Oncometopia Facialis Research Articles

Diversity, population fluctuation and faunistic analysis of sharpshooters (hemiptera: Cicadellidae: Cicadellinae) in plum orchards in Videira, Santa Catarina, Brazil

Sharpshooters are known vectors of Plum Leaf Scald, caused by Xylella fastidiosa. The present study assessed diversity, population fluctuation and faunistic analysis in two plum orchards in Santa Catarina – Brazil, from January 2011 to December 2012. Traps were installed at 10 equidistant points in each orchard: two traps, high and low, at each sampling point. Cicadellini were the most abundant tribe, with 15 species, seven of them potential vectors (Bucephalogonia xanthophis, Dilobopterus costalimai, Hortensia similis, Macugonalia cavifrons, Macugonalia leucomelas, Pawiloma gratiosa, and Sibovia sagata) and a total of 759 specimens. In Proconiini, six species were captured, including two potential vectors (Homalodisca ignorata and Oncometopia facialis), and a total of 226 specimens. Dominant species were Erythrogonia dorsalis, M. cavifrons, O. fusca, B. xanthophis, and O. facialis. Constant species were E. dorsalis, M. cavifrons, S. sagata, O. facilis, and O. fusca. In Cicadellini, 104 specimens were caught on high traps (11 species) and 655 on low traps (15). In Proconiini, 59 specimens on high traps (6) and 167 on low traps (4). The composition and community diversity were distinct when comparing the sampled orchards, according to Shannon and Equitability Indexes, Effective Number of Species, and Hutcheson t-Test. Cicadellinae population peak was in April for 2011, 2012 altogether. Dominant species population peaks were in February (E. dorsalis), April (M. cavifrons), July (B. xanthophis), September (O. facialis), and October (O. fusca). Population fluctuation is likely affected by biotic and abiotic factors, especially human activity and plant phenology.

Comparison of protocols for the extraction of genomic DNA from Sharpshooters (Hemiptera: Cicadellidae) for the detection of Xylella fastidiosa

ABSTRACT: The bacterium Xylella fastidiosa, the causal agent of citrus variegated chlorosis (CVC), is dependent on vector insects for its spread and infection of citrus hosts. The insects, leafhoppers (Hemiptera: Cicadellidae) transmit the bacteria to healthy plants after feeding on infected plants. The objective of this study was to develop and compare methods for extracting genomic DNA from sharpshooters to detect X. fastidiosa. The DNA extraction from insects was performed according to a phenol-chloroform based DNA extraction in conjunction with two commercial kits, Dneasy® Plant Mini Kit and blood & tissue Dneasy® Handbook (Qiagen Inc., Valencia, CA, USA). The heads of the following species of sharpshooter were used: Dilobopterus costalimai, Acrogonia citrina, Oncometopia facialis, Bucephalogonia xanthophis, Macugonalia leucomelas and Homalodisca ignorata. Based on the numeric differences between independent samples, the results showed the use of the phenol:chloroform extraction method (36/50 positives) and the DNeasy® Plant Mini Kit (33/50) resulting in the most detections of X. fastidiosa from leafhopper samples. As these two methods detected Xylella in the greatest number of infected samples, they may be more efficient to use for detection purposes in leafhoppers.

Population Fluctuation and Faunistic Analysis of Sharpshooters (Hemiptera: Cicadellidae: Cicadellinae) in Plum Orchards in the Municipality of Protásio Alves, Rio Grande do Sul State, Brazil

Plum cultivation in Brazil is of great economic importance, especially in the state of Rio Grande do Sul; however, orchards of this fruit have suffered great losses in productivity due to the Plum Leaf Scald disease caused by the bacterium Xylella fastidiosa Wells et al., 1987, transmitted by sharpshooter vectors (Hemiptera: Cicadellidae: Cicadellinae). The aim of this study was to understand the population fluctuation and faunistic analysis of Cicadellinae. Sampling was conducted in two areas of Prunus salicina Lindl., New Orchard and Old Orchard, from May 2011 to May 2013. Sharpshooters were collected using 40 yellow sticky traps in 20 collecting points. At each point, two traps were installed (high and low). Twenty-one species were identified, including eight potencial vector species (*): Cicadellini - Bucephalogonia xanthophis*, Caragonalia carminata, Diedrocephala bimaculata, Dilobopterus dispar, Erythrogonia dorsalis, Erythrogonia separata, Hortensia similis*, Macugonalia cavifrons*, Macugonalia geographica, Pawiloma victima, Sibovia sagata* and Sonesimia grossa*; Proconiini - Aulacizes obsoleta, Homalodisca ignorata*, Molomea confluens, Molomea consolida*, Molomea lineiceps, Molomea personata, Oncometopia facialis*, Oncometopia fusca and Tapajosa rubromarginata. Cicadellini was mainly captured in low traps (222 captures) and Proconiini in high traps (59 captures). Seven taxa were classified as dominant and frequent: B. xanthophis, D. dispar, E. dorsalis, M. cavifrons, S. sagata, O. facialis and O. fusca. The population fluctuation peak for 2011 was May (62 specimens); for 2012, June (42); and for 2013, April (13). The population of sharpshooters in the orchard is directly influenced by abiotic and biotic factors, decreasing drastically during hotter and drier months, during extreme meteorological fluctuation and on periods of increased human activity. The difference in trap height is important since each tribe displays different feeding behaviors in relation to the strata, thereby providing a broad sampling of species to better understand the role of vectors in transmitting the bacteria.

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.

Análise faunística de cigarrinhas (Hemiptera: Cicadellidae) na cultura da videira no Rio Grande do Sul

In some American countries, grapevines are affected by Pierce's disease (PD), which is caused by a particular strain of Xylella fastidiosa not yet reported in Brazil. In order to investigate the potential for PD spread in Brazil in case of pathogen introduction, we conducted a faunistic analysis of leafhoppers (Hemiptera: Cicadellidae) associated to vineyards in the State of Rio Grande do Sul, with emphasis in the subfamily Cicadellinae (sharpshooters), which includes the main potential vectors of X. fastidiosa. Leafhopper samplings were carried out fortnightly during two years (9/2004-9/2006) in four Vitis vinifera vineyards in the municipalities of Bento Gonçalves and Farroupilha (RS). Thirtyfour leafhopper and six spittlebug species were collected, but most (98.4%) of the 3,893 specimens trapped were leafhoppers, distributed in the subfamilies Cicadellinae (60.2%), Gyponinae (34.1%), Deltocephalinae (3.8%) and Coelidinae (0.3%). The sharpshooter specimens were divided in the tribes Cicadellini (68.5%; 12 species) and Proconiini (31.5%; 11 species). Based on the faunistic indices, five species of Cicadellini, Bucephalogonia xanthophis (Berg), Dilobopterus dispar (Germar), Macugonalia cavifrons Stal, Sibovia sagata (Signoret) and Spinagonalia rubrovittata Cavichioli, and three of Proconiini, Molomea consolida (Schöder), Oncometopia facialis (Signoret) and Oncometopia fusca Melichar were prevalent in the vineyards. The high diversity of native sharpshooters in Rio Grande do Sul indicates the existence of a high risk of PD spread if the pathogen is introduced in grapevines.

Transmission Efficiency of <I>Xylella fastidiosa</I> by Sharpshooters (Hemiptera: Cicadellidae) in Coffee and Citrus

Xylella fastidiosa (Wells, Raju, Hung, Weisburg, Mandelco-Paul, and Brenner) is a bacterial pathogen transmitted by several sharpshooters in two tribes of Cicadellinae (Proconiini and Cicadellini). Here, we compared the transmission efficiency of X. fastidiosa in coffee (Coffea arabica L.) and citrus [Citrus sinensis (L.) Osbeck] by Cicadellini [Bucephalogonia xanthophis (Berg) and Dilobopterus costalimai Young] and Proconiini [Homalodisca ignorata Melichar and Oncometopia facialis (Signoret)] sharpshooters that occur in both crops. At different seasons, healthy adults of each species were submitted to a 48-h acquisition access period on citrus or coffee source plants infected with X. fastidiosa isolates that cause Citrus variegated chlorosis (CVC) and Coffee leaf scorch (CLS), respectively, and then confined on healthy seedlings of the corresponding host plant for a 48-h inoculation access period. No significant effect of inoculation season was observed when comparing infection rates of citrus or coffee plants inoculated by vectors at different times of the year. In citrus, the transmission rate by single insects was significantly higher for H. ignorata (30%) in relation to B. xanthophis (5%) and O. facialis (1.1%), but there was no difference among vector species in coffee, whose transmission rates ranged from 1.2 to 7.2%. Comparing host plants, H. ignorata was more effective in transmitting X. fastidiosa to citrus (30%) in relation to coffee (2.2%), whereas the other vectors transmitted the bacterium to both hosts with similar efficiencies. Despite these variations, vector efficiency in coffee and citrus is lower than that reported in other hosts.

Faunistic analysis of sharpshooters (Hemiptera: Auchenorrhyncha, Cicadellidae) in a 'Westin' sweet orange orchard

The purpose of this study was to analyze sharpshooter fauna in a five-year-old 'Westin' sweet orange orchard. Yellow sticky traps were placed on the edge of a forest, and on the periphery and inside the citrus stand. The traps were evaluated fortnightly, for three years. The most frequent species were Acrogonia citrina Marucci & Cavichioli, Bucephalogonia xanthophis (Berg), and Oncometopia facialis (Signoret). B. xanthophis occurred more in the forest edge, especially on spring and winter. A. citrina occurred most frequently in the forest edge, especially on spring. The highest incidence of O. facialis was inside the citrus stand, on spring and summer. Other cicadellids occurred more often in the forest edge, especially on summer. A. citrina, B. xanthophis, Dilobopterus costalimai Young, and O. facialis were predominant in all places studied. A. citrina, B. xanthophis and O. facialis were super dominant, super abundant, super frequent, and constant, except inside the stand, where B. xanthophis was dominant, very abundant, very frequent, and constant. D. costalimai and Homalodisca ignorata Melichar were dominant, very abundant, and very frequent in the forest edge and in the periphery of the stand, and D. costalimai was also predominant inside the stand. Scopogonalia subolivacea (Stål) was predominant in the forest edge and inside the stand, while Plesiommata corniculata Young was predominant in the periphery (both were dominant, very abundant, very frequent, and accessory).

Insetos associados à cultura da aceroleira (<em>Malpighia glabra</em> L.) na região de Maringá, Estado do Paraná

Com o objetivo de determinar a ocorrência de insetos associados à aceroleira, Malpighia glabra L. (Malpighiaceae), foram feitos levantamentos, no período de agosto de 1997 a dezembro de 1998, na região de Maringá, Estado do Paraná, Brasil. Os insetos foram coletados quinzenalmente em 20 plantas localizadas em pomar comercial, caminhando-se ao redor da copa das plantas por um período de 10 minutos e observando-se ramos, folhas e frutos. A coleta foi realizada manualmente, através de rede entomológica, armadilha com atraente alimentar e pelo corte de quatro ramos por planta, que foram observados sob microscópio estereoscópico. As espécies encontradas foram; Nezara viridula, Piezodorus guildinii, Euschistus heros, Thyanta spp., Dysdercus ruficolis, D. peruvianus, Leptoglossus zonatus, L. gonagra, Enchenopa gracilis, Toxoptera citricidus, Saissetia coffeae, S. oleae, Coccus viridis, Chrysomphalus ficus, Selenaspidus articulatus, Orthezia praelonga, Mahanarva fimbriolata, M. posticata, Dilobopterus costalimai, Oncometopia facialis, Chrysopa sp., Polistes sp., Diabrotica speciosa, Cerotoma sp., Lagria villosa, Cycloneda sanguinea, Ceratitis capitata, Anastrepha fraterculus e Euxesta sp

Egg Brochosomes of Proconiini (Hemiptera: Cicadellidae, Cicadellinae) species associated with cultivation of grapevines

Brochosomes production is considered a feature of Cicadellidae, and may represent an outstanding innovation which has played an important role in the development and diversification of this insect group. The objective of this study was to identify the species of Proconiini that produced egg brochosomes associated with grapevines in the Serra Gaúcha region of Brazil. Egg brochosome characteristics and an identification key are also discussed. The specimens were collected using yellow sticky cards in four vineyards (Vitis vinifera L.) from October 2004 to May 2006. Eight species capable of producing egg brochosomes were identified:Acrogonia citrina Marucci & Cavichioli; Homalodisca ignorata Melichar; Molomea consolida Schröder; Molomea lineiceps Young; Molomea personata (Signoret); Oncometopia facialis (Signoret); Oncometopia fusca Melichar; and Tapajosa rubromarginata (Signoret). Egg brochosomes are useful structures to identify Proconiini species in vine.

Bioassay assessment of metarhizium anisopliae (metchnikoff) sorokin (deuteromycota: hyphomycetes) against Oncometopia facialis (signoret) (hemiptera: cicadellidae)

Citrus Variegated Chlorosis (CVC) is an economically important, destructive disease in Brazil and is caused by Xylella fastidiosa and transmitted by sharpshooter insects. In this study, the efficacy of the fungus Metarhizium anisopliae in controlling the sharpshooter Oncometopia facialis was studied by bioassay conditions. In the bioassay, insects were sprayed with a suspension containing 5 X 10(7) conidia mL(-1). Adults captured in the field were treated in groups of 10 in a total of 11 replications per treatment. Significant differences between the natural mortality and the mortality of insects treated with the fungus were observed 6 days after inoculations (P<0.05). These significant differences increased until 10 days after treatment. The fungus caused 87.1% mortality, with the LT50 varying from 5 to 6 days. The LC50 was 1.2 X 10(6) conidia mL(-1), varying from 7.7 X 10(5) to 2 X 10(6) conidia mL(-1). The results showed that the sharpshooter O. facialis was susceptible to the entomopathogenic action of M. anisopliae in controlled condition during bioassay.

Retention Sites for Xylella fastidiosa in Four Sharpshooter Vectors (Hemiptera: Cicadellidae) Analyzed by Scanning Electron Microscopy

Xylella fastidiosa is a xylem-limited bacterium that causes citrus variegated chlorosis (CVC), Pierce's disease of grapevine, and leaf scald of coffee and plum and many other plant species. This pathogen is vectored by sharpshooter leafhoppers (Hemiptera: Cicadellidae: Cicadellinae) and resides in the insect foregut. Scanning electron microscopy was used to determine the retention sites of X. fastidiosa for the most common vector species in Brazilian citrus groves, Acrogonia citrina, Bucephalogonia xanthophis, Dilobopterus costalimai, and Oncometopia facialis. After a 48-h acquisition access period on infected citrus or plum, adult sharpshooters were kept on healthy citrus seedlings for an incubation period of 2 weeks to allow for bacterial multiplication. Then the vector heads were incubated for 24 h in a fixative and transferred into a cryoprotector liquid. Bacterial rod cells exhibiting similar X. fastidiosa morphology were found laterally attached to different regions inside the cibarial pump chamber (longitudinal groove, lateral surface, cibarial diaphragm and apodemal groove) of A. citrina, O. facialis, and D. costalimai, and polarly attached to the precibarium channel of O. facialis. Polymerase chain reactions of vector's heads were positive for the presence of X. fastidiosa. No X. fastidiosa-like cells were detected in B. xanthophis. A different type of rod-shaped bacterium was found on B. xanthophis cibarium chamber and images suggest that the cibarium wall was degraded/digested by these bacteria. Colonization patterns of X. fastidiosa in their vectors are fundamental aspects to be explored toward understanding acquisition, adhesion, and transmission mechanisms for development of X. fastidiosa control strategies.

Bioassay assessment of metarhizium anisopliae (metchnikoff) sorokin (deuteromycota: hyphomycetes) against Oncometopia facialis (signoret) (hemiptera: cicadellidae)

Citrus Variegated Chlorosis (CVC) is an economically important, destructive disease in Brazil and is caused by Xylella fastidiosa and transmitted by sharpshooter insects. In this study, the efficacy of the fungus Metarhizium anisopliae in controlling the sharpshooter Oncometopia facialis was studied by bioassay conditions. In the bioassay, insects were sprayed with a suspension containing 5 X 107 conidia mL-1. Adults captured in the field were treated in groups of 10 in a total of 11 replications per treatment. Significant differences between the natural mortality and the mortality of insects treated with the fungus were observed 6 days after inoculations (P<0.05). These significant differences increased until 10 days after treatment. The fungus caused 87.1% mortality, with the LT50 varying from 5 to 6 days. The LC50 was 1.2 X 106 conidia mL-1, varying from 7.7 X 105 to 2 X 106 conidia mL-1. The results showed that the sharpshooter O. facialis was susceptible to the entomopathogenic action of M. anisopliae in controlled condition during bioassay.

Infectividade natural por Xylella fastidiosa Wells et al. de cicadelíneos (Hemiptera: Cicadellidae) de lavouras cafeeiras do Paraná

Xylella fastidiosa Wells et al., a gram-negative and xylem limited bacterium, causes significative economic on several crops, such as the leaf scorch in coffee. It is transmitted by xylem feeding insects and four sharpshooters species have been reported as vectors of X. fastidiosa in coffee. The objective of this study was to determine the natural infectivity of X. fastidiosa in five species of sharpshooters from coffee trees: Acrogonia citrina Marucci & Cavichioli, Bucephalogonia xanthophis (Berg), Dilobopterus costalimai Young, Oncometopia facialis (Signoret) and Sonesimia grossa (Signoret). Samples were collected from coffee plantations in five counties of the North and Northwest regions of the State of Parana, Brazil, from October 1998 through November 2001. A total of 806 samples containing three to five insects were examined for the presence of X. fastidiosa by using PCR and nested PCR tests. X. fastidiosa was present in samples of all five species of sharpshooters collected in the two coffee regions. The average level of natural infectivity potential was 30.4%. However, this natural infectivity ranged from 2.2% for O. facialis to 68.8% for A. citrina. Sharpshooters collected in the spring tended to have lower natural infectivity of X. fastidiosa as compared to those collected in other seasons. The results obtained showed the high potential of dissemination of X. fastidiosa by different insect vectors in coffee trees in Parana.

Ingestão de seiva do xilema de laranjeiras 'Pêra' e 'Valência' (Citrus sinensis (L.) Osbeck) sadias e infectadas por Xylella fastidiosa, pelas cigarrinhas vetoras Oncometopia facialis e Dilobopterus costalimai (Hemiptera: Cicadellidae)

Estudou-se o efeito da infecção pela bactéria Xylella fastidiosa, agente causal da Clorose Variegada dos Citros (CVC), sobre a taxa de ingestão de seiva do xilema de plantas cítricas por duas espécies de cigarrinhas vetoras (Hemiptera: Cicadellidae). Foram utilizados pés-francos de laranjeira-doce (Citrus sinensis) das variedades 'Pêra' e 'Valência', infectadas por X. fastidiosa da linhagem 9a5c, por meio de inoculação mecânica. Os insetos utilizados nos experimentos foram coletados em campo, sendo um representante da Tribo Cicadellini (Dilobopterus costalimai) e um da Proconiini (Oncometopia facialis). A taxa de ingestão de seiva do xilema por O. facialis foi quantificada nos ramos das plantas e a de D. costalimai nas folhas e ramos, por meio da avaliação do volume do líquido (honeydew) excretado por unidade de tempo. O consumo pela cigarrinha O. facialis nas plantas doentes foi menor do que nas plantas sadias. Na variedade 'Pêra' doente, o consumo foi baixo, não permitindo a quantificação da seiva eliminada. Na 'Pêra' sadia e na 'Valência' doente e sadia, O. facialis apresentou valores expressivos de excreção, com maior alimentação no período diurno. Nas plantas sadias das duas variedades, o consumo pela cigarrinha D. costalimai foi maior do que nas plantas com CVC. Comparando-se as variedades, o consumo foi superior na variedade 'Valência', e, em relação às partes da planta, folha e ramo, a taxa de ingestão foi maior no ramo das duas variedades, apresentando consumo maior no período diurno.

Distribuição espacial de Oncometopia facialis (Signoret) (Hemiptera: Cicadellidae) em pomar cítrico

The spatial distribution of Oncometopia facialis (Signoret) was studied in sweet orange to elaborate sampling plans and decision-making procedure for the control of this sharpshooter in the field. The samplings were carried out fortnightly in a grid design disposition of 100 points (plants) in citrus orchard, with yellow sticky traps. The average number of O. facialis ranged from 0.35 to 1.17 insects/trap, with the I index varying from 0.89 to 1.82. The fit tests to negative binomial, Poisson distribution, I index and Morisita index indicated aggregated distribution of this insect. The b result of Taylor's power law was 1.6382 (t = 2.71; d.f. = 11; P < 0.05). Sampling plans were elaborated with a precision level of 10, 20 and 25% of error in the mean estimation.

Influence of Xylella fastidiosa infection of citrus on host selection by leafhopper vectors

AbstractInfection of plants by pathogens can influence their attractiveness and suitability to insect vectors and other herbivores. Here we examined the effects of Citrus sinensis (L.) Osbeck (Rutaceae) infection by the bacterium Xylella fastidiosa, which causes citrus variegated chlorosis (CVC), on the feeding preferences of two sharpshooter vectors, Dilobopterus costalimai Young and Oncometopia facialis (Signoret) (Homoptera: Cicadellidae). Experiments were performed inside observation chambers, in which a healthy plant and an infected one (with or without CVC symptoms) were supplied to a group of 40 sharpshooters. The number of insects that selected each treatment was recorded at several time intervals in 48 h. In another experiment, the ingestion rate on healthy and infected (symptomatic or not) plants was evaluated by measuring the liquid excretion of sharpshooters that were confined on branches of each plant for 72 h. Both sharpshooter species preferred healthy plants to those with CVC symptoms. However, O. facialis did not discriminate between healthy citrus and symptomless infected plants. Feeding by D. costalimai was markedly reduced when confined on CVC‐symptomatic plants, but not on asymptomatic infected ones. The ingestion rate by O. facialis was not affected by the presence of CVC symptoms. The results suggest that citrus trees with early (asymptomatic) infections by X. fastidiosa may be more effective as inoculum sources for CVC spread by insect vectors than those with advanced symptoms.

Brochosomes-for-eggs of the Proconiini (Hemiptera: Cicadellidae, Cicadellinae) species associated with orchards of Citrus sinensis (L.) Osbeck in Rio Grande do Sul, Brazil

Brochosomes are ultramicroscopic reticulate bodies produced by the Malpighian tubules of leafhoppers. Brochosomes are usually either spherical (brochosomes-for-integument) or elongated (brochosomes-for-eggs). In this study, the Proconiini species were diagnosed according to their brochosomes-for-eggs. Brochosome-for-eggs traits and dichotomous key were also discussed. The specimens were collected in nine orchards of Citrus sinensis (Valencia orange), using yellow sticky traps. The orchards are located in seven counties in the state of Rio Grande do Sul: Tenente Portela, Ijuí, Jaguari, Harmonia, Taquari, Montenegro, and Pelotas. Data were collected from October 1999 to December 2000, and from October 2001 to March 2002. Seven species capable of producing brochosomes-for-eggs were identified: Acrogonia citrina Marucci & Cavichioli, Homalodisca ignorata Melichar, Molomea consolida Shröder, Molomea lineiceps Young, Molomea magna (Walker), Oncometopia facialis (Signoret), and Oncometopia fusca Melichar. This study shows that the diversity among brochosomes-for-eggs was a useful tool to identify the Proconiini species.

Zoneamento ecológico de Dilobopterus costalimai Young, Oncometopia facialis Signoret e Acrogonia citrina Marucci &amp; Cavichioli (Hemiptera: Cicadellidae) para Santa Catarina

The goal of this work was to identify the regions of Santa Catarina State, Brazil, with more favorable thermal conditions for the development of Dilobopterus costalimai Young, Oncometopia facialis Signoret and Acrogonia citrina Young Marruci & Cavichioli vectors of the bacterium Xylella fastidiosa Wells, causal agent of the Citrus Variegated Chlorosis (CVC) disease. The West and the Coast regions are the most recommended for citrus growing. However, the ecological zoning was performed for the whole state, because the leafhoppers may transmit the bacterium to others fruit trees, like peach, grapevine and plum. The regions were determined based on thermal requirements of the species. The monthly average temperatures were estimated by the latitude, longitude and altitude data. The estimated values of number of generations varied from 0.9 to 4.5 for D. costalimai and the O. facialis species and of 1.3 to 4.7 for A. citrina. The highest numbers of generations were obtained for the regions of lower altitudes, in areas next to the Uruguay River and also in the Coast region, locations where citrus production is indicated.

Feeding site preference of Dilobopterus costalimai Young and Oncometopia facialis (Signoret) (Hemiptera: Cicadellidae) on citrus plants

The efficiency of Xylella fastidiosa transmission by sharpshooters on citrus plants is low and varies with the vector species. The feeding behavior of the sharpshooter vector related to X. fastidiosa acquisition and inoculation is one of the probable conditioning factors in transmission efficiency. The objective of this study was to assess the behavior of two sharpshooter species, Dilobopterus costalimai Young and Oncometopia facialis (Signoret), in selection of citrus nursery trees and feeding places and to ascertain the influence of sprouting on plant attractiveness to the vectors. Free choice tests were performed with the two species in observation chambers (63 x 63 x 120 cm), releasing 40 individuals per chamber. The number of dead insects were assessed as well as those that chose, or not, one of the treatments, at 3, 15, 21, 24, 39, 45 and 48h after the release. For D. costalimai the leaves were important at the start of host selection, and were substituted over time by the secondary branch. D. costalimai preferred to stay on the secondary leaf nervures followed by the secondary branch. O. facialis showed no difference in preference for staying on the leaves (central and secondary nervures) and secondary branch on citrus plants, and this varied with the time of day. The presence of sprouting in the nursery trees increased the attractiveness of the plant to the two sharpshooter species raising the chances of X. fastidiosa acquisition or inoculation. So, control measures should be adopted against these insects in periods of greater vegetation in orange orchards.

A nested-PCR assay for detection of Xylella fastidiosa in citrus plants and sharpshooter leafhoppers.

Detection of Xylella fastidiosa in citrus plants and insect vectors. Chelex 100 resin matrix was successfully standardized allowing a fast DNA extraction of X. fastidiosa. An amplicon of 500 bp was observed in samples of citrus leaf and citrus xylem extract, with and without symptoms of citrus variegated chlorosis, using PCR with a specific primer set indicating the presence of X. fastidiosa. The addition of insoluble acid-washed polyvinylpyrrolidone (PVPP) prior to DNA extraction of insect samples using Chelex 100 resin together with nested-PCR permitted the detection of X. fastidiosa within sharpshooter heads with great sensitivity. It was possible to detect up to two bacteria per reaction. From 250 sharpshooter samples comprising four species (Dilobopterus costalimai, Oncometopia facialis, Bucephalogonia xanthopis and Acrogonia sp.), 87 individuals showed positive results for X. fastidiosa in a nested-PCR assay. The use of Chelex 100 resin allowed a fast and efficient DNA extraction to be used in the detection of X. fastidiosa in citrus plants and insect vectors by PCR and nested-PCR assays, respectively. The employment of efficient and sensitive methods to detect X. fastidiosa in citrus plants and insect vectors will greatly assist epidemiological studies.