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Journal articles on the topic 'Sharpshooter vectors'

Author: Grafiati

Published: 4 June 2021

Last updated: 7 February 2022

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Backus, Elaine A., and David J. W. Morgan. "Spatiotemporal Colonization of Xylella fastidiosa in its Vector Supports the Role of Egestion in the Inoculation Mechanism of Foregut-Borne Plant Pathogens." Phytopathology® 101, no. 8 (2011): 912–22. http://dx.doi.org/10.1094/phyto-09-10-0231.

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The pathogen that causes Pierce's disease of grapevine, Xylella fastidiosa, is the only known bacterial, arthropod-transmitted plant pathogen that does not circulate in the vector's hemolymph. Instead, bacteria are foregut-borne, persistent in adult vectors but semipersistent in immatures (i.e., bacteria colonize cuticular surfaces of the anterior foregut, are retained for hours to days, but are lost during molting). Yet, exactly how a sharpshooter vector inoculates bacteria from foregut acquisition sites is unknown. The present study used confocal laser-scanning microscopy to identify locations in undissected, anterior foreguts of the glassy-winged sharpshooter colonized by green fluorescent protein-expressing X. fastidiosa. Spatial and temporal distributions of colonizing X. fastidiosa were examined daily over acquisition access periods of 1 to 6 days for both contaminated field-collected and clean laboratory-reared Homalodisca vitripennis. Results provide the first direct, empirical evidence that established populations of X. fastidiosa can disappear from vector foreguts over time. When combined with existing knowledge on behavior, physiology, and functional anatomy of sharpshooter feeding, present results support the idea that the disappearance is caused by outward fluid flow (egestion) not inward flow (ingestion) (i.e., swallowing). Thus, results support the hypothesis that egestion is a critical part of the X. fastidiosa inoculation mechanism. Furthermore, results suggest a cyclical, spatiotemporal pattern of microbial colonization, disappearance, and recolonization in the precibarium. Colonization patterns also support two types of egestion, termed rinsing and discharging egestion herein. Finally, comparison of acquisition results for field-collected versus laboratory-reared sharpshooters suggest that there may be competitive binding for optimum acquisition sites in the foregut. Therefore, successful inoculation of X. fastidiosa may depend, in large part, on vector load in the precibarium.

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Krugner, Rodrigo, Mark S. Sisterson, Jianchi Chen, Drake C. Stenger, and Marshall W. Johnson. "Evaluation of Olive as a Host of Xylella fastidiosa and Associated Sharpshooter Vectors." Plant Disease 98, no. 9 (2014): 1186–93. http://dx.doi.org/10.1094/pdis-01-14-0014-re.

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Olive (Olea europaea) trees exhibiting leaf scorch or branch dieback symptoms in California were surveyed for the xylem-limited, fastidious bacterium Xylella fastidiosa. Only approximately 17% of diseased trees tested positive for X. fastidiosa by polymerase chain reaction, and disease symptoms could not be attributed to X. fastidiosa infection of olive in greenhouse pathogenicity assays. Six strains of X. fastidiosa were isolated from olive in Southern California. Molecular assays identified strains recovered from olive as belonging to X. fastidiosa subsp. multiplex. Pathogenicity testing of olive strains on grapevine and almond confirmed that X. fastidiosa strains isolated from olive yield disease phenotypes on almond and grapevine typical of those expected for subsp. multiplex. Mechanical inoculation of X. fastidiosa olive strains to olive resulted in infection at low efficiency but infections remained asymptomatic and tended to be self-limiting. Vector transmission assays demonstrated that glassy-winged sharpshooter (Homalodisca vitripennis) could transmit strains of both subspp. multiplex and fastidiosa to olive at low efficiency. Insect trapping data indicated that two vectors of X. fastidiosa, glassy-winged sharpshooter and green sharpshooter (Draeculacephala minerva), were active in olive orchards. Collectively, the data indicate that X. fastidiosa did not cause olive leaf scorch or branch dieback but olive may contribute to the epidemiology of X. fastidiosa-elicited diseases in California. Olive may serve as an alternative, albeit suboptimal, host of X. fastidiosa. Olive also may be a refuge where sharpshooter vectors evade intensive areawide insecticide treatment of citrus, the primary control method used in California to limit glassy-winged sharpshooter populations and, indirectly, epidemics of Pierce's disease of grapevine.

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Sanderlin, R. S., and R. A. Melanson. "Insect Transmission of Xylella fastidiosa to Pecan." Plant Disease 94, no. 4 (2010): 465–70. http://dx.doi.org/10.1094/pdis-94-4-0465.

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Pecan bacterial leaf scorch (PBLS), caused by the bacterium Xylella fastidiosa, can cause economically significant crop loss to some pecan (Carya illinoinensis) cultivars in the southeastern United States. X. fastidiosa is typically vectored by spittlebugs (Cercopidae) and leafhoppers (Cicadellidae). Because no vector species had been reported for pecan, an attempt was made to identify potential vectors that are capable of acquiring the bacterium from infected pecan trees and transmitting to pecan. Several spittlebug and leafhopper species collected from various sources, including sorghum and pecan, were tested as potential vectors of the pathogen from pecan to pecan. When tested in groups, the pecan spittlebug, Clastoptera achatina; the Johnson-grass sharpshooter, Homalodisca insolita; and the glassy-winged sharpshooter (GWSS), Homalodisca vitripennis, had transmission rates to pecan of 11.4, 19.3, and 4%, respectively, following a pathogen acquisition period on infected pecan terminals. The pecan spittlebug is common in pecan orchards in the southeastern United States, and the GWSS was observed on young vigorous pecan shoots. Limited testing with the diamond-backed spittlebug, Lepyronia quadrangularis, and the lateral-lined sharpshooter, Cuerna costalis, suggested that these could be occasional vectors of X. fastidiosa to pecan. There is a need for studies on the identification and population dynamics of Cicadellidae that inhabit pecan orchards to determine if management of vectors is needed in commercial pecan production to reduce the spread of PBLS.

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Baccari, Clelia, Nabil Killiny, Michael Ionescu, Rodrigo P. P. Almeida, and Steven E. Lindow. "Diffusible Signal Factor–Repressed Extracellular Traits Enable Attachment of Xylella fastidiosa to Insect Vectors and Transmission." Phytopathology® 104, no. 1 (2014): 27–33. http://dx.doi.org/10.1094/phyto-06-13-0151-r.

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The hypothesis that a wild-type strain of Xylella fastidiosa would restore the ability of rpfF mutants blocked in diffusible signal factor production to be transmitted to new grape plants by the sharpshooter vector Graphocephala atropunctata was tested. While the rpfF mutant was very poorly transmitted by vectors irrespective of whether they had also fed on plants infected with the wild-type strain, wild-type strains were not efficiently transmitted if vectors had fed on plants infected with the rpfF mutant. About 100-fewer cells of a wild-type strain attached to wings of a vector when suspended in xylem sap from plants infected with an rpfF mutant than in sap from uninfected grapes. The frequency of transmission of cells suspended in sap from plants that were infected by the rpfF mutant was also reduced over threefold. Wild-type cells suspended in a culture supernatant of an rpfF mutant also exhibited 10-fold less adherence to wings than when suspended in uninoculated culture media. A factor released into the xylem by rpfF mutants, and to a lesser extent by the wild-type strain, thus inhibits their attachment to, and thus transmission by, sharpshooter vectors and may also enable them to move more readily through host plants.

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Marucci, Rosangela Cristina, Teresinha Augusta Giustolin, Marcelo Pedreira de Miranda, Helen Miquelote, Rodrigo Piacentini Paes de Almeida, and João Roberto Spotti Lopes. "Identification of a non-host plant of Xylella fastidiosa to rear healthy sharpshooter vectors." Scientia Agricola 60, no. 4 (2003): 669–75. http://dx.doi.org/10.1590/s0103-90162003000400010.

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Rearing leafhopper (Hemiptera: Cicadellidae) vectors free of Xylella fastidiosa is a requirement for studies of various aspects of vector-pathogen interactions. The selection of a plant that allows vector development but not bacterial multiplication is desirable to produce healthy vectors. In this study, two leafhopper hosts, Vernonia condensata ('boldo') and Aloysia virgata ('lixeira') were needle inoculated with citrus and coffee strains of X. fastidiosa to evaluate if these plants support pathogen colonization. The inoculated plants did not present symptoms and the pathogen was not detected by culture and PCR tests, neither soon after inoculation (7-14 days) nor later, at 1, 4, 6 and 12 months after inoculation. To obtain healthy adults of the leafhopper vectors Acrogonia citrina, Bucephalogonia xanthophis, Dilobopterus costalimai, Homalodisca ignorata and Oncometopia facialis, early-instar nymphs were reared on V. condensata. X. fastidiosa was not detected in any of 175 adults obtained. V. condensata and A. virgata are nonpropagative hosts of X. fastidiosa and enable the production of healthy leafhoppers for vector studies.

