Unusual outbreaks of curly top disease in processing tomato fields in northern California in 2021 and 2022 were caused by a rare strain of beet curly top virus and facilitated by extreme weather events.

In the western United States, curly top disease (CTD) is caused by beet curly top virus (BCTV). In California, CTD causes economic loss to processing tomato production in central and southern areas but, historically, not in the north. Here, we document unusual CTD outbreaks in processing tomato fields in the northern production area in 2021 and 2022, and show that these were caused by the rare spinach curly top strain (BCTV-SpCT). These outbreaks were associated with proximity of fields to foothills and unusually hot, dry, and windy spring weather conditions, possibly by altering migrations of the beet leafhopper (BLH) vector from locations with BCTV-SpCT reservoirs. Support for this hypothesis came from the failure to observe CTD outbreaks and BLH migrations in 2023, when spring weather conditions were cool and wet. Our results show the climate-induced emergence of a rare plant virus strain to cause an economically important disease in a new crop and location.

Abnormal cell wall structure caused by boron nutrient imbalance in orchards could affect psyllid feeding behaviour, resulting in epidemic variation of Asian citrus psyllid.

The control of Huanglongbing (HLB), one of the most destructive pests of citrus, relies heavily on the reduction of Asian citrus psyllid (ACP), Diaphorina citri Kuwayama. An in-depth understanding of ACP feeding behaviours among citrus plants is urgent for comprehensive management of orchards. An investigation was conducted in 37 citrus orchards in HLB epidemic areas, sampling shoots in the area with aggregation feeding of ACP (ACPf) and shoots in a neighbouring area without ACP feeding (CK), to study the interaction between leaf chemical composition and ACP psyllid feeding behaviours. Results of FTIR showed a strong absorption peak intensity, mainly representing functional groups originating from cell wall components in the leaf with ACP feeding. As compared with the control, cell wall components, such as alkali-soluble pectin, water-soluble pectin, total soluble pectin, cellulose, and hemicellulose, of the cell wall of ACPf increased by 134.0%, 14.0%, 18.0%, 12.5%, and 20.35%, respectively. These results suggest that cell wall mechanical properties significantly decreased in the term of decreases in pectin performance and cellulose mechanical properties. In addition, there was a remarkably lower boron (B) content in leaves and cell wall components with ACP feeding. Further analysis indicated that leaf B content significantly affected leaf cell wall components. Taken together, we provide evidence to demonstrate that the regional distribution of nutrient imbalance in orchards could affect psyllid feeding behaviour by weakening the cell wall structure, resulting in epidemic variation in ACP. This could help us to understand the management of psyllid infections in orchards with unbalanced nutrition.

Silencing of Glutamine: Fructose-6-Phosphate Aminotransferase Impairs Growth and Development in Sogatella furcifera (Hemiptera: Delphacidae).

Glutamine: fructose-6-phosphate aminotransferase (GFAT), the fourth enzyme in the chitin synthesis pathway, exerts wide-ranging effects on the growth and development of organisms. However, the role of GFAT in Sogatella furcifera remains unknown. In this study, the functional significance of the GFAT gene of S. furcifera was analyzed using a reverse transcription-polymerase chain reaction and RNA interference (RNAi) analyses. The complementary DNA sequence of SfGFAT was 3162 bp in length and contained a 2067 bp open reading frame encoding 688 amino acid residues. Structural domain analysis indicated that the SfGFAT protein consisted of one glutamine aminotransferase class 2 domain and two sugar isomerase domains. Expression profile analysis revealed that SfGFAT was expressed throughout the egg, nymph, and adult phases and was strongly expressed on the first day of each nymph stage and in the integuments of five tissues. RNAi results revealed that SfGFAT gene silencing significantly inhibited the mRNA expression of the target gene and resulted in severe mortality among S. furcifera. In summary, these findings demonstrate that SfGFAT plays a critical role in the development of S. furcifera. Moreover, these results may aid in the development of methods to control the spread of S. furcifera.

Comparative Metabolomic Analysis Reveals the Differences in Nonvolatile and Volatile Metabolites and Their Quality Characteristics in Beauty Tea with Different Extents of Punctured Leaves by Tea Green Leafhopper.

