly, all plants developing from these seed tubers tested negative for the presence of Lso. The results of this study suggest that while seed tubers produced by Lso-infected plants can germinate, the daughter plant was not infected by Lso. Therefore, Atlantic tubers produced by previously infected plants with Lso haplotypes A and B in South Texas do not represent a reservoir for Lso disease. [ABSTRACT FROM AUTHOR]

The impact of drought stress on tripartite plant‐pathogen‐vector interactions constitutes a complex and largely understudied field of plant‐insect interaction. A number of studies explored these topics using aphid vectors of plant pathogens, but few have considered the interactions between drought‐stressed plants and pathogen‐transmitting psyllids. The potato psyllid, Bactericera cockerelli (Šulc) (Hemiptera: Triozidae), is one of the key pests of solanaceous crops in the USA that causes direct injury as well as indirect injury through transmission of a bacterial pathogen, Candidatus Liberibacter solanacearum (Lso), the causal agent of zebra chip. Previous studies explored the impact of Lso infection and drought stress on B. cockerelli development and reproductive rate separately, but no research to date has evaluated whether drought stress and Lso infection alter feeding behavior of the insects. We explored this using the electrical penetration graph (EPG) technique and monitored feeding behavior of Lso‐infected and uninfected potato psyllids on well‐watered and drought‐stressed tomato (Solanum lycopersicum L., Solanaceae). We found that drought stress had a significant effect on feeding behavior associated with salivation into the phloem and phloem ingestion, both linked to Lso transmission. Furthermore, infected potato psyllids in particular produced a higher number of events associated with these feeding behaviors and remained in these phases longer in well‐watered plants than in plants that were under drought stress. We also reported a new and previously undescribed waveform H of unknown biological function that was produced by the psyllids. This is the first study that considered the impact of bacterial infection and concomitant drought stress on feeding behavior of an insect quantified using EPG. [ABSTRACT FROM AUTHOR]

"Candidatus Liberibacter solanacearum" (Lso) (="Candidatus Liberibacter psyllarous") is an uncultured, phloem-limited bacterium that is associated with zebra chip disease (ZC) in potato (Solanum tuberosum L.) and transmitted by the potato psyllid (Bactericera cockerelli (Šulc)). Vector density and timing of infection have been shown to affect ZC prevalence at harvest; however, little work has been done on disease development during storage. Here we confirm with field-cage trials that ZC prevalence at harvest was greater with increased time between inoculation and vine kill. Moreover, we show that with Pacific Northwest growing conditions, ZC can develop over time during storage. Plants inoculated 2 to 3 weeks before vine kill showed little or no ZC symptoms in tubers at harvest, but higher prevalence of symptoms after 3 months in storage. For plants inoculated at 4 to 5 weeks before vine kill, tubers exhibited notable symptoms at harvest, but still showed evidence of symptom development after storage. Plants inoculated within 1 week before vine kill exhibited little or no risk of ZC in tubers at harvest or after storage. Higher vector density tended to contribute to ZC prevalence, but was far less important than timing of infection. These results underscore the potential danger of underestimating ZC prevalence at harvest for tubers being stored long term, and suggest that plants at risk of Lso infection should be protected from potato psyllids until at least 2 weeks before vine kill. [ABSTRACT FROM AUTHOR]

The ectoparasitoid Tamarixia triozae is a promising biological control agent of the tomato psyllid, Bactericera cockerelli, based on its high parasitism rates on different crops. The parasitism, host feeding, and transgenerational effects (in terms of sex ratio) of T. triozae females exposed to three insecticides (soybean oil, imidacloprid, and abamectin) as eggs, larvae, and pupae were evaluated when a mixture of second, third, fourth, and fifth instars of the host B. cockerelli was offered. The concentrations bioassayed of each insecticide corresponded to the minimum field-registered concentration [MiFRC] and one-half the MiFRC. No parasitism of B. cockerelli second instars was recorded when parasitoid's females were exposed in any of the three immature stages to any of the insecticides. In contrast, in some cases, parasitism of T. triozae females treated as eggs, larvae, or pupae with soybean oil and imidacloprid was reduced in third, fourth, or fifth instar. In most cases, the host feeding was reduced in second and third instar of the host B. cockerelli when T. triozae females were treated as eggs, larvae, or pupae. Any insecticide modified the sex ratio in the F2 generation. In conclusion, both parasitism and host feeding were affected by the insecticides depending on the concentration and on the nymphal instar of the host B. cockerelli offered. [ABSTRACT FROM AUTHOR]