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Esteves, Mariana B., Heloisa T. Kleina, Tiago de Melo Sales, et al. "Transmission Efficiency of Xylella fastidiosa subsp. pauca Sequence Types by Sharpshooter Vectors after In Vitro Acquisition." Phytopathology® 109, no. 2 (2019): 286–93. http://dx.doi.org/10.1094/phyto-07-18-0254-fi.

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Xylella fastidiosa subsp. pauca is genetically diverse and has many vector species. However, there is limited information on vector specificity and efficiency for different sequence types (STs) within the pathogen subspecies. Both STs of X. fastidiosa and vectors differ in their associations with plants; therefore, assessment of vector competence should include the standardized vector acquisition ability of bacteria from artificial diets. This work aimed to adapt and validate an in vitro acquisition system for strains of X. fastidiosa that cause citrus variegated chlorosis, and to compare the transmission efficiency of STs of subsp. pauca by different species of sharpshooter vector. First, acquisition and transmission of ST13 by Bucephalogonia xanthophis and Macugonalia leucomelas was tested using an artificial diet with bacteria grown on minimum defined medium (X. fastidiosa medium) with or without 1% galacturonic acid (GA). Subsequently, four sharpshooter species (B. xanthophis, M. leucomelas, M. cavifrons, and Sibovia sagata) were compared as vectors of ST13 acquired from artificial diets, and four STs of subsp. pauca (11, 13, 65, and 70) were tested for acquisition and transmission by M. leucomelas. The artificial system allowed efficient acquisition and transmission of ST13 to plants, with no differences between the media tested. ST13 was transmitted more efficiently by B. xanthophis and M. leucomelas when compared with M. cavifrons and S. sagata. Different STs influenced acquisition and transmission rates by M. leucomelas. The differences in vector competence, despite the standardized acquisition system, suggest that ST–vector foregut or vector–plant interactions may influence bacterial acquisition, retention and inoculation by the insect.

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Sisterson, Mark S., Shyamala R. Thammiraju, Kris Lynn-Patterson, Russell L. Groves, and Kent M. Daane. "Epidemiology of Diseases Caused by Xylella fastidiosa in California: Evaluation of Alfalfa as a Source of Vectors and Inocula." Plant Disease 94, no. 7 (2010): 827–34. http://dx.doi.org/10.1094/pdis-94-7-0827.

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Pierce's disease and almond leaf scorch disease have been chronic problems for California grape and almond growers, respectively. Both diseases are caused by the xylem-limited, bacterial pathogen Xylella fastidiosa, which is transmitted by xylem-feeding insects. We evaluated the potential for alfalfa to serve as a source of vectors and inocula in California. Analysis of Geographic Information Systems maps on the distribution and abundance of grape, almond, and alfalfa plantings determined that 94,521 ha of almond and grape were planted within 1.6 km of an alfalfa field. Seasonal trends of X. fastidiosa detection were monitored outdoors and in the greenhouse in five needle-inoculated alfalfa cultivars (CUF101, Moapa69, WL342, WL530HQ, and WL625HQ) over 2 years. Results suggest that cool winter temperatures reduced X. fastidiosa populations to undetectable levels but did not eliminate infections. Sampling of alfalfa fields to assess incidence of X. fastidiosa corroborated this result, with positive samples detected in summer only. Incidence of X. fastidiosa in alfalfa during summer was low, with only 6 positive samples out of 1,156 samples collected over 3 years. Insect trapping in alfalfa fields over 3 years found that the green sharpshooter (Draeculacephala minerva) was the most abundant vector. Within alfalfa fields, green sharpshooter abundance was highest in weedy areas, suggesting a preference for weeds over alfalfa. These results confirm that weedy alfalfa fields can serve as an important source of vectors. Incidence of X. fastidiosa in alfalfa was low, possibly due to preference of vectors for weeds over alfalfa.

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Bossi Esteves, Mariana, Julia Lopes Nalin, Karla Kudlawiec, et al. "XadA2 Adhesin Decreases Biofilm Formation and Transmission of Xylella fastidiosa subsp. pauca." Insects 11, no. 8 (2020): 473. http://dx.doi.org/10.3390/insects11080473.

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Xylella fastidiosa is a vector-borne bacterium that causes diseases in many plants of economic interest. The bacterium–vector initial interactions involve bacterial membrane-bound adhesins that mediate cell attachment to the foregut of insect vectors. We investigated the role of the afimbrial adhesin XadA2 in the binding and biofilm formation of X. fastidiosa subsp. pauca to vector surfaces in vitro, as well as its potential to disrupt pathogen transmission. We showed that XadA2 has binding affinity for polysaccharides on sharpshooter hindwings, used as a proxy for the interactions between X. fastidiosa and vectors. When in a medium without carbon sources, the bacterium used wing components, likely chitin, as a source of nutrients and formed a biofilm on the wing surface. There was a significant reduction in X. fastidiosa biofilm formation and cell aggregation on vector wings in competition assays with XadA2 or its specific antibody (anti-XadA2). Finally, pathogen acquisition and transmission to plant were significantly reduced when the vectors acquired X. fastidiosa from an artificial diet supplemented with anti-XadA2. These results show that XadA2 is important in mediating bacterial colonization in the insect and that it could be used as a target for blocking X. fastidiosa transmission.

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Myers, Ashley L., Turner B. Sutton, Jorge A. Abad, and George G. Kennedy. "Pierce's Disease of Grapevines: Identification of the Primary Vectors in North Carolina." Phytopathology® 97, no. 11 (2007): 1440–50. http://dx.doi.org/10.1094/phyto-97-11-1440.

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In the past 10 years, the winegrape industry in the southeastern United States has experienced rapid growth; however, further expansion may be inhibited by Pierce's disease (PD). Epidemiological studies were conducted to identify the primary vectors of Xylella fastidiosa, the cause of PD of grape, by surveying sharpshooter population dynamics in the eastern Piedmont and Coastal Plain regions of North Carolina. Sharpshooter species were assessed for the presence of X. fastidiosa in the field. Leafhoppers were trapped in three vineyards in the eastern Piedmont and one vineyard in the northeastern Coastal Plain in 2004 and 2005. Four insects were identified as most abundant: Oncometopia orbona, Graphocephala versuta, Paraphlepsius irroratus, and Agalliota constricta. Adult specimens of O. orbona, G. versuta, and P. irroratus were tested for the presence of X. fastidiosa by nested polymerase chain reaction. In all, 27% of O. orbona, 28% of G. versuta, and 33% of P. irroratus trapped were positive for X. fastidiosa over the two seasons. Transmission experiments demonstrated that both O. orbona and G. versuta have the ability to transmit X. fastidiosa to grape. These vectors are likely to be important in all winegrowing regions of the Southeast, because their presence has been documented throughout the southern states. In DNA analyses, X. fastidiosa strains from insects trapped in North Carolina were genetically similar to one another and to the known “PD strain” from California. This is the first report of these two leafhopper species transmitting X. fastidiosa to grapevines in the Southeast.

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Hill, B. L., and A. H. Purcell. "Populations of Xylella fastidiosa in Plants Required for Transmission by an Efficient Vector." Phytopathology® 87, no. 12 (1997): 1197–201. http://dx.doi.org/10.1094/phyto.1997.87.12.1197.

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Xylella fastidiosa, a xylem-limited bacterium that causes Pierce's disease (PD) of grapevine and other diseases, is transmitted efficiently by xylem-feeding leafhoppers. Acquisition of a PD strain of X. fastidiosa by the blue-green sharpshooter (BGSS) from five plant host species—grapevine (Vitis vinifera), Himalayan blackberry (Rubus discolor), California mugwort (Artemisia douglasiana), watergrass (Echinochloa crus-galli), and Bermuda grass (Cynodon dactylon)—was tested at various time intervals after vector inoculation. The minimum incubation periods in plant hosts before BGSS acquired X. fastidiosa were 4, 22, 29, and 25 days for grapevine, blackberry, mugwort, and watergrass, respectively. There were no transmissions by vectors or recoveries of X. fastidiosa by culturing from Bermuda grass in 133 attempts, including 80 attempts with the green sharpshooter, Draeculacephala minerva. The first acquisitions and subsequent transmissions by BGSS occurred after X. fastidiosa multiplied to a population of about 104 CFU/g of stem tissue. Higher populations of bacteria in plants resulted in higher rates of transmission. In grapevine, the rate of transmission increased over time (4.5% in the first 10 days to 55% after day 25) as the maximum number of viable CFU of X. fas-tidiosa recovered by culturing also increased (from 5 × 105 CFU/g during the first 10 days to 5 × 108 after day 25).