The fresh leaves were processed into beauty tea from the Camellia sinensis "Jinxuan" cultivar, which were punctured by tea green leafhoppers to different extents. Low-puncturing dry tea (LPDT) exhibited a superior quality. Altogether, 101 and 129 differential metabolites, including tea polyphenols, lipids, and saccharides, were identified from the fresh leaves and dry beauty tea, respectively. Most metabolite levels increased in the fresh leaves punctured by leafhoppers, but the opposite was observed for the dry beauty tea. According to relative odor activity values (rOAVs) and partial least-squares discriminant analysis (PLS-DA), four characteristic volatiles, including linalool, geraniol, benzeneacetaldehyde, and dihydrolinalool, were selected. Mechanical injury to leaves caused by leafhoppers, watery saliva secreted by the leafhopper, and different water contents of the fresh leaves in different puncturing degrees are the possible reasons for the difference in the quality of the beauty tea with different levels of puncturing. Overall, this study identified a wide range of chemicals that are affected by the degrees of leafhopper puncturing.

Edible and Medicinal Progress of Cryptotympana atrata (Fabricius) in China.

As an important resource insect, the Cryptotympana atrata is widely distributed in the eastern and central parts of China. The cicada slough is one of the traditional crude drugs in East Asia, and the main component is polysaccharide, which has the functions of anti-convulsion, relieving asthma and improving lipid metabolism. The parasitoid fungus Cordyceps cicadae, which grows inside the cicada nymphs and forms the fruiting bodies on the surface of the host's carcass, is also known as the "cicada flower" in China. The Cordyceps cicadae is another old, traditional Chinese medicine, which has been used as a tonic and medicine to nourish and regulate human immunity for centuries. For the further development and utilization of the golden cicada, this paper summarized the C. atrata from the aspects of their biological characteristics, distribution area, life cycle, history of edible and medicinal use, edible methods and nutritional compositions; emphatically introduced the edible and potential medicinal value of the C. atrata; and specifically expounded the research progress of its application. As one popular insect food, the prospects for the development of C. atrata have also been put forward, especially in artificial breeding technology, food safety risk assessment and medicinal value utilization.

Nutrient supplementation by genome-eroded Burkholderia symbionts of scale insects.

Hemipterans are known as hosts to bacterial or fungal symbionts that supplement their unbalanced diet with essential nutrients. Among them, scale insects (Coccomorpha) are characterized by a particularly large diversity of symbiotic systems. Here, using microscopic and genomic approaches, we functionally characterized the symbionts of two scale insects belonging to the Eriococcidae family, Acanthococcus aceris and Gossyparia spuria. These species host Burkholderia bacteria that are localized in the cytoplasm of the fat body cells. Metagenome sequencing revealed very similar and highly reduced genomes (<900KBp) with a low GC content (~38%), making them the smallest and most AT-biased Burkholderia genomes yet sequenced. In their eroded genomes, both symbionts retain biosynthetic pathways for the essential amino acids leucine, isoleucine, valine, threonine, lysine, arginine, histidine, phenylalanine, and precursors for the semi-essential amino acid tyrosine, as well as the cobalamin-dependent methionine synthase MetH. A tryptophan biosynthesis pathway is conserved in the symbiont of G. spuria, but appeared pseudogenized in A. aceris, suggesting differential availability of tryptophan in the two host species' diets. In addition to the pathways for essential amino acid biosynthesis, both symbionts maintain biosynthetic pathways for multiple cofactors, including riboflavin, cobalamin, thiamine, and folate. The localization of Burkholderia symbionts and their genome traits indicate that the symbiosis between Burkholderia and eriococcids is younger than other hemipteran symbioses, but is functionally convergent. Our results add to the emerging picture of dynamic symbiont replacements in sap-sucking Hemiptera and highlight Burkholderia as widespread and versatile intra- and extracellular symbionts of animals, plants, and fungi.

Coupled Oscillators in an Agroecosystem: Integrating Direct and Indirect Effects.

