Sharpshooter Species Research Articles

Phylogeny and biogeography of the sharpshooters (Hemiptera: Cicadellidae: Cicadellinae)

AbstractSharpshooters (Cicadellinae), a large subfamily of the Cicadellidae, exhibit a global distribution and a broad array of ecological preferences. To explore the phylogenetic relationships and roles of global historical, biotic and biogeographic processes in the diversification of sharpshooters, we analysed DNA sequence data from three mitochondrial and two nuclear genes for 243 taxa representing all Cicadellinae tribes, generic groups, regional faunas and data of geographic distributions of sharpshooter species compiled from online databases and available literature. The maximum likelihood (ML) and Bayesian inference (BI) analyses strongly support the monophyletic clade including Cicadellinae and Phereurininae. Divergence time estimates and biogeographic analyses suggest that sharpshooters originated in the Neotropical region or were more widespread in Gondwana during the Early Cretaceous and diversified through a combination of ancient vicariance and dispersal following the evolution of angiosperm‐dominated habitats. The earliest divergence during the Cretaceous gave rise to Oriental and New World lineages, the latter of which subsequently dispersed into the Old World and gave rise to the diverse endemic fauna of Madagascar. The Oriental lineage shows high diversity and endemism in tropical Asia and the Pacific, with striking distributional discontinuities in Wallacea. These results suggest that a combination of environmental and evolutionary factors including continental‐scale vicariance, long‐distance dispersal and diversification of terrestrial microhabitats and host plants may explain the diversity of the modern sharpshooter fauna.

Huanglongbing and Citrus Variegated Chlorosis Integrated Management Based on Favorable Periods for Vector Population Increase and Symptom Expression.

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 during 5 years in a commercial orchard and had a three-by-two factorial design. The factor "vector control" had three 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 two 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 approximately 4.5 times higher for VCSS than for 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 with TEAW could be integrated for sustainable citrus production.

Identification of candidate insect vectors of Grapevine red blotch virus by means of an artificial feeding diet

The ability of an insect to vector a plant virus has traditionally been determined through controlled greenhouse transmission experiments that are notoriously resource- and time-consuming and of unreliable outcome. Therefore, before committing to these protracted experiments, it is important that researchers identify biologically viable candidate vectors. This study presents an approach for identifying potential insect vectors of circulative plant viruses that significantly reduces the time-to-results while also reducing costs and required resources. This artificial transmission protocol, using a buffered sucrose solution as the virus recipient in place of a living plant, also eliminates plant-to-plant variation in susceptibility to infection, allowing assessment of virus–insect compatibility required for successful transmission of persistent viruses. To validate this approach, species of hemipteran insects, including leafhoppers, froghoppers, aphids, sharpshooters, and treehoppers, were subjected to an artificial feeding system to determine their ability to vector the emerging Grapevine red blotch virus (GRBV) (family: Geminiviridae). Test insects were allowed to feed on a potted grapevine infected with GRBV for 3 days and then transferred to tubes containing the sucrose solution partitioned by a thinly stretched Parafilm™ membrane. After 3 days of feeding through the membrane, viruliferous test insects were stored for species identification and the sucrose solutions were tested by conventional polymerase chain reaction for the presence of GRBV DNA. Out of all the insects tested (n = 395) only nine treehoppers from two different species successfully transmitted GRBV to the sucrose solutions, indicating a high likelihood of vector capability, to be validated by greenhouse or field experiments.

First sharpshooter species proven as vectors of Xylella fastidiosa subsp. multiplex in Prunus salicina trees in Brazil

Plum leaf scald (PLS), caused by the vector-borne bacterium Xylella fastidiosa, is a major obstacle to the expansion of plum crops in Brazil. In other affected crops, this pathogen is naturally transmitted mainly by sharpshooter leafhoppers (Hemiptera: Cicadellidae: Cicadellinae). Despite the importance of PLS, the vector species responsible for bacterial spread in plums remain unknown. This study, therefore, aimed to determine the X. fastidiosa transmission ability of three sharpshooter species commonly found in plum orchards in southern and southeastern Brazil: Macugonalia cavifrons (Stål), Macugonalia leucomelas (Walker), and Sibovia sagata (Signoret). After a 72-h acquisition access period to plum trees infected with X. fastidiosa subsp. multiplex (sequence type 67), the insects were transferred for an inoculation access period of 96 h to 10–20 healthy Prunus salicina plants for each sharpshooter species, using four insects per plant. Bacterial infection in the plants was verified 7 months after inoculation by polymerase chain reaction. Results showed that the three sharpshooter species were able to transmit X. fastidiosa to plums, with mean transmission efficiencies by single insects of 16%, 14%, and 18% for M. cavifrons, M. leucomelas, and S. sagata, respectively. To our knowledge, this study is the first to identify vector species and prove the transmission of a PLS strain of X. fastidiosa subsp. multiplex by sharpshooters in Brazil.