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Rapicavoli, Jeannette N., Nichola Kinsinger, Thomas M. Perring, et al. "O Antigen Modulates Insect Vector Acquisition of the Bacterial Plant Pathogen Xylella fastidiosa." Applied and Environmental Microbiology 81, no. 23 (2015): 8145–54. http://dx.doi.org/10.1128/aem.02383-15.

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ABSTRACTHemipteran insect vectors transmit the majority of plant pathogens. Acquisition of pathogenic bacteria by these piercing/sucking insects requires intimate associations between the bacterial cells and insect surfaces. Lipopolysaccharide (LPS) is the predominant macromolecule displayed on the cell surface of Gram-negative bacteria and thus mediates bacterial interactions with the environment and potential hosts. We hypothesized that bacterial cell surface properties mediated by LPS would be important in modulating vector-pathogen interactions required for acquisition of the bacterial plant pathogenXylella fastidiosa, the causative agent of Pierce's disease of grapevines. Utilizing a mutant that produces truncated O antigen (the terminal portion of the LPS molecule), we present results that link this LPS structural alteration to a significant decrease in the attachment ofX. fastidiosato blue-green sharpshooter foreguts. Scanning electron microscopy confirmed that this defect in initial attachment compromised subsequent biofilm formation within vector foreguts, thus impairing pathogen acquisition. We also establish a relationship between O antigen truncation and significant changes in the physiochemical properties of the cell, which in turn affect the dynamics ofX. fastidiosaadhesion to the vector foregut. Lastly, we couple measurements of the physiochemical properties of the cell with hydrodynamic fluid shear rates to produce a Comsol model that predicts primary areas of bacterial colonization within blue-green sharpshooter foreguts, and we present experimental data that support the model. These results demonstrate that, in addition to reported protein adhesin-ligand interactions, O antigen is crucial for vector-pathogen interactions, specifically in the acquisition of this destructive agricultural pathogen.

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Farias, Paulo R. S., Sérgio R. Roberto, João R. S. Lopes, and Dilermando Perecin. "Geostatistical characterization of the spatial distribution of Xylella fastidiosa sharpshooter vectors on citrus." Neotropical Entomology 33, no. 1 (2004): 13–20. http://dx.doi.org/10.1590/s1519-566x2004000100004.

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Stenger, Drake C., Lindsey P. Burbank, Rodrigo Krugner, and Mark S. Sisterson. "Individual field-collected glassy-winged sharpshooter vectors harbor sequences from two Xylella fastidiosa subspecies." European Journal of Plant Pathology 155, no. 1 (2019): 329–38. http://dx.doi.org/10.1007/s10658-019-01742-x.

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Daugherty, Matthew P., and Rodrigo P. P. Almeida. "Understanding How an Invasive Vector Drives Pierce’s Disease Epidemics: Seasonality and Vine-to-Vine Spread." Phytopathology® 109, no. 2 (2019): 277–85. http://dx.doi.org/10.1094/phyto-07-18-0217-fi.

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For vector-borne plant pathogens, disease epidemics may be attributable to multiple mechanisms, including introduction of a novel vector whose epidemiological role differs from that of native vectors. In such cases, understanding an exotic vector’s ability to drive an epidemic is central to mitigating its impact. We studied how the invasive glassy-winged sharpshooter (Homalodisca vitripennis Germar) can drive Pierce’s disease outbreaks in vineyards, focusing on its potential to promote vine-to-vine (i.e., secondary) spread of Xylella fastidiosa relative to potential constraints stemming from seasonality in the pathosystem. First, we developed a general vector-borne disease model to understand the consequences for disease dynamics of (i) seasonal acquisition efficiency and (ii) seasonal host recovery from infection. Results of the modeling indicate that these two sources of seasonality could constrain disease incidence, particularly when working in concert. Next, we established a field cage experiment to determine whether H. vitripennis promotes vine-to-vine spread, and looked for evidence of seasonality in spread. Broadly, results from the experiment supported assumptions of the model; there was modest to significant increase in the frequency of pathogen spread over the first season, and those new infections that occurred later in the season were more likely to recover during winter. Ultimately, by the end of the second season, there was not evidence of significant secondary spread, likely due to a combination of seasonal constraints and low transmission efficiency by H. vitripennis. Collectively, these results suggest that, although H. vitripennis may be able to promote vine-to-vine spread in certain contexts, it may not be the key factor explaining its impact. Rather, the ability of H. vitripennis to drive epidemics is likely to be more directly related to its potential to reach higher population densities than native vectors.

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Sisterson, Mark S., Lindsey P. Burbank, Rodrigo Krugner, David Haviland, and Drake C. Stenger. "Xylella fastidiosa and Glassy-Winged Sharpshooter Population Dynamics in the Southern San Joaquin Valley of California." Plant Disease 104, no. 11 (2020): 2994–3001. http://dx.doi.org/10.1094/pdis-01-20-0066-re.

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Xylella fastidiosa is a vector-transmitted bacterial plant pathogen that affects a wide array of perennial crops, including grapevines (Pierce’s disease). In the southern San Joaquin Valley of California, epidemics of Pierce’s disease of grapevine were associated with the glassy-winged sharpshooter, Homalodisca vitripennis. During the growing season, rates of X. fastidiosa spread in vineyards are affected by changes in pathogen distribution within chronically infected grapevines and by vector population dynamics. Grapevines chronically infected with X. fastidiosa rarely tested positive for the pathogen prior to July, suggesting vector acquisition of X. fastidiosa from grapevines increases as the season progresses. This hypothesis was supported by an increase in number of X. fastidiosa-positive glassy-winged sharpshooters collected from vineyards during July through September. Analysis of insecticide records indicated that vineyards in the study area were typically treated with a systemic neonicotinoid in spring of each year. As a result, abundance of glassy-winged sharpshooters was typically low in late spring and early summer, with abundance of glassy-winged sharpshooter adults increasing in late June and early July of each year. Collectively, the results suggest that late summer is a crucial time for X. fastidiosa secondary spread in vineyards in the southern San Joaquin Valley, because glassy-winged sharpshooter abundance, number of glassy-winged sharpshooters testing positive for X. fastidiosa, and grapevines with detectable pathogen populations were all greatest during this period.

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Tubajika, K. M., E. L. Civerolo, M. A. Ciomperlik, D. A. Luvisi, and J. M. Hashim. "Analysis of the Spatial Patterns of Pierce's Disease Incidence in the Lower San Joaquin Valley in California." Phytopathology® 94, no. 10 (2004): 1136–44. http://dx.doi.org/10.1094/phyto.2004.94.10.1136.

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The incidence of Pierce's disease (PD), caused by Xylella fastidiosa, was monitored in 11 naturally infested commercial vineyards to determine the presence of an X. fastidiosa vector, Homalodisca coagulata (glassy-winged sharpshooter [GWSS]), to examine the spatial patterns of the disease and elucidate possible influences of surrounding environments. Disease incidence ranged from <1 to 65% among vineyards in 2001. Our efforts to trap or capture potential disease vectors have indicated that the GWSS is the most likely vector. Disease incidence doubled in most vineyards during the 2002 production season. Spatial patterns of symptomatic vines in 2001 and 2002, as determined by ordinary runs analysis, showed strong evidence for within- and across-row aggregation of infected vines. In most fields, they were no disease gradients observed relative to GWSS source (e.g., citrus). Within fields, however, disease incidence displayed strong spatial dependence and a high degree of anisotropy, indicating strongly aggregated patterns of disease with distinct directional orientation. The within-row (0°) and across-row (90°) orientations generally were the predominant directions of increased disease incidence, consistent with vine-to-vine spread of X. fastidiosa. We concluded that the distribution of PD in vineyards reflected the feeding pattern of vectors carrying X. fastidiosa. Based on these results, effective PD management is likely to be based on practices that reduce significant insect vector populations and remove infected vines as soon as identified and on the use of resistant cultivars.

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Lessio, Federico, and Alberto Alma. "Models Applied to Grapevine Pests: A Review." Insects 12, no. 2 (2021): 169. http://dx.doi.org/10.3390/insects12020169.

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This paper reviews the existing predictive models concerning insects and mites harmful to grapevine. A brief conceptual description is given on the definition of a model and about different types of models: deterministic vs. stochastics, continuous vs. discrete, analytical vs. computer-based, and descriptive vs. data-driven. The main biological aspects of grapevine pests covered by different types of models are phenology, population growth and dynamics, species distribution, and invasion risk. A particular emphasis is put on forecasting epidemics of plant disease agents transmitted by insects with sucking-piercing mouthparts. The most investigated species or groups are the glassy-winged sharpshooter Homalodisca vitripennis (Germar) and other vectors of Xylella fastidiosa subsp. fastidiosa, a bacterium agent of Pierce’s disease; the European grape berry moth, Lobesia botrana (Denis and Schiffermuller); and the leafhopper Scaphoideus titanus Ball, the main vector of phytoplasmas agents of Flavescence dorée. Finally, the present and future of decision-support systems (DSS) in viticulture is discussed.