AbstractAgricultural pests are increasingly appreciated as subjects of ecology. One particular case, a pest in coffee production, is analyzed here using the conceptual framework of complex systems, increasingly acknowledged as having an obvious home in the field of ecology, notorious for its complex structures. The particular case analyzed here arguably falls under the control of the complexity of the ecological system rather than of a simple magic bullet of population regulation. The system, which has been under study in southern Mexico for the past quarter century, is analyzed through the lens of neutral oscillations of the classical nondissipative Lotka-Volterra system. Based on three consumer/resource pairs (populations of [1] an ant, [2] a scale insect, [3] a beetle predator of the scale insect, [4] a fungal pathogen of the scale insect, and [5] a fly parasitoid of the ant), this five-dimensional system is well known qualitatively. Coupling all agents through both direct effects and trait-mediated indirect effects, the behavior of the neutral oscillation form of the system reveals a complex set of behaviors, including harmonized invariant sets, chaos, and/or quasiperiodicity. Such behaviors are well-known subjects in the science of complex systems and, it is argued, are ultimately sufficient to effect a degree of regulation on the pest, independent of explicit density-dependent feedback. Control of the system is thus seen as arguably actuated through its complexity, independent of any classic dissipative force.

Potato psyllids mount distinct gut responses against two different 'Candidatus Liberibacter solanacearum' haplotypes.

'Candidatus Liberibacter solanacearum' (Lso) is a bacterial pathogen infecting several crops and causing damaging diseases. Several Lso haplotypes have been identified. Among the seven haplotypes present in North America, LsoA and LsoB are transmitted by the potato psyllid, Bactericera cockerelli (Sulc), in a circulative and persistent manner. The gut, which is the first organ pathogen encounters, could be a barrier for Lso transmission. However, the molecular interactions between Lso and the psyllid vector at the gut interface remain largely unknown. In this study, we investigated the global transcriptional responses of the adult psyllid gut upon infection with two Lso haplotypes (LsoA and LsoB) using Illumina sequencing. The results showed that each haplotype triggers a unique transcriptional response, with most of the distinct genes elicited by the highly virulent LsoB. The differentially expressed genes were mainly associated with digestion and metabolism, stress response, immunity, detoxification as well as cell proliferation and epithelium renewal. Importantly, distinct immune pathways were triggered by LsoA and LsoB in the gut of the potato psyllid. The information in this study will provide an understanding of the molecular basis of the interactions between the potato psyllid gut and Lso, which may lead to the discovery of novel molecular targets for the control of these pathogens.

The role of insect intestinal microbes in controlling of Empoasca onukii Matsuda (Hemiptera: Cicadellidae) pest infestations in the production of tea garden: a review.

Pests like the phytophagous bug Empoasca onukii Matsuda frequently harm tea plants. The harm this insect does to agricultural and environmentally sensitive places is extremely harmful since physical and chemical prevention and control are still the primary methods of handling it. Therefore, it is important to develop pest management strategies. Recent research has demonstrated that pathogenic fungus and the gut microbiota interact to induce host and death, and that the gut microbiota, which has a dramatic effect on the host, can engage in pest control. The advancement of genome editing technologies is also new to the field of pest management. The diversity, function, and research methodologies of insect gut microbiota are summarized in this work, and discusses E. onukii Matsuda control options as well as the importance of insect gut microbiome in pest management. In comparison to traditional pesticides and physical prevention and control, the interaction between pathogenic fungi represented by Beauveria bassiana and intestinal microorganisms, as well as their participation in pest management, causes physiological stress on the host, which meets the new requirements of modern agricultural green development and has a protective effect on habitat fragmentation areas (Karst region). Exploring additional harmful fungus for pest management and fully using the specific traits of insect gut microbiota to achieve "killing insects with bacteria" would be a promising technique from this standpoint.

The impact of selenium on insects.