Insect abundance is commonly recorded in the form of discrete counts taken from plants. Analyses of these counts provide information about spatial distributions and population structure. A study was conducted in the Lower Rio Grande Valley of Texas during April and May 2014 to determine how populations of potato psyllids [ Bactericera cockerelli (Šulc)] within three potato fields change over time. It was found that potato psyllid populations in these potato fields frequently changed both spatially and temporally. Chi-square goodness of fit tests and Akaike's Information Criterion indicated that the frequency distributions of potato psyllid counts conformed to a negative binomial distribution, implying an aggregated spatial pattern. Variance–mean ratios were always much larger than one, also implying spatially clumped populations. However, with a few exceptions, a Spatial Analysis by Distance IndicEs analysis showed that potato psyllid counts were mostly random in space, the clumping generally occurring on individual potato plants and rarely involving groups of potato plants in close proximity. Trends in proportions of plants infested by at least one potato psyllid and the clumping parameter k were similar for all three potato fields. Potato psyllid spatial population structure is a dynamic process that involves continuous adult movements leading to substantial redistribution of potato psyllids over limited time spans of 2 to 3 d. By capturing elements of their spatial and temporal patterns of redistribution, the study reported here is a step towards a better understanding of the population dynamics and movement of potato psyllids. [ABSTRACT FROM AUTHOR]

Autophagy, also known as type II programmed cell death, is a cellular mechanism of “self-eating”. Autophagy plays an important role against pathogen infection in numerous organisms. Recently, it has been demonstrated that autophagy can be activated and even manipulated by plant viruses to facilitate their transmission within insect vectors. However, little is known about the role of autophagy in the interactions of insect vectors with plant bacterial pathogens. ‘Candidatus Liberibacter solanacearum’ (Lso) is a phloem-limited Gram-negative bacterium that infects crops worldwide. Two Lso haplotypes, LsoA and LsoB, are transmitted by the potato psyllid, Bactericera cockerelli and cause damaging diseases in solanaceous plants (e.g., zebra chip in potatoes). Both LsoA and LsoB are transmitted by the potato psyllid in a persistent circulative manner: they colonize and replicate within psyllid tissues. Following acquisition, the gut is the first organ Lso encounters and could be a barrier for transmission. In this study, we annotated autophagy-related genes (ATGs) from the potato psyllid transcriptome and evaluated their expression in response to Lso infection at the gut interface. In total, 19 ATGs belonging to 17 different families were identified. The comprehensive expression profile analysis revealed that the majority of the ATGs were regulated in the psyllid gut following the exposure or infection to each Lso haplotype, LsoA and LsoB, suggesting a potential role of autophagy in response to Lso at the psyllid gut interface.

Candidatus Liberibacter solanacearum (CaLso) is associated with diseases in tomato crops and transmitted by the tomato psyllid Bactericera cockerelli. A polymeric water-dispersible nanobactericide (PNB) was evaluated against CaLso as a different alternative. PNB is a well-defined polycationic diblock copolymer designed to permeate into the vascular system of plants. Its assessment under greenhouse conditions was carried out with tomato plants previously infected with CaLso. Using a concentration as low as 1.0 mg L−1, a small but significant reduction in the bacterial load was observed by real-time qPCR. Thus, to achieve an ecologically friendly dosage and set an optimum treatment protocol, we performed experiments to determine the effective concentration of PNB to reduce ~65% of the initial bacterial load. In a first bioassay, a 40- or 70-fold increase was used to reach that objective. At this concentration level, other bioassays were explored to determine the effect as a function of time. Surprisingly, a real reduction in the symptoms was observed after three weeks, and there was a significant decrease in the bacterial load level (~98%) compared to the untreated control plants. During this period, flowering and formation of tomato fruits were observed in plants treated with PNB.