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Alves, Eduardo, Breno Leite, Rosangela C. Marucci, Sérgio F. Pascholati, João R. S. Lopes, and Peter C. Andersen. "Retention Sites for Xylella fastidiosa in Four Sharpshooter Vectors (Hemiptera: Cicadellidae) Analyzed by Scanning Electron Microscopy." Current Microbiology 56, no. 5 (2008): 531–38. http://dx.doi.org/10.1007/s00284-008-9119-7.

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Almeida, Rodrigo P. P., and Alexander H. Purcell. "Patterns of Xylella fastidiosa Colonization on the Precibarium of Sharpshooter Vectors Relative to Transmission to Plants." Annals of the Entomological Society of America 99, no. 5 (2006): 884–90. http://dx.doi.org/10.1603/0013-8746(2006)99[884:poxfco]2.0.co;2.

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Kleina, Heloisa Thomazi, Karla Kudlawiec, Mariana B. Esteves, et al. "Settling and feeding behavior of sharpshooter vectors of Xylella fastidiosa on plum genotypes resistant to leaf scald disease." European Journal of Plant Pathology 158, no. 3 (2020): 633–44. http://dx.doi.org/10.1007/s10658-020-02104-8.

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Ringenberg, Rudiney, João Roberto Spotti Lopes, Cristiane Müller, Wilson Sampaio de Azevedo-Filho, Beatriz Aguiar Jordão Paranhos, and Marcos Botton. "Survey of potential sharpshooter and spittlebug vectors of Xylella fastidiosa to grapevines at the São Francisco River Valley, Brazil." Revista Brasileira de Entomologia 58, no. 2 (2014): 212–18. http://dx.doi.org/10.1590/s0085-56262014000200013.

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Lopes, Silvio A., Laudecir L. Raiol-Júnior, Simone C. Z. Torres, Elaine C. Martins, Simone S. Prado, and Luís O. S. Beriam. "Differential Responses of Tobacco to the Citrus Variegated Chlorosis and Coffee Stem Atrophy Strains of Xylella fastidiosa." Phytopathology® 110, no. 3 (2020): 567–73. http://dx.doi.org/10.1094/phyto-10-19-0374-r.

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Xylella fastidiosa comprises a diverse group of xylem-limited, insect-transmitted bacterial pathogens. In Brazil, the citrus variegated chlorosis (CVC) and coffee stem atrophy (CSA) diseases are caused by X. fastidiosa subspecies pauca transmitted by common insect vectors. No simple protocol allowing strain discrimination exists, making epidemiological studies, which are important for devising control measures, difficult to undertake. Here, we show that both strains can easily be distinguished based on the pattern of leaf symptoms that they induce on pin prick-inoculated tobacco seedlings, namely small orange lesions and large necrotic lesions induced by the CVC and CSA strains, respectively. These differential responses allowed us to investigate whether mixed strain infections would occur in citrus or coffee trees in the field. Seedlings were individually inoculated with X. fastidiosa colonies recovered from citrus or coffee plants from various locations at three different times. No mixed infections were detected. In two experiments, the citrus and coffee strains infected only their original hosts as well as tobacco. The usefulness of this tobacco bioassay as a tool to study X. fastidiosa spread was demonstrated. It provided evidence that, over the years, the CVC and CSA pathogens have remained limited to their original hosts, despite crop proximity and the presence of sharpshooter vectors that favor transmission of the bacteria to and between both host species.

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Wang, Nian, Jian-Liang Li, and Steven E. Lindow. "RpfF-Dependent Regulon of Xylella fastidiosa." Phytopathology® 102, no. 11 (2012): 1045–53. http://dx.doi.org/10.1094/phyto-07-12-0146-r.

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Xylella fastidiosa regulates traits important to both virulence of grape as well as colonization of sharpshooter vectors via its production of a fatty acid signal molecule known as DSF whose production is dependent on rpfF. Although X. fastidiosa rpfF mutants exhibit increased virulence to plants, they are unable to be spread from plant to plant by insect vectors. To gain more insight into the traits that contribute to these processes, a whole-genome Agilent DNA microarray for this species was developed and used to determine the RpfF-dependent regulon by transcriptional profiling. In total, 446 protein coding genes whose expression was significantly different between the wild type and an rpfF mutant (false discovery rate < 0.05) were identified when cells were grown in PW liquid medium. Among them, 165 genes were downregulated in the rpfF mutant compared with the wild-type strain whereas 281 genes were over-expressed. RpfF function was required for regulation of 11 regulatory and σ factors, including rpfE, yybA, PD1177, glnB, rpfG, PD0954, PD0199, PD2050, colR, rpoH, and rpoD. In general, RpfF is required for regulation of genes involved in attachment and biofilm formation, enhancing expression of hemagglutinin genes hxfA and hxfB, and suppressing most type IV pili and gum genes. A large number of other RpfF-dependent genes that might contribute to virulence or insect colonization were also identified such as those encoding hemolysin and colicin V, as well as genes with unknown functions.

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Costa, H. S., M. S. Blua, J. A. Bethke, and R. A. Redak. "Transmission of Xylella fastidiosa to Oleander by the Glassywinged Sharpshooter, Homalodisca coagulata." HortScience 35, no. 7 (2000): 1265–67. http://dx.doi.org/10.21273/hortsci.35.7.1265.

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Studies were conducted to investigate the transmission of the oleander leaf scorch (OLS) pathogen to oleander (Nerium oleander L.) plants by sharpshooters. OLS is incited by a strain of the bacterial plant pathogen Xylella fastidiosa Well. The glassywinged sharpshooter, Homalodisca coagulata (Say), is a principal vector of this pathogen in California. In these studies, three cultivars of oleander were exposed to sharpshooters that had previously fed upon OLS-infected oleander plants. Sharpshooters were subsequently caged on healthy oleander plants individually or in groups of three. Plants were observed for symptoms of disease, and ELISA was used to test for the presence of X. fastidiosa. The probability of infection did not differ significantly when plants were inoculated with one insect (83%) or with three (94%). However, higher plant mortality rates were observed on plants inoculated with three insects, indicating that a greater number of infection sites may hasten plant death. Although all oleander cultivars were equally susceptible to inoculation by sharpshooters, `Ruby Lace' plants were less symptomatic and had a higher level of survival after one year than `Hardy Pink' and `Hardy Red'. When given a choice of the three cultivars to feed on, the number of insects feeding did not differ among cultivars at 24 or 48 hours after exposure.

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Sengoda, Venkatesan G., Xiangyang Shi, Rodrigo Krugner, Elaine A. Backus, and Hong Lin. "Targeted Mutations in Xylella fastidiosa Affect Acquisition and Retention by the Glassy-Winged Sharpshooter, Homalodisca vitripennis (Hemiptera: Cicadellidae)." Journal of Economic Entomology 113, no. 2 (2020): 612–21. http://dx.doi.org/10.1093/jee/toz352.

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Abstract Xylella fastidiosa (Wells) is a xylem-limited bacterium that causes Pierce’s disease of grapevines. The bacterium is transmitted by insect vectors such as the glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar). Experiments were conducted to compare the role of selected X. fastidiosa genes on 1) bacterial acquisition and retention in GWSS foreguts, and 2) transmission to grapevines by GWSS. Bacterial genotypes used were: mutants Xf-ΔpilG, Xf-ΔpilH, Xf-ΔgacA, and Xf-ΔpopP; plus wild type (WT) as control. Results showed that Xf-ΔpilG had enhanced colonization rate and larger numbers in GWSS compared with WT. Yet, Xf-ΔpilG exhibited the same transmission efficiency as WT. The Xf-ΔpilH exhibited poor acquisition and retention. Although initial adhesion, multiplication, and retention of Xf-ΔpilH in GWSS were almost eliminated compared with WT, the mutation did not reduce transmission success in grapevines. Overall, Xf-ΔgacA showed colonization rates and numbers in foreguts similar to WT. The Xf-ΔgacA mutation did not affect initial adhesion, multiplication, and long-term retention compared with WT, and was not significantly diminished in transmission efficiency. In contrast, numbers of Xf-ΔpopP were variable over time, displaying greatest fluctuation from highest to lowest levels. Thus, Xf-ΔpopP had a strong, negative effect on initial adhesion, but adhered and slowly multiplied in the foregut. Again, transmission was not diminished compared to WT. Despite reductions in acquisition and retention by GWSS, transmission efficiency of genotypes to grapevines was not affected. Therefore, in order to stop the spread of X. fastidiosa by GWSS using gene-level targets, complete disruption of bacterial colonization mechanisms is required.