Selenium, a naturally occurring metalloid, is an essential trace element for many higher organisms, including humans. Humans primarily become exposed to selenium by ingesting food products containing trace amounts of selenium compounds. Although essential in these small amounts, selenium exhibits toxic effects at higher doses. Previous studies investigating the effects on insects of order Blattodea, Coleoptera, Diptera, Ephemeroptera, Hemiptera, Hymenoptera, Lepidoptera, Odonata, and Orthoptera revealed impacts on mortality, growth, development, and behavior. Nearly every study examining selenium toxicity has shown that insects are negatively affected by exposure to selenium in their food. However, there were no clear patterns of toxicity between insect orders or similarities between insect species within families. At this time, the potential for control will need to be determined on a species-by-species basis. We suspect that the multiple modes of action, including mutation-inducing modification of important amino acids as well as impacts on microbiome composition, influence this variability. There are relatively few studies that have examined the potential effects of selenium on beneficial insects, and the results have ranged from increased predation (a strong positive effect) to toxicity resulting in reduced population growth or even the effective elimination of the natural enemies (more common negative effects). As a result, in those pest systems where selenium use is contemplated, additional research may be necessary to ascertain if selenium use is compatible with key biological control agents. This review explores selenium as a potential insecticide and possible future directions for research.

Tea green leafhopper-induced synomone attracts the egg parasitoids, mymarids to suppress the leafhopper.

BACKGROUND: The tea green leafhopper, Empoasca flavescens is the most important pest of tea plants in China. Mymarid attractants based on herbivore-induced plant volatiles (HIPVs) from leafhopper feeding and oviposition-induced plant volatiles (OIPVs) were formulated and tested as a novel pest control agent against the leafhopper in tea plantations. RESULTS: Results showed that two mymarid species, Stethynium empoascae and Schizophragma parvula, had a reducing effect on leafhopper populations. The HIPVs and OIPVs were identified and bioassayed to screen the key synomones showing strong attraction to the mymarids. They were formulated into different blends, of which Field Attractant 1, comprising linalool, methyl salicylate, (E)-2-hexenal, perillen and α-farnesene at ratio of 1:2:3:58:146 (20 mg/lure), showed the strongest attraction to the mymarids. In field trials with the attractant, the average parasitism rate (60.46 ± 23.71%) of tea leafhoppers by the two mymarids in the attractant-baited area was significantly higher than that (42.85 ± 19.24%) in the CK area. Also, the average leafhopper density (46 ± 30 per 80 tea shoots) in the attractant-baited area was significantly lower than that (110 ± 70 per 80 tea shoots) in the CK area. CONCLUSION: This study showed that a synthetic blend of key volatiles from HIPVs and OIPVs at an optimal ratio can be formulated into an attractant with the potential to attract and retain wild mymarid populations to suppress leafhopper populations in infested tea plantations, so as to reduce or avoid the spraying of insecticides. © 2023 Society of Chemical Industry.

Induction of Glandular Trichomes to Control Bemisia tabaci in Tomato Crops: Modulation by the Natural Enemy Nesidiocoris tenuis.

Whitefly-transmitted viruses are one of the biggest threats to tomato (Solanum lycopersicum) growing worldwide. Strategies based on the introgression of resistance traits from wild relatives are promoted to control tomato pests and diseases. Recently, a trichome-based resistance characterizing the wild species Solanum pimpinellifolium was introgressed into a cultivated tomato. An advanced backcross line (BC5S2) exhibiting the presence of acylsugar-associated type IV trichomes, which are lacking in cultivated tomatoes, was effective at controlling whiteflies (Hemiptera: Aleyrodidae) and limiting the spread of whitefly-transmitted viruses. However, at early growth stages, type IV trichome density and acylsugar production are limited; thus, protection against whiteflies and whitefly-transmitted viruses remains irrelevant. In this work, we demonstrate that young BC5S2 tomato plants feeding-punctured by the zoophytophagous predator Nesidiocoris tenuis (Hemiptera: Miridae) displayed an increase (above 50%) in type IV trichome density. Acylsugar production was consistently increased in N. tenuis-punctured BC5S2 plants, which was more likely associated with upregulated expression of the BCKD-E2 gene related to acylsugar biosynthesis. In addition, the infestation of BC5S2 plants with N. tenuis effectively induced the expression of defensive genes involved in the jasmonic acid signaling pathway, resulting in strong repellence to Bemisia tabaci and attractiveness to N. tenuis. Thus, through preplant release of N. tenuis in tomato nurseries carried out in some integrated pest management programs, type IV trichome-expressing plants can be prepared to control whiteflies and whitefly-transmitted viruses at early growth stages. This study emphasizes the advantage of reinforcing constitutive resistance using defense inducers to guarantee robust protection against pests and transmitted viruses.