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.

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.

Tretogonia Melichar (Hemiptera: Cicadellidae: Proconiini): two new species from South Brazil and a description of T. dentalis Emmrich, 1988

Two new Brazilian sharpshooter species of the genus Tretogonia Melichar, 1926 are described and illustrated: Tretogonia diminuta sp. nov. and T. elegantula sp. nov., both from the State of Paraná. A redescription of T. dentalis Emmrich, 1988 is provided based on a male from the State of Mato Grosso do Sul. This is the first Brazilian record of T. dentalis, a species originally described from Paraguay. Photographs and line drawings are provided for the three species, as well as notes on the taxonomy and biology of the genus.

Transmission Efficiency of Xylella fastidiosa subsp. pauca Sequence Types by Sharpshooter Vectors after In Vitro Acquisition.

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.

Three new Brazilian species of the sharpshooter genus Geitogonalia Young (Hemiptera: Cicadellidae: Cicadellini).

Three new Brazilian sharpshooter species of the genus Geitogonalia Young, 1977 are described: G. buccina sp. nov., G. piei sp. nov., and G. tetracorni sp. nov. The first species is known from the states of Rio de Janeiro and Minas Gerais, whereas the second and third species are from the state of Paraná. We provide descriptions of the male and female (except for G. piei), photographs and illustrations, as well as a revised diagnosis of the genus and a key to the five known species.

A new species of Cardioscarta (Hemiptera: Cicadellidae: Cicadellini) fromthe Atlantic Forest of southeastern Brazil and key to species of the genus.

The South American genus Cardioscarta Melichar, 1932 includes seven species of colorful sharpshooters. Here we describe and illustrate an additional species, C. aurantia sp. nov., from the Atlantic Forest of southeastern Brazil (state of Rio de Janeiro). The new taxon can be distinguished by the dark brown to black forewing with two large orange areas, one from basal portion of corium to distal portions of discal cells and another covering most of clavus, or with single large orange area on basal two-thirds. A key to species of Cardioscarta is provided and the new species is compared with the other ones of the genus.

De novo transcriptome assemblies of four xylem sap-feeding insects.

Background: Spittle bugs and sharpshooters are well-known xylem sap-feeding insects and vectors of the phytopathogenic bacterium Xylella fastidiosa (Wells), a causal agent of Pierce's disease of grapevines and other crop diseases. Specialized feeding on nutrient-deficient xylem sap is relatively rare among insect herbivores, and only limited genomic and transcriptomic information has been generated for xylem-sap feeders. To develop a more comprehensive understanding of biochemical adaptations and symbiotic relationships that support survival on a nutritionally austere dietary source, transcriptome assemblies for three sharpshooter species and one spittlebug species were produced. Findings: Trinity-based de novo transcriptome assemblies were generated for all four xylem-sap feeders using raw sequencing data originating from whole-insect preps. Total transcripts for each species ranged from 91 384 for Cuerna arida to 106 998 for Homalodisca liturata with transcript totals for Graphocephala atropunctata and the spittlebug Clastoptera arizonana falling in between. The percentage of transcripts comprising complete open reading frames ranged from 60% for H. liturata to 82% for C. arizonana. Bench-marking universal single-copy orthologs analyses for each dataset indicated quality assemblies and a high degree of completeness for all four species. Conclusions: These four transcriptomes represent a significant expansion of data for insect herbivores that feed exclusively on xylem sap, a nutritionally deficient dietary source relative to other plant tissues and fluids. Comparison of transcriptome data with insect herbivores that utilize other dietary sources may illuminate fundamental differences in the biochemistry of dietary specialization.

Description of the female terminalia of twelve species of Proconiini and a key to genera from Argentina (Insecta: Hemiptera: Cicadellidae).

The female terminalia of 12 sharpshooter species are described and illustrated: Aulacizes basalis, A. conspersa, A. insistans, A. obsoleta, A. quadripunctata, Cicciana latreillei, Pseudometopia amblardii, Stictoscarta sulcicollis, Tretogonia bergi, T. cribata, T. dentalis, and T. notatifrons. A key to the identification of the Argentinean Proconiini genera including male and female characters is provided.