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Lindow, Steven, Karyn Newman, Subhadeep Chatterjee, Clelia Baccari, Anthony T. Iavarone, and Michael Ionescu. "Production of Xylella fastidiosa Diffusible Signal Factor in Transgenic Grape Causes Pathogen Confusion and Reduction in Severity of Pierce's Disease." Molecular Plant-Microbe Interactions® 27, no. 3 (2014): 244–54. http://dx.doi.org/10.1094/mpmi-07-13-0197-fi.

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The rpfF gene from Xylella fastidiosa, encoding the synthase for diffusible signal factor (DSF), was expressed in ‘Freedom’ grape to reduce the pathogen's growth and mobility within the plant. Symptoms in such plants were restricted to near the point of inoculation and incidence of disease was two- to fivefold lower than in the parental line. Both the longitudinal and lateral movement of X. fastidiosa in the xylem was also much lower. DSF was detected in both leaves and xylem sap of RpfF-expressing plants using biological sensors, and both 2-Z-tetradecenoic acid, previously identified as a component of X. fastidiosa DSF, and cis-11-methyl-2-dodecenoic acid were detected in xylem sap using electrospray ionization mass spectrometry. A higher proportion of X. fastidiosa cells adhered to xylem vessels of the RpfF-expressing line than parental ‘Freedom’ plants, reflecting a higher adhesiveness of the pathogen in the presence of DSF. Disease incidence in RpfF-expressing plants in field trials in which plants were either mechanically inoculated with X. fastidiosa or subjected to natural inoculation by sharpshooter vectors was two- to fourfold lower in than that of the parental line. The number of symptomatic leaves on infected shoots was reduced proportionally more than the incidence of infection, reflecting a decreased ability of X. fastidiosa to move within DSF-producing plants.

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Li, W. B., W. D. Pria, D. C. Teixeira, et al. "Coffee Leaf Scorch Caused by a Strain of Xylella fastidiosa from Citrus." Plant Disease 85, no. 5 (2001): 501–5. http://dx.doi.org/10.1094/pdis.2001.85.5.501.

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Citrus variegated chlorosis (CVC) and coffee leaf scorch (CLS) are two economically important diseases in Brazil caused by the bacterium Xylella fastidiosa. Strains of the bacterium isolated from the two plant hosts are very closely related, and the two diseases share sharpshooter insect vectors. In order to determine if citrus strains of X. fastidiosa could infect coffee and induce CLS disease, plant inoculations were performed. Plants of coffee, Coffea arabica ‘Mundo Novo’, grafted on Coffea canephora var. robusta ‘Apuatão 2258’ were mechanically inoculated with triply cloned strains of X. fastidiosa isolated from diseased coffee and citrus. Three months postinoculation, 5 of the 10 plants inoculated with CLS-X. fastidiosa and 1 of the 10 plants inoculated with CVC-X. fastidiosa gave positive enzyme-linked immunosorbent assay (ELISA) and/or polymerase chain reaction (PCR). Eight months postinoculation, another six plants inoculated with CVC-X. fastidiosa gave positive PCR results. The two X. fastidiosa strains were isolated from the inoculated plants and showed the same characteristics as the original clones by microscopy, ELISA, and PCR. None of the plants inoculated with sterile periwinkle wilt (PW) medium as controls gave positive reactions in diagnostic tests, and none developed disease symptoms. Six months postinoculation, seven plants inoculated with CLS-X. fastidiosa and eight inoculated with CVC-X. fastidiosa began to develop characteristic CLS symptoms, including apical and marginal leaf scorch, defoliation, and reductions of internode length, leaf size, and plant height, terminal clusters of small chlorotic and deformed leaves, and lateral shoot dieback. We have demonstrated that X. fastidiosa from citrus plants is pathogenic for coffee plants. This has important consequences for the management of CLS disease and has implications for the origin of citrus variegated chlorosis disease.

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Puterka, Gary J., Mike Reinke, Donald Luvisi, Matthew A. Ciomperik, David Bartels, and D. Michael Glenn. "Particle Film, Surround WP, Effects on Glassy-winged Sharpshooter Behavior and Its Utility as a Barrier to Sharpshooter Infestations in Grape." Plant Health Progress 4, no. 1 (2003): 7. http://dx.doi.org/10.1094/php-2003-0321-01-rs.

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Glassy-winged sharpshooter (GWSS) was recently introduced into California and poses a serious threat to the grape industry because it is a very effective vector of the bacterium that causes Pierce's disease. We studied how GWSS was affected by a new technology called particle film, Surround™ WP, that protects plants from insect feeding, oviposition, and infestation by coating the plant surfaces with a protective mineral barrier. In caged field studies, we found that GWSS nymphs and adults were highly repelled by lemon trees treated with Surround WP. Applications of Surround WP turn foliage white; thus, we compared the attractiveness of white and other colors with yellow, which is extremely attractive to GWSS. This study showed that yellow was the most attractive color, followed by orange, and that white was among the least attractive colors, suggesting that Surround WP applications may make plants unrecognizable as hosts. In a field study that compared three biweekly Surround WP treatments to six weekly contact insecticide treatments, Surround WP performed as well as insecticides in reducing GWSS adult numbers and oviposition. Accepted for publication 25 February 2003. Published 21 March 2003.

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Molina, Rúbia de Oliveira, Aline Maria Orbolato Gonçalves, Carlos Alexandre Zanutto, and William Mário de Carvalho Nunes. "Populational fluctuation of vectors of Xylella fastidiosa, wells in sweet orange [Citrus sinensis (L.) Osbeck] varieties of northwest Paraná State, Brazil." Brazilian Archives of Biology and Technology 53, no. 3 (2010): 549–54. http://dx.doi.org/10.1590/s1516-89132010000300007.

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The aim of the present study was to assess the population flutuation of the sharpshooters species subfamily Cicadellinae belonging to the tribes Cicadellini and Proconiini, in sweet orange [Citrus sinensis( L). Osbeck] commercial orchards of the northwest region of Paraná State , Brazil. Samplings were carried out the employing every time 24 yellow sticky cards. Identification of the species showed that the most representative were Dilobopterus costalimai of the Cicadellini tribe and Acrogonia citrina of the Proconiini tribe.

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Bhowmick, Tushar Suvra, Mayukh Das, Kevin M. Heinz, Peter C. Krauter, and Carlos F. Gonzalez. "Transmission of phage by glassy-winged sharpshooters, a vector ofXylella fastidiosa." Bacteriophage 6, no. 3 (2016): e1218411. http://dx.doi.org/10.1080/21597081.2016.1218411.

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Almeida, R. P. P., C. Wistrom, B. L. Hill, J. Hashim, and A. H. Purcell. "Vector Transmission of Xylella fastidiosa to Dormant Grape." Plant Disease 89, no. 4 (2005): 419–24. http://dx.doi.org/10.1094/pd-89-0419.

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Homalodisca coagulata (Say) is a sharpshooter leafhopper vector of the bacterial plant pathogen Xylella fastidiosa. Introduced into California about 15 years ago, this insect triggered recent outbreaks of Pierce's disease of grapevine in the state. H. coagulata has been observed feeding on dormant grapevines during the winter, raising the possibility of X. fastidiosa transmission during that season. We tested whether H. coagulata can acquire X. fastidiosa from and inoculate the bacterium to dormant grape (Vitis vinifera) in the laboratory and in the field. Usually, >90% of H. coagulata survived on dormant plants in the laboratory and field. Field experiments showed that H. coagulata can inoculate X. fastidiosa into dormant plants, yet field acquisition experiments did not result in transmission. Transmission to dormant plants during the winter is a potential problem in California vineyards adjacent to citrus groves or other habitats with large overwintering populations of H. coagulata. Because dormant plants have positive root pressure, our findings provide evidence that X. fastidiosa transmission does not require negative pressure in plant xylem to be inoculated into plants.

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Backus, Elaine A., Holly J. Shugart, Elizabeth E. Rogers, J. Kent Morgan, and Robert Shatters. "Direct Evidence of Egestion and Salivation of Xylella fastidiosa Suggests Sharpshooters Can Be “Flying Syringes”." Phytopathology® 105, no. 5 (2015): 608–20. http://dx.doi.org/10.1094/phyto-09-14-0258-r.