A bacteriocyte symbiont determines whitefly sex ratio by regulating mitochondrial function.

Nutritional symbionts influence host reproduction, but the underlying molecular mechanisms are largely unclear. We previously found that the bacteriocyte symbiont Hamiltonella impacts the sex ratio of the whitefly Bemisia tabaci. Hamiltonella synthesizes folate by cooperation with the whitefly. Folate deficiency by Hamiltonella elimination or whitefly gene silencing distorted whitefly sex ratio, and folate supplementation restored the sex ratio. Hamiltonella deficiency or gene silencing altered histone H3 lysine 9 trimethylation (H3K9me3) level, which was restored by folate supplementation. Genome-wide chromatin immunoprecipitation-seq analysis of H3K9me3 indicated mitochondrial dysfunction in symbiont-deficient whiteflies. Hamiltonella deficiency compromised mitochondrial quality of whitefly ovaries. Repressing ovary mitochondrial function led to distorted whitefly sex ratio. These findings indicate that the symbiont-derived folate regulates host histone methylation modifications, which thereby impacts ovary mitochondrial function, and finally determines host sex ratio. Our study suggests that a nutritional symbiont can regulate animal reproduction in a way that differs from reproductive manipulators.

Inoculation of Tomato With Plant Growth Promoting Rhizobacteria Affects the Tomato-Potato Psyllid-Candidatus Liberibacter Solanacearum Interactions.

The Rio Grande Valley (RGV) in southern Texas is well-suited for vegetable production due to its relatively mild/warm weather conditions in the fall and winter. Consequently, insects inflict year-round, persistent damage to crops in the RGV and regions with similar climate. Bactericera cockerelli (Sulc) (Hemiptera: Triozidae), commonly known as the potato psyllid, is a known vector of Candidatus Liberibacter solanacearum (CLso) (Hyphomicrobiales: Rhizobiaceae), a fastidious phloem-limited bacterium associated to vein-greening in tomatoes and Zebra Chip in potatoes. Vector control is the primary approach of integrated pest management (IPM) strategies that aim to prevent plant diseases in commercial agricultural systems. However, resistance-selective pressures that decrease the effectiveness of chemical control (insecticide) applications over time are of increasing concern. Therefore, we explore an ecological approach to devising alternative IPM methodologies to manage the psyllid-transmitted CLso pathogen to supplement existing chemical products and application schedules without increasing resistance. In this study, our objective was to examine the effects of plant-growth promoting rhizobacteria (PGPR) on host-vector-pathogen interactions. Soil-drench applications of PGPRs to Solanum lycopersicum (Solanales: Solanaceae) seedlings revealed structural and possible physiological changes to the plant host and indirect changes on psyllid behavior: host plants had increased length and biomass of roots and exhibited delayed colonization by CLso, while psyllids displayed changes in parental (F0) psyllid behavior (orientation and oviposition) in response to treated hosts and in the sex ratio of their progeny (F1). Based on our results, we suggest that PGPR may have practical use in commercial tomato production.

Epidemiological role of novel and already known 'Ca. P. solani' cixiid vectors in rubbery taproot disease of sugar beet in Serbia.

Rubbery taproot disease (RTD) of sugar beet was recently associated with the plant pathogenic bacterium 'Candidatus Phytoplasma solani' (CaPsol) and reported throughout the Pannonian Plain with variations in severity. Tracing CaPsol epidemiological pathways was performed in the experimental sugar beet field in Rimski Sancevi (Serbia) in 2020-2021, where an RTD outbreak was recently recorded. A molecular epidemiology approach was applied to the study of three RTD occurrence scenarios: epidemic, non-epidemic and 'absence of RTD'. As a result, Hyalesthes obsoletus ex Convolvulus arvensis was detected as a CaPsol vector to sugar beet, while two other cixiids were identified for the first time as vectors of the CaPsol-induced plant disease in crops: Reptalus quinquecostatus and R. cuspidatus. R. quinquecostatus was proposed culpable for the 2020 RTD epidemic outbreak in Rimski Sancevi when dSTOLg CaPsol strain predominated in the RTD-affected sugar beet, whereas R. cuspidatus had a negligible role in RTD occurrence and displayed ambiguous involvement in CaPsol epidemiology on a wider scale. The temporal discrepancy of the offset of CaPsol dissemination and disease occurrence is the main obstacle in predicting CaPsol-induced diseases. Predicting disease occurrence and severity can only be achieved by gaining a better understanding of CaPsol epidemiological pathways and insect vectors involved in disease outbreaks.