Xylella fastidiosa Transmission and Life History of Two Cicadellinae Sharpshooters, Kolla paulula and Bothrogonia ferruginea (Hemiptera: Cicadellidae), in Taiwan.

Xylella fastidiosa causes Pierce's disease (PD) and is transmitted by xylem-sap-feeding insects. While X. fastidiosa -infected grapevines have been detected, the transmission vectors reported have never been recorded in Taiwan. Previous studies have suggested that Kolla paulula (Walker) and Bothrogonia ferruginea (F.) are candidate vectors in Taiwan. Here, we explored the life history of these two leafhoppers, evaluated the transmission efficiency of X. fastidiosa by the vectors, and investigated the genetic identity of three collected X. fastidiosa strains, namely, GMb, BQa, and BQ7f from the grapevine cultivars Golden Muscat (GM) and Black Queen (BQ), and one previously extracted strain GV148 from Kyoho (GV) showing PD symptoms in local vineyards. The results showed that all four strains were 100% identical to X. fastidiosa isolate Temecula1 from a naturally infected grapevine in the United States based on sequence analyses of 16S rRNA and 16S-23S ITS. The acquisition rates by K. paulula and B. ferruginea from the symptomatic cultivar Golden Muscat were 83.3 and 70.0% per individual, and the transmission rates to healthy grapevines were 13.3 and 6.7%, respectively. The acquisition rates by the groups of three K. paulula from the symptomatic cultivars Golden Muscat and Black Queen were 54.7 and 49.6%, respectively. Additionally, the transmission rates by K. paulula from and to each of these two grapevine cultivars were not significantly different. In view of their acquisition from infected grapevines and the effective transmission of X. fastidiosa to healthy grapevines, these two sharpshooter species are vectors of X. fastidiosa in Taiwan.

Three new species of Fonsecaiulus (Hemiptera, Cicadellidae, Cicadellini) from Brazil and key to species of the genus.

Three new sharpshooter species of the genus Fonsecaiulus Young, 1977 are described and illustrated from specimens collected in the Brazilian Atlantic Forest, Fonsecaiulus rectangularis and Fonsecaiulus guttiformis, and in the Brazilian Cerrado, Fonsecaiulus filiformis. The descriptions are based on features from the external morphology, color pattern, and male and female genital structures. Comparisons of the three new taxa with the remaining six Fonsecaiulus species are provided. An identification key to males of all known species of the genus is given.

A new species and key to species of the agriculturally important sharpshooter genus Sonesimia Young (Hemiptera: Cicadellidae: Cicadellini)

The new sharpshooter species Sonesimia nessimiani is described from Bolivia based on specimens collected on sugar cane. An identification key to males and females of all known species of the genus is given. In addition to the external morphology, color pattern, and male genitalia, female genital structures are also described and illustrated. Notes comparing the new species with the remaining six Sonesimia species are provided.

Phenology of Xylella fastidiosa and Its Vector Around California Almond Nurseries: An Assessment of Plant Vulnerability to Almond Leaf Scorch Disease.

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.

Vector preference for hosts differing in infection status: sharpshooter movement and Xylella fastidiosa transmission

1. Epidemiological theory predicts that vector preference for hosts differing in infection status (i.e. healthy or infected) affects disease dynamics.2. Numerous studies have documented strong vector preference for or discrimination against infected hosts. However, the significance of these behaviours for pathogen transmission and spread has been poorly described.3. We conducted a series of choice assays to evaluate orientation preference, feeding preference, and movement rates of an important group of vectors, the sharpshooter leafhoppers, based on host infection status for the generalist plant pathogen, Xylella fastidiosa Wells et al.4. Sharpshooters did not discriminate between healthy versus infected‐but‐asymptomatic grapevines, but they oriented preferentially to healthy grapevines more frequently than either symptomatic vines or those artificially coloured to mimic disease symptoms.5. In a field trial three sharpshooter species showed different movement rates and preferences for feeding site, but all species exhibited similar and significant preference for healthy hosts.6. Although there was no significant difference in acquisition efficiency among vector species, those individuals that spent more time on healthy hosts tended to be less likely to acquire the pathogen.7. These results suggest that sharpshooters discriminate against infected grapevines, which are likely to be of poorer quality, with visual cues playing a role in host selection. Preference by these vectors may affect pathogen acquisition, which could affect disease spread in the field.

Comparative Behavioral and Protein Study of Salivary Secretions in Homalodisca spp. Sharpshooters (Hemiptera: Cicadellidae: Cicadellinae)

Abstract A novel brush-induced method to physically stimulate salivation was applied to the glassy-winged and smoke tree sharpshooters (Hemiptera: Cicadellidae: Cicadellinae). This technique enabled the direct observation of salivary secretion processes, solidification of saliva, and collection of salivary secretions. For both species, brush-induced saliva was first secreted in liquid form, a portion of which gradually solidified to form the salivary sheath for both sharpshooter species. Proteins of similar molecular weight were obtained from brush-induced saliva extracts from both sharpshooters. Extracts from dried sheaths collected from Parafilm membranes over artificial diet had a different protein profile from brush-induced saliva extracts. The latter contained fewer proteins than extracts of the liquid content of salivary glands. Two proteins appeared in all three of the extracts from hemolymph, salivary glands, and brush-induced saliva, one of which also appeared in dried sheath extracts. Our findings support previous research by others that there is a limited flow of protein from hemolymph to salivary glands and brush-induced saliva. There is also some protein modification associated with saliva solidification. The quantity and composition of proteins suggest the brushinduced saliva collection method has merit for future biochemical analyses of saliva. The implications of this work could potentially include illuminating the mechanism of inoculation by the Pierce's disease bacterium, Xylella fastidiosa.

Endophytic Bacteria Associated to Sharpshooters (Hemiptera: Cicadellidae), Insect Vectors of Xylella fastidiosa Subsp. pauca

Xylella fastidiosa subsp. pauca causes citrus variegated chlorosis (CVC) disease in Brazil, resulting in significant production losses in the citrus industry. X. fastidiosa subsp. pauca is mainly transmitted by three species of sharpshooters (Hemiptera: Cicadellidae) in Brazil; Dilobopterus costalimai (Young), Acrogonia citrina Marucci & Cavichioli and Oncometopia facialis (Signoret). We identified bacterial communities associated with the heads of surface-sterilized insect vectors of X. fastidiosa subsp. pauca that were collected from CVC affected citrus groves in Brazil. Bacteria were isolated and analyzed by amplified ribosomal DNA restriction analysis (ARDRA) and sequencing, revealing the presence, among the most abundant genera, of the well-known citrus endophytes Methylobacterium spp. and Curtobacterium spp. Specific PCR systems for the detection of these genera indicated high frequencies of presence of these bacteria in sharpshooters. The remaining bacterial community was compared in distinct vector species and at different period of the year by denaturing gradient gel electrophoresis (DGGE), showing its responsiveness to the climate change over the year. These results represent a new basis for the knowledge about the interaction symbiotic-pathogenic bacteria inside insect vectors and provide a basis for further work on the biocontrol of plant bacteria like X. fastidiosa.

Seasonal Occurrence and Abundance of Sharpshooter Leafhoppers in Alabama Orchards and Vineyards

Although the bacterium Xylella fastidiosa (Xf) has been confirmed to cause economic losses to numerous fruit crop species in the southeastern U.S. since 1933, no science-based information is available on the occurrence of infection in economic fruit crops grown in Alabama, as well as the presence of effective Xf vectors in the state. An investigation to identify the sharpshooter (Hemiptera: Cicadellidae) fauna and to determine their occurrence in selected orchards and vineyards was conducted in Alabama during 2008–2009. Leafhoppers were trapped in three different geographic locations: in the Gulf Coast, Central, and North Alabama. Seven species of sharpshooters were identified, including: Homalodisca vitripennis (Germar), H. insolita (Walker), Oncometopia orbona (Fabricius), Paraulacizes irrorata (Fabricius), Graphocephala coccinea (Forster), Graphocephala versuta (Say), and Draeculacephala spp. H. vitripennis and G. versuta were the most prevalent species in Alabama orchards and vineyards; however, their proportion varied by location. H. vitripennis was the most abundant species trapped in the Gulf Coast area, whereas G. versuta was the most prevalent sharpshooter species in Central and North Alabama. The results are discussed in relation to the likelihood and efficiency of these species as Xf vectors in Alabama.

Populations of Sharpshooters in Two Citrus Groves in East-central Florida as Indicated by Yellow Sticky Card Traps

Populations of Sharpshooters in Two Citrus Groves in East-central Florida as Indicated by Yellow Sticky Card Traps