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Xylella fastidiosa is unique among insect-transmitted plant pathogens because it is propagative but noncirculative, adhering to and multiplying on the cuticular lining of the anterior foregut. Any inoculation mechanism for X. fastidiosa must explain how bacterial cells exit the vector’s stylets via the food canal and directly enter the plant. A combined egestion-salivation mechanism has been proposed to explain these unique features. Egestion is the putative outward flow of fluid from the foregut via hypothesized bidirectional pumping of the cibarium. The present study traced green fluorescent protein-expressing X. fastidiosa or fluorescent nanoparticles acquired from artificial diets by glassy-winged sharpshooters, Homalodisca vitripennis, as they were egested into simultaneously secreted saliva. X. fastidiosa or nanoparticles were shown to mix with gelling saliva to form fluorescent deposits and salivary sheaths on artificial diets, providing the first direct, conclusive evidence of egestion by any hemipteran insect. Therefore, the present results strongly support an egestion-salivation mechanism of X. fastidiosa inoculation. Results also support that a column of fluid is transiently held in the foregut without being swallowed. Evidence also supports (but does not definitively prove) that bacteria were suspended in the column of fluid during the vector’s transit from diet to diet, and were egested with the held fluid. Thus, we hypothesize that sharpshooters could be true “flying syringes,” especially when inoculation occurs very soon after uptake of bacteria, suggesting the new paradigm of a nonpersistent X. fastidiosa transmission mechanism.

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DAUGHERTY, MATTHEW P., ARASH RASHED, RODRIGO P. P. ALMEIDA, and THOMAS M. PERRING. "Vector preference for hosts differing in infection status: sharpshooter movement and Xylella fastidiosa transmission." Ecological Entomology 36, no. 5 (2011): 654–62. http://dx.doi.org/10.1111/j.1365-2311.2011.01309.x.

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Backus, Elaine A., Kim B. Andrews, Holly J. Shugart, L. Carl Greve, John M. Labavitch, and Hasan Alhaddad. "Salivary enzymes are injected into xylem by the glassy-winged sharpshooter, a vector of Xylella fastidiosa." Journal of Insect Physiology 58, no. 7 (2012): 949–59. http://dx.doi.org/10.1016/j.jinsphys.2012.04.011.

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Visnovsky, Sandra B., Robert K. Taylor, and David A. J. Teulon. "Current and planned research for managing the risk of Xylella fastidiosa to New Zealand." New Zealand Plant Protection 72 (July 28, 2019): 284. http://dx.doi.org/10.30843/nzpp.2019.72.320.

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Xylella fastidiosa (Xf), a xylem-limited bacterium native to the Americas, has a devastating impact on many crops internationally. In California, Xf causes over USD 100 million in yearly losses to the grape industry and infects an estimated 200 million citrus trees in Brazil. More recently, Xf killed around one million olive trees on the Italian peninsula of Salento. Xylella fastidiosa is not known to be present in New Zealand. The glassy-winged sharpshooter (Homalodisca vitripennis), an important vector of Xf in California, is also not present in New Zealand. However, the meadow spittle bug (Philaenus spumarius), an important vector of Xf in Italy, is present. Many economically important horticultural, viticultural, agricultural, amenity and indigenous/native plant species, including taonga, are likely to be susceptible to Xf. Aspects of our research on Xf to understand the impact, reduce the likelihood of entry into New Zealand and/or minimising its impact in New Zealand will be presented. The research listed on the poster spans risk assessment, diagnostics, surveillance and biological control but could certainly be increased across the biosecurity continuum given the magnitude of the threat from Xf to New Zealand’s valuable plant systems.

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Dara, Surendra K., Michael R. McGuire, Mauricio Ulloa, and Harry K. Kaya. "Evaluation and Molecular Characterization of Beauveria bassiana for the Control of the Glassy-winged Sharpshooter (Homoptera: Cicadellidae) in California." Journal of Entomological Science 43, no. 2 (2008): 241–46. http://dx.doi.org/10.18474/0749-8004-43.2.241.

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The glassy-winged sharpshooter, Homalodisca coagulata (Say), is an important pest on grapes, citrus, almonds and other commercial crops in California as it is a vector of Xylella fastidiosa Wells, a bacterium that causes Pierce's disease in grapes, citrus variegated chlorosis, almond leaf scorch and other plant diseases. Various entomopathogenic fungi isolated from natural infections of H. coagulata, its habitats and other insect hosts were evaluated against this insect vector. Based on these studies, 3 isolates of the hyphomycetous fungus, Beauveria bassiana (Balsamo) Vuillemin, were selected for further evaluation. Two of these were California isolates, one each from the three-cornered alfalfa hopper, Spissistilus festinus (Say), and soil from H. coagulata habitat, and the third was a Texas isolate from natural infections of H. coagulata. All three were similar in their virulence to H. coagulata under laboratory conditions. The genetic relatedness of the B. bassiana isolates also was compared using single sequence repeat (SSR) markers which showed genetic diversity of this species based on the source of the isolate. Some isolates were 4× more infectious than others demonstrating that virulence of B. bassiana is not necessarily associated with their genetic relatedness.

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Andersen, Peter C., Russell F. Mizell, Brent V. Brodbeck, Thomas G. Beckman, and Gerard Krewer. "Abundance and Consumption Rate of Glassy-Winged Sharpshooter (Hemiptera: Cicadellidae) on Peaches and Plums." Journal of Entomological Science 43, no. 4 (2008): 394–407. http://dx.doi.org/10.18474/0749-8004-43.4.394.

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Homalodisca vitripennis (Germar), the glassy-winged sharpshooter, is a primary vector of phony peach and plum leaf scald diseases caused by Xylella fastidiosa Wells et al. A survey of H. vitripennis on peach [Prunus persica (L.) Batsch] varieties established that leafhopper abundances varied from 0–13 per tree. Prunus persica cvs. Flordaking and June Gold and Prunus salicina Lindl. (cvs. Methley and Santa Rosa) were then budded on each of 3 P. persica rootstocks (cvs. Aldrighi, Lovell and Nemaguard). Leafhopper abundance was monitored on each of the two scions budded on each rootstock and on non budded rootstocks over a 2-yr period. The genotypes were container-grown in Year 1 and were planted in the field in Year 2. For both years leafhopper abundance was greatest during early June and on Methley and Santa Rosa cultivars compared with the peach genotypes. The feeding rates of leafhoppers were substantially higher on plum scions than on peach scions, and nocturnal feeding rates were often higher than daytime feeding rates. Mean leafhopper feeding rates were correlated with leafhopper abundance on Prunus genotypes from 3–8 June in a quadratic manner (F = 53.8; df = 2,12; R2 = 0.90; P &lt; 0.0001); the mean nighttime feeding rate was best correlated linearly to mean cumulative leafhopper abundance (F= 446.9; df = 1,13; R2 = 0.972; P &lt; 0.0001).

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Almeida, R. P. P., and A. H. Purcell. "Homalodisca coagulata (Hemiptera, Cicadellidae) Transmission of Xylella fastidiosa to Almond." Plant Disease 87, no. 10 (2003): 1255–59. http://dx.doi.org/10.1094/pdis.2003.87.10.1255.

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Almond leaf scorch (ALS) is caused by the bacterium Xylella fastidiosa, transmitted by sharpshooter leafhoppers and spittlebugs. The recent invasion of a X. fastidiosa vector, Homalodisca coagulata (Hemiptera, Cicadellidae), into California may have major consequences to the spread of ALS because this insect feeds readily on trees, including stone fruit species. We found that, under laboratory conditions, H. coagulata acquired X. fastidiosa from symptomatic almond plants with low efficiency relative to grape (3.3 to 10% per individual per day). Inoculation efficiency also was low, approximately 4% per insect per day. H. coagulata inoculated 1-year-old woody tissues of almond plants at similar rates as green shoots. H. coagulata transmitted two X. fastidiosa grape strains from grape source plants to grape and almond. We also observed X. fastidiosa transmission to dormant almond plants. X. fastidiosa populations in the petioles of field-collected symptomatic almond leaves were not higher than 107 CFU/g of tissue, suggesting that low bacterial populations within almond are partially responsible for the lower acquisition rates observed from diseased almond compared with diseased grape, which are usually within the range of 108 to 109 CFU/g. The relevance of our findings to ALS epidemiology, considering H. coagulata as a vector, is discussed.

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Tertuliano, M., R. Srinivasan, and H. Scherm. "Settling behavior of the glassy-winged sharpshooter, Homalodisca vitripennis, vector of Xylella fastidiosa, on southern highbush blueberry cultivars." Entomologia Experimentalis et Applicata 143, no. 1 (2012): 67–73. http://dx.doi.org/10.1111/j.1570-7458.2012.01228.x.

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Azevedo, Ruberval Leone, and Marcel Faria Lima. "Cigarrinhas dos Citros, Vetoras da Bactéria Xylella fastidiosa Wells et al.: Pragas Potenciais para a Citricultura Sergipana." EntomoBrasilis 8, no. 1 (2015): 01–07. http://dx.doi.org/10.12741/ebrasilis.v8i1.403.