Acquisition and Transmission of 'Candidatus Liberibacter solanacearum' Differs Among Wolbachia-Infected and -Uninfected Haplotypes of Bactericera cockerelli.

'Candidatus Liberibacter solanacearum' (Lso) causes disease symptoms and economic losses in potato, tomato, and other solanaceous crops in North America. Lso is transmitted to plants by the potato psyllid, Bactericera cockerelli, which occurs as distinct haplotypes named western, central, and northwestern that differ in the presence or absence of the bacterial endosymbiont, Wolbachia. Previous work showed that all three vector haplotypes can transmit Lso, but it was not clear whether acquisition and transmission rates of Lso were equal among the haplotypes. The goal of our study was to compare Lso infection rates among psyllids of the western, central, and northwestern haplotypes. Using data collected from several years of periodic testing of Lso infection of laboratory-reared potato psyllid colonies, we showed that psyllids of the western and central haplotypes are more likely to harbor Lso than are psyllids of the northwestern haplotype. We then used greenhouse assays to demonstrate that psyllids of the northwestern haplotype are less likely to acquire and transmit Lso than those of the western haplotype. Lso infection rates corresponded with Wolbachia infection among the three psyllid haplotypes. The Wolbachia-infected central and western haplotypes were more likely to harbor and transmit Lso than the Wolbachia-free northwestern haplotype. Results demonstrate that potato psyllids of the western and central haplotypes pose a greater risk for spread of Lso in crops and suggest a pattern between infection with Lso and Wolbachia in potato psyllid.

Quantification of the effect of host patch configuration on the abundance of Bemisia tabaci in central Argentina: a multimodel inference approach.

Bemisia tabaci is a complex of species, which is considered the most common and important pest of a wide range of crops belonging to many different botanical families. In Argentina, this species is recognized as a vector of geminiviruses, and Middle East-Asia Minor 1, Mediterranean, New World and New World 2 have been found to coexist in the same area. Landscape elements, like habitat patch area and isolation, define the habitat configuration and have a direct effect on insect populations between and within host patches. In this paper, we analyse the effect of potato patch configuration on the distribution and abundance of B. tabaci. Potato patches were identified using Landsat TM5 and TM7 images, and a supervised classification was performed to quantify the spatial distribution of the patches in the whole study area. Potato patch metrics were estimated using Fragstats 4.4. Generalized linear mixed models were employed to analyse the relationship between whiteflies and landscape configuration, through a multimodel inference approach, finding that B. tabaci abundance and landscape metrics were very variable. After a multimodel selection process, we found that perimeter-to-area ratio and Euclidean distance between patches were the variables that best explained whitefly abundance in potato patches. Implications of these findings are discussed.

Potential of variegated lady beetle Hippodamia variegata in management of invasive tomato potato psyllid Bactericera cockerelli.