'Candidatus Liberibacter solanacearum' is a plant pathogen affecting the families Solanaceae and Apiaceae in different parts of the world. 'Ca. L. solanacearum' is a Gram-negative, fastidious a-proteobacterium that is vectored by different psyllid species. Plant-pathogenic bacteria are known for interfering with the host physiology or defense mechanisms, often by secreting bacterial effectors. Effector proteins are critical for virulence; therefore, the identification of effectors could help with disease management. In this study, we characterized the Sec-translocondependent 'Ca. L. solanacearum'-hypothetical protein effector 1 (Lso- HPE1). We compared this protein sequence in the different 'Ca. L. solanacearum' haplotypes. We predicted the signal peptide and validated its function using Escherichia coli's alkaline phosphatase fusion assay. Agrobacterium tumefaciens-mediated transient expression in Nicotiana benthamiana demonstrated that Lso-HPE1 from 'Ca. L. solanacearum' haplotypes A and B were able to inhibit the induction of cell death in plants. We also compared gene expression of the Lso-HPE1- transcripts in 'Ca. L. solanacearum' haplotypes A and B in tomato and in the vector Bactericera cockerelli. This work validates the identification of a Sectranslocon- dependent 'Ca. L. solanacearum' protein possibly involved in suppression of plant cell death. [ABSTRACT FROM AUTHOR]

BACKGROUND: Tomato/potato psyllid (TPP), Bactericera cockerelli (Šulc), is a recently established invasive pest of solanaceous crops in New Zealand. No alternative control strategies are available against TPP due to the development of insecticidal resistance. We investigated the combined use of the predatory mites Amblydromalus limonicus or Neoseiulus cucumeris with either the fungus Beauveria bassiana (suspensions and dry conidia) or with Typha orientalis pollen as a control of TPP in greenhouse bell pepper over 7 weeks. RESULTS: All treatments significantly reduced TPP densities compared with the control. A. limonicus resulted in significantly lower TPP densities than any other combination with N. cucumeris. B. bassiana suspensions did not affect A. limonicus densities when they were combined. However, the application of dry B. bassiana conidia significantly reduced the densities of A. limonicus. The use of T. orientalis pollen resulted in significantly higher densities of A. limonicus but densities of N. cucumeris did not increase. The combined use of A. limonicus with B. bassiana suspensions or T. orientalis pollen resulted in significantly decreased TPP populations and greater crop yield. CONCLUSION: The synergistic application of A. limonicus with B. bassiana suspensions could be a suitable strategy to control TPP in the greenhouse. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Engytatus varians (Distant) (Hemiptera: Miridae) was observed to prey on eggs and nymphs of the tomato psyllid Bactericera cockerelli (Sulc.) (Hemiptera: Triozidae) on tomato plants, Solanum lycopersicum L., in Tarímbaro, Michoacán, Mexico, in 2014. In the present study, several growth parameters of this predator were assessed under three different diets (second-third [N2-N3] instars of B. cockerelli + eggs of the grain moth, Sitotroga cerealella Olivier [Lepidoptera: Gelechiidae] + 5% sugar solution; N2-N3 instars of B. cockerelli + S. cerealella eggs; and N2-N3 instars of B. cockerelli alone). In females, among the three diet groups, the group fed N2-N3 instars of B. cockerelli + S. cerealella eggs + 5% sugar solution showed the highest longevity (46.6 ± 2.4 days), probability of survival (100% up to day 26), fecundity (180.5 ± 8.5 eggs/female), oviposition rate (OR, 3.9 ± 0.2 eggs/female/day), intrinsic rate of increase (rm, 0.118 ± 0.0001/female/day), net reproductive rate (R0, 107.8 ± 0.2 female eggs/female), and mean generation time (T, 39.6 ± 0.01 days). Our results indicate that the sugar solution improved the physical conditions and population dynamics of E. varians and that sugar could be used to improve the rearing of this predator. [ABSTRACT FROM AUTHOR]

The tomato potato psyllid (TPP, Bactericera cockerelli) is an important vector of Candidatus Liberibacter solanacearum. TPP is a phloem sap feeder, with an extensive host plant range. Measuring host plant feeding via electrical penetration graph (EPG) is a potentially less time‐consuming method compared with traditional ways of assessing the host range of sap‐feeding insects through feeding bioassays. Feeding behaviour of Candidatus Liberibacter solanacearum‐positive adult TPP was measured using EPG technique on seven plant species: capsicum, eggplant, Cape gooseberry, poroporo, black nightshade (all Solanaceae), kumara (Convolvulaceae) and coprosma (Rubiaceae). Coprosma was used as a plant species of unknown host status. EPG data were analysed for three recording durations (5, 10 and 15 h). Data recorded for 10 h provided the most accurate prediction of subsequent feeding behaviour, allowing discrimination between host plants which could support feeding by TPP and non‐host plants that could not. EPG feeding behaviour was then contrasted with the survival of early life stages of TPP on four of the seven plant species under a choice situation on whole plants. The one discrepancy between the two methods for separating host from non‐host plants was with Cape gooseberry. EPG suggested that Cape gooseberry was as acceptable for feeding by TPP as capsicum, but whole‐plant assays showed survival of early nymph stages on Cape gooseberry was poor. EPG has merit as a tool for rapid assessment of plants at risk of feeding damage from a phloem sap feeder. However, a degree of experience is required to operate this technology successfully and to interpret the output data. The wire attachment on the insects may have a negative influence on initial plant contact. Therefore, a long recording time around 10 h may be required to offset this limitation. [ABSTRACT FROM AUTHOR]