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A citricultura no Brasil exerce um papel de grande importância econômica, social, gerando empregos, renda e desenvolvimento. O Brasil é o maior produtor mundial de citros, o Estado de Sergipe destaca-se em 5º lugar nacional em produção. Dentre os vários problemas fitossanitários enfrentados pela citricultura brasileira está a Clorose Variegada dos Citros (CVC), conhecida como amarelinho, causada pela bactéria Xylella fastidiosa Wells et al. A CVC foi identificada oficialmente no Brasil, em 1987, em pomares do Triângulo Mineiro e do Norte e Noroeste do Estado de São Paulo. No Nordeste, foi constatada em 1996 em Sergipe no município de Boquim, e em 1997 na Bahia, nos municípios de Rio Real e Itapicuru. O objetivo foi revisar a literatura sobre as espécies de cigarrinhas vetores da CVC, e verificar se ocorrem no estado de Sergipe. Os primeiros sintomas são vistos nas folhas, passam posteriormente para os frutos e acabam afetando toda a planta, e para serem percebidos pode levar entre 5 meses e 2 anos. Os principais vetores da X. fastidiosa em citros são as cigarrinhas da família Cicadellidae. No Brasil já foram confirmadas 12 espécies de cigarrinhas vetoras. Para o estado de Sergipe, são escassas a informações sobre Cicadellidae vetoras, os dados são limitados ao Litoral Norte da Bahia, com exceção de vaga citação sobre quatro gêneros (Oncometropia, Acrogonia, Dilobopterus e Homolodisca) e três espécies (Homolodisca ignorata Melichar, Acrogonia sp. e Homolodisca spottii Takiya, Cavichioli & McKamey). Citrus leafhoppers, Vectors of of Bacterium Xylella fastidiosa Wells et al.: Potential Pest of Citrus Crops in Sergipe State Abstract. The citrus industry in Brazil plays a role of great economic, social, generating jobs, income and development. Brazil is the largest producer of citrus, the State of Sergipe stands out in 5th place in national production. Among the many pest problems faced by Brazilian citrus is Citrus Variegated Chlorosis (CVC), known as the yellowing caused by the bacterium Xylella fastidiosa Wells et al. The CVC was officially identified in Brazil in 1987, in orchards of “Triângulo Mineiro” and North and northwest of the state of São Paulo. In the Northeast Region of Brazil, was found in 1996 in the municipality of Boquim Sergipe, and Bahia in 1997, the municipalities of Rio Real and Itapicuru. The aim was to review the literature on the species of leafhoppers vectors of CVC, and verify that occur in the state of Sergipe. The first symptoms are seen in the leaves, then go for the fruits and end up affecting the entire plant, and to be perceived can take between five months and two years. The main vectors of X. fastidiosa in citrus are the sharpshooters of the family Cicadellidae. In Brazil 12 sharpshooters species have already been confirmed. For the state of Sergipe, is scarce information about the Cicadellidae vectors, the data are limited to the northern coast of Bahia, except for vague quote about four genus (Oncometropia, Acrogonia, Dilobopterus and Homolodisca) and three species (Homolodisca ignorata Melichar, Acrogonia sp. and Homolodisca spottii Takiya, Cavichioli & McKamey).

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Dara, Surendra K., Michael R. McGuire, and Harry K. Kaya. "Isolation and Evaluation of Beauveria bassiana (Deuteromycotina: Hyphomycetes) for the Suppression of the Glassy-winged Sharpshooter, Homalodisca coagulata (Homoptera: Cicadellidae)." Journal of Entomological Science 42, no. 1 (2007): 56–65. http://dx.doi.org/10.18474/0749-8004-42.1.56.

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The glassy-winged sharpshooter, Homalodisca coagulata (Say) (Homoptera: Cicadellidae), is a significant threat to California agriculture as a vector of the bacterium, Xylella fastidiosa Wells, causative agent of Pierce's disease. Control strategies target vector populations to prevent the spread of the bacterium. One of the potential means of controlling H. coagulata is the use of entomopathogenic fungi. To discover naturally-occurring fungal pathogens that are adapted to H. coagulata and its habitats, soil samples from organic citrus and conventional pomegranate orchards in Tulare and Riverside counties in southern California were screened for the presence of pathogens. Using a modified Galleria bait method that required small quantities of soil, 124 isolates of Beauveria bassiana (Balsamo) Vuillemin and four isolates of Metarhizium anisopliae (Metschnikoff) Sorokin (Deuteromycotina: Hyphomycetes) were recovered. Additionally, 22 isolates of B. bassiana were recovered by plating soil suspensions on selective growth media. Natural fungal infections were not detected in H. coagulata populations from periodic sampling in Kern, Riverside and Ventura counties in southern California. Some of the B. bassiana isolates recovered from soil and other insect hosts in southern California were evaluated against H. coagulata along with those isolated from H. coagulata in Texas and Mississippi. Growth of the selected isolates also was evaluated at 15, 23, 28 and 32°C. The Texas isolate and two California isolates of B. bassiana were virulent against H. coagulata and warrant further study.

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Dellapé, Gimena, Guillermo A. Logarzo, Eduardo G. Virla, and Susana L. Paradell. "New Records on the Geographical Distribution of South American Sharpshooters (Cicadellidae: Cicadellinae: Proconiini) and their Potential as Vectors ofXylella fastidiosa." Florida Entomologist 94, no. 2 (2011): 364–66. http://dx.doi.org/10.1653/024.094.0239.

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Krugner, R., C. A. Ledbetter, J. Chen, and A. Shrestha. "Phenology of Xylella fastidiosa and Its Vector Around California Almond Nurseries: An Assessment of Plant Vulnerability to Almond Leaf Scorch Disease." Plant Disease 96, no. 10 (2012): 1488–94. http://dx.doi.org/10.1094/pdis-01-12-0017-re.

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Management of almond leaf scorch disease requires knowledge of all possible infection pathways. The disease is caused by the xylem-limited bacterium Xylella fastidiosa, which is transmitted by several species of sharpshooters. The objectives of this research were to elucidate the fate of bacteria in planta after inoculations in almond nursery plants and to determine patterns of insect vector population dynamics and temporal distribution of X. fastidiosa–infected plants relative to host plant assemblages in habitats surrounding commercial nurseries. In an experimental nursery, disease incidence was markedly affected by rootstock type. Prior to bud grafting, ‘Nemaguard’ rootstock seedlings were not susceptible to bacterial infection. After bud grafting with a susceptible scion (‘Sonora’), scions were susceptible to infection regardless of rootstock genotype. Surveys near commercial nurseries revealed that only habitats with permanent grass cover sustained vector populations throughout the season. A total of 87 plant samples tested positive for X. fastidiosa (6.3%) using enzyme-linked immunosorbent assay (ELISA), with a higher number of X. fastidiosa–infected plants found in weedy alfalfa fields than in other habitat types. Among plant species infected by X. fastidiosa, 33% were winter annuals, 45% were biennials or perennials, and 22% were summer annuals. Collectively, these findings identified a potential pathway for X. fastidiosa infection of almonds in nursery situations.

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Azizi, Armaghan, Arinder Arora, Anatoliy Markiv, David J. Lampe, Thomas A. Miller, and Angray S. Kang. "Ribosome Display of Combinatorial Antibody Libraries Derived from Mice Immunized with Heat-Killed Xylella fastidiosa and the Selection of MopB-Specific Single-Chain Antibodies." Applied and Environmental Microbiology 78, no. 8 (2012): 2638–47. http://dx.doi.org/10.1128/aem.07807-11.

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ABSTRACTPierce's disease is a devastating lethal disease ofVitus viniferagrapevines caused by the bacteriumXylella fastidiosa. There is no cure for Pierce's disease, and control is achieved predominantly by suppressing transmission of the glassy-winged sharpshooter insect vector. We present a simple robust approach for the generation of panels of recombinant single-chain antibodies against the surface-exposed elements ofX. fastidiosathat may have potential use in diagnosis and/or disease transmission blocking studies.In vitrocombinatorial antibody ribosome display libraries were assembled from immunoglobulin transcripts rescued from the spleens of mice immunized with heat-killedX. fastidiosa. The libraries were used in a single round of selection against an outer membrane protein, MopB, resulting in the isolation of a panel of recombinant antibodies. The potential use of selected anti-MopB antibodies was demonstrated by the successful application of the 4XfMopB3 antibody in an enzyme-linked immunosorbent assay (ELISA), a Western blot assay, and an immunofluorescence assay (IFA). These immortalizedin vitrorecombinant single-chain antibody libraries generated against heat-killedX. fastidiosaare a resource for the Pierce's disease research community that may be readily accessed for the isolation of antibodies against a plethora ofX. fastidiosasurface-exposed antigenic molecules.

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Feil, Helene, William S. Feil, and Alexander H. Purcell. "Effects of Date of Inoculation on the Within-Plant Movement of Xylella fastidiosa and Persistence of Pierce's Disease Within Field Grapevines." Phytopathology® 93, no. 2 (2003): 244–51. http://dx.doi.org/10.1094/phyto.2003.93.2.244.

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The effects of date of inoculation on the development of Pierce's disease (PD) were evaluated in California grapevines during 1997 through 2000 at four locations. Some vines that had been inoculated either by using blue-green sharpshooters (Graphocephala atropunctata) as vectors or mechanically by needle puncture with the PD causal bacterium Xylella fastidiosa became infected during each month and at each location where infection was attempted. Vines inoculated on the earliest inoculation dates (April to May) developed more extensive and severe PD symptoms, and only 54% of these vines recovered from PD after the following winter, compared with vines that had been inoculated during June through August, of which 88% recovered from PD after the following winter. For the 1999 inoculations, the number of vines infected at a central California site (Parlier) was higher than the number of vines infected at a north coastal site (Hopland). For the best-fitting regression equation, percent recovery of vines infected with X. fastidiosa increased significantly with date of inoculation (r2 = 0.737) at all sites excluding Hopland. The Hopland site had the highest percentage of vines that recovered from PD (100%). At most sites, only early infection (April and May) resulted in chronic disease unless the vines were inoculated at the bases instead of the distal tips of canes. Vines inoculated early in the growing season (April and May) have less chance to recover from Pierce's disease than vines inoculated later (July and August).

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Manzano, Carolina, Graciela Benzal, Guillermo A. Logarzo, Maria V. Coll Araoz, Eduardo G. Virla, and Erica Luft Albarracin. "Biological traits of Cosmocomoidea annulicornis (Hymenoptera: Mymaridae), an egg parasitoid of the sharpshooter Tapajosa rubromarginata (Hemiptera: Cicadellidae), a vector of Xylella fastidiosa in citrus orchards." Biological Control 157 (June 2021): 104589. http://dx.doi.org/10.1016/j.biocontrol.2021.104589.

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FROZA, JOYCE A., VICTOR QUINTAS, and GABRIEL MEJDALANI. "A new species of Erythrogonia Melichar, 1926 (Insecta: Hemiptera: Cicadellidae: Cicadellini) from the Mantiqueira mountain range, southeastern Brazil, associated with olive orchards." Zootaxa 4996, no. 2 (2021): 374–82. http://dx.doi.org/10.11646/zootaxa.4996.2.11.

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A new species of the diverse Neotropical sharpshooter genus Erythrogonia Melichar, 1926 is described and illustrated from the Mantiqueira mountain range, municipality of Maria da Fé, state of Minas Gerais, southeastern Brazil. The new taxon is associated with olive orchards and has been implicated as a vector of the bacterium Xylella fastidiosa Wells et al., 1987, which causes a disease known in Brazil as olive leaf scorch syndrome. Erythrogonia sinvali sp. nov. can be distinguished from the other 90 known species of the genus by the following combination of features: (1) crown black without conspicuous contrasting spots; (2) frons with large yellow median spot; (3) pronotum black with large yellow area covering most of disk; (4) forewing dark red, without contrasting spots or stripes, costal margin narrowly black, apical portion dark brown; (5) aedeagus elongate, curved dorsally, with pair of spiniform apical processes; (6) paraphyses greatly reduced; (7) basal portion of male anal tube with pair of spiniform curved processes; (8) posterior margin of female abdominal sternite VII broadly emarginate and with broad central lobe; (9) female sternite VIII with sclerotized areas, including a transverse bar located at bases of ovipositor valvulae I, followed by a pair of elongate sclerites and a posterior bilobed sclerite. Both males and females of the new species are described in detail. A putative group of five species within Erythrogonia is preliminarily proposed, including the new taxon, E. separata Melichar, 1926, E. dorsalis (Signoret, 1853), E. calva (Taschenberg, 1884), and E. melichari Schmidt, 1928. Among these species, the male terminalia of E. sinvali sp. nov. are more similar to those of E. separata.

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White, Daniel, Elaine A. Backus, Ian M. Marcus, Sharon L. Walker, and M. Caroline Roper. "Functional foregut anatomy of the blue–green sharpshooter illustrated using a 3D model." Scientific Reports 11, no. 1 (2021). http://dx.doi.org/10.1038/s41598-021-85954-4.

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AbstractSharpshooter leafhoppers (Hemiptera: Cicadellidae: Cicadellinae) are important vectors of the plant pathogenic bacterium Xylella fastidiosa Wells et al. (Xanthomonadales: Xanthomonadaceae). This pathogen causes economically significant diseases in olive, citrus, and grapes on multiple continents. Bacterial acquisition and inoculation mechanisms are linked to X. fastidiosa biofilm formation and fluid dynamics in the functional foregut of sharpshooters, which together result in egestion (expulsion) of fluids likely carrying bacteria. One key X. fastidiosa vector is the blue–green sharpshooter, Graphocephala atropunctata (Signoret, 1854). Herein, a 3D model of the blue–green sharpshooter functional foregut is derived from a meta-analysis of published microscopy images. The model is used to illustrate preexisting and newly defined anatomical terminology that is relevant for investigating fluid dynamics in the functional foregut of sharpshooters. The vivid 3D illustrations herein and supplementary interactive 3D figures are suitable resources for multidisciplinary researchers who may be unfamiliar with insect anatomy. The 3D model can also be used in future fluid dynamic simulations to better understand acquisition, retention, and inoculation of X. fastidiosa. Improved understanding of these processes could lead to new targets for preventing diseases caused by X. fastidiosa.

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Backus, Elaine A., and Hsien-Tzung Shih. "Do Sharpshooters From Around the World Produce the Same EPG Waveforms? Comparison of Waveform Libraries From Xylella fastidiosa (Xanthomonadales: Xanthomonadaceae) Vectors Kolla paulula (Hemiptera: Cicadellidae) From Taiwan and Graphocephala atropunctata From California." Journal of Insect Science 20, no. 4 (2020). http://dx.doi.org/10.1093/jisesa/ieaa056.

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Abstract When an exotic invasive species is a vector-borne plant pathogen, vector feeding behavior must be studied to identify potential host plant range and performance of specialized pathogen transmission behaviors. The most rigorous tool for assessing vector feeding behavior is electropenetrography (EPG). Xylella fastidiosa Wells et al. is a gram-negative bacterium native to the Americas, where it is the causal agent of lethal scorch-type diseases such as Pierce’s disease (PD) of grapevines. In 2002, a PD strain of X. fastidiosa invaded Asia for the first time, as confirmed from grape vineyards in Taiwan. Kolla paulula (Wallker), a native Asian species of sharpshooter leafhopper, was found to be the primary vector in Taiwanese vineyards. This study used an AC-DC electropenetrograph to record stylet probing behaviors of K. paulula on healthy grapevines. The main objective was to create an EPG waveform library for K. paulula. Waveform description, characterization of R versus emf components (electrical origins), and proposed biological meanings of K. paulula waveforms are reported. In addition, comparison of K. paulula waveforms with those from the most efficient, native vector of X. fastidiosa in California vineyards, Graphocephala atropunctata, is also reported. Overall, both species of sharpshooters had similar-appearing waveforms. Five new findings were identified, especially that the previously described but rare waveform subtype, B1p, was extensively produced in K. paulula recordings. Sharpshooter waveforms from species worldwide share a high degree of similarity. Thus, EPG methods can be rapidly applied to potential vectors where X. fastidiosa is newly introduced.

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Bassanezi, Renato Beozzo, and Isabela V. Primiano. "Huanglongbing and citrus variegated chlorosis integrated management based on favorable periods for vector population increase and symptom expression." Plant Disease, March 17, 2021. http://dx.doi.org/10.1094/pdis-06-20-1359-re.

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Huanglongbing (HLB, associated with ‘Candidatus Liberibacter asiaticus’ and transmitted by the Asian citrus psyllid Diaphorina citri) and citrus variegated chlorosis (CVC, caused by Xylella fastidiosa subsp. pauca and transmitted by sharpshooter species) have been managed by vector control and removal of symptomatic trees. Although vectors and new symptomatic trees can be detected year-round, peaks of vector populations are higher in spring and summer and the most symptomatic trees are found in autumn and winter. This work aimed to compare the management of both diseases during these favorable periods. The experiment was conducted over five years in a commercial orchard and had a 3 by 2 factorial design. The factor “vector control” had 3 levels: monthly vector control year-round (VCYR); monthly vector control in spring and summer (VCSS); and vector control when a threshold level of 10% occupancy was detected (VCOT). The factor “inoculum removal” had 2 levels: monthly eradication year-round (TEYR); and monthly eradication in autumn and winter (TEAW). Host flush, both HLB and CVC vector populations, and the number of symptomatic citrus plants were visually assessed. The level of vectors over the seasons, as measured using the average area under the curve (AUC), was similar for all treatments with the exception of psyllid abundance, which was around 4.5 times higher for VCSS than other treatments. For both diseases, no difference in the average AUC of disease progress and disease final incidence was observed. VCOT or adjusted VCSS associated to TEAW could be integrated for sustainable citrus production.

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