BACKGROUND: The tomato potato psyllid, Bactericera cockerelli (Sulc) is a new invasive pest in Western Australia, which may disperse across the whole of Australia within a few years and cause significant economic losses. Chemical control is the most widely used approach to manage B. cockerelli, but insect resistance, chemical residue and effects on non-target species have become an increasing concerned. Therefore, in this study, the biocontrol potential of variegated lady beetle, Hippodamia variegata (Goeze) was investigated. The impact of utilizing B. cockerelli as a food source on the predator's development and reproduction was assessed by formulating age-stage, two sex life tables. The predatory potential of H. variegata on B. cockerelli nymphs was assessed in a closed arena and the effects of releasing H. variegata for the control of B. cockerelli were then evaluated. RESULTS: H. variegata could successfully develop and oviposit when feeding on B. cockerelli. However, both survival and the rate of development were higher for H. variegata feeding on Myzus persicae (Sulzer) than B. cockerelli or a mixed population of B. cockerelli and M. persicae. A type II functional response was observed for H. variegata. In the greenhouse, the releases of H. variegata larvae reduced the number of B. cockerelli nymphs by up to 66% and adults by up to 59%, which positively influenced the plant chlorophyll content and biomass. CONCLUSIONS: This study demonstrated the potential of the resident generalist predator, H. variegata as a biocontrol agent for the invasive pest, B. cockerelli, which may help improving current management strategies. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Association of Two Bactericera Species (Hemiptera: Triozidae) With Native Lycium spp. (Solanales: Solanaceae) in the Potato Growing Regions of the Rio Grande Valley of Texas.

Bactericera cockerelli (Sulc) (Hemiptera: Triozidae) is a vector of 'Candidatus Liberibacter solanacearum' (Lso), the pathogen that causes potato zebra chip. Zebra chip incidence varies regionally, perhaps because of geographic differences in species of noncrop hosts available to the vector and in susceptibility of those hosts to Lso. Native and introduced species of Lycium (Solanales: Solanaceae) are important noncrop hosts of B. cockerelli in some regions of North America. Susceptibility of native Lycium species to Lso is uncertain. We investigated the use of two native species of Lycium by B. cockerelli in South Texas and tested whether they are susceptible to Lso. Bactericera cockerelli adults and nymphs were collected frequently from L. berlandieri Dunal and L. carolinianum Walter. Greenhouse assays confirmed that B. cockerelli develops on both species and showed that Lso infects L. carolinianum. Molecular gut content analysis provided evidence that B. cockerelli adults disperse between potato and Lycium. These results demonstrate that L. berlandieri and L. carolinianum are likely noncrop sources of potato-colonizing B. cockerelli in South Texas and that L. carolinianum is a potential source of Lso-infected psyllids. We also routinely collected the congeneric psyllid, Bactericera dorsalis (Crawford), from both Lycium species. These records are the first for this psyllid in Texas. Bactericera dorsalis completed development on both native Lycium species, albeit with high rates of mortality on L. berlandieri. B. dorsalis acquired and transmitted Lso on L. carolinianum under greenhouse conditions but did not transmit Lso to potato. These results document a previously unknown vector of Lso.

Foliar Antibiotic Treatment Reduces Candidatus Liberibacter asiaticus Acquisition by the Asian Citrus Psyllid, Diaphorina citri (Hemiptera: Liviidae), but Does not Reduce Tree Infection Rate.

Huanglongbing (HLB), or citrus greening, is the most destructive disease of cultivated citrus worldwide. Candidatus Liberibacter asiaticus (CLas), the putative causal agent of HLB, is transmitted by the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae). In Florida, D. citri was first reported in 1998, and CLas was confirmed in 2005. Management of HLB relies on the use of insecticides to reduce vector populations. In 2016, antibiotics were approved to manage CLas infection in citrus. Diaphorina citri is host to several bacterial endosymbionts and reducing endosymbiont abundance is known to cause a corresponding reduction in host fitness. We hypothesized that applications of oxytetracycline and streptomycin would reduce: CLas populations in young and mature citrus trees, CLas acquisition by D. citri, and D. citri abundance. Our results indicate that treatment of citrus with oxytetracycline and streptomycin reduced acquisition of CLas by D. citri adults and emerging F1 nymphs as compared with that observed in trees treated only with insecticides, but not with antibiotics. However, under field conditions, neither antibiotic treatment frequency tested affected CLas infection of young or mature trees as compared with insecticide treatment alone (negative control); whereas trees enveloped with mesh screening that excluded vectors did prevent bacterial infection (positive control). Populations of D. citri were not consistently affected by antibiotic treatment under field conditions, as compared with an insecticide only comparison. Collectively, our results suggest that while foliar application of oxytetracycline and streptomycin to citrus reduces acquisition of CLas bacteria by the vector, even high frequency applications of these formulations under field conditions do not prevent or reduce tree infection.