BACKGROUND Predator–prey interactions consist of direct consumption of prey by predators and indirect non‐consumptive effects on prey. Predator cues can induce predation stress in prey that negatively influences the survival, development, reproduction, and feeding behaviour of the prey. This study evaluated the effects of hemipteran‐tending ant (Technomyrmex albipes) odour on the development, survival, reproduction, and predation rates of the predatory mite Amblydromalus limonicus when feeding on an invasive pest of solanaceous crops, Bactericera cockerelli. The age‐stage, two‐sex life table theory was used to compare the demographic characteristics and predation rates of A. limonicus in the presence and absence of ant odour. RESULTS: We show that exposure to ant odour did not alter the development, survival rate, and fecundity of A. limonicus, but induced a sexually dimorphic response in its longevity; consumption rates also showed that dimorphic response‐predation rates increased in female A. limonicus, but not in males. CONCLUSION: To our knowledge, this is the first report indicating increased consumption rates by natural enemies exposed to odour from a mutualist of pest (ant). This finding may provide new insights into understanding tri‐partite interaction involving a pest, its predator, and a mutulist of the pest. © 2018 Society of Chemical Industry This article discusses the interactions among a psyllid pest (Bactericera cockerelli), its predator (Amblydromalus limonicus), and its mutualist ant (Technomyrmex albipes), and shows that the ant odour did not affect the developmental time and reproduction of A. limonicus, but significantly increased the prey consumption rates of female A. limonicus. [ABSTRACT FROM AUTHOR]

The bacterial pathogen ‘Candidatus Liberibacter solanacearum’ (Lso) is transmitted by the tomato potato psyllid (TPP), Bactericera cockerelli, to solanaceous crops. In the present study, the changes in metabolic profiles of insect-susceptible (cv CastleMart) and resistant (RIL LA3952) tomato plants in response to TPP vectoring Lso or not, were examined after 48 h post infestation. Non-volatile and volatile metabolites were identified and quantified using headspace solid-phase microextraction equipped with a gas chromatograph-mass spectrometry (HS-SPME/GC-MS) and ultra-high pressure liquid chromatography coupled to electrospray quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-QTOFMS), respectively. Partial least squares-discriminant analysis (PLS-DA) was used to define the major uncorrelated metabolite components assuming the treatments as the correlated predictors. Metabolic changes in various classes of metabolites, including volatiles, hormones, and phenolics, were observed in resistant and susceptible plants in response to the insects carrying the pathogen or not. The results suggest the involvement of differentially regulated and, in some cases, implicates antagonistic metabolites in plant defensive signaling. Upon validation, the identified metabolites could be used as markers to screen and select breeding lines with enhanced resistance to reduce economic losses due to the TPP-Lso vector-pathogen complex in Solanaceous crops.

The tomato potato psyllid (TPP) is a serious pest of New Zealand glasshouse crops. This study examined the use of sticky traps in a glasshouse tomato crop to identify factors that influence TPP catches, with a view to developing a more consistent TPP monitoring system for use in IPM decision models. TPP catches were highest on yellow traps compared with black traps and white traps, and were greatest when traps were set near the glasshouse roof (2.1 m). Ultraviolet (UV) illumination substantially increased TPP catches on traps of all colours. There was considerable variation in TPP catch density within traps, especially near the edges. The results suggest that yellow sticky traps have good potential as TPP monitoring tools in glasshouse tomato crops. Consistency in TPP counts could be enhanced if traps were placed at constant height, were illuminated by UV, and assessments were limited to the trap centres. [ABSTRACT FROM AUTHOR]