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The General Beale Pilot Project serves as a case study for the use of areawide monitoring and treatment programs for glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar), and monitoring and roguing programs for grapevines infected with Xylella fastidiosa, to achieve regional management of Pierce's disease. The Project is located in southeast Kern County, CA, and contains ~2,800 ha of citrus and grapevines grown within approximately 50 km2. For nearly 20 yr, an average of 470 traps have been used to monitor GWSS populations regionally by the California Department of Food and Agriculture, and to inform coordinated, areawide treatments by the USDA-APHIS Areawide Treatment Program to overwintering GWSS in citrus. Grape growers were responsible for treating their own vineyards, and for the roguing of infected grapevines based on surveys provided by the University of California. Herein, we provide a history of the General Beale Pilot Project, broken down into six eras based on levels of Project success, which incorporate data on GWSS captures, pesticide use, and disease incidence. We describe patterns of success related to the regional coordination of effective treatment and roguing programs that can be used by grape and neighboring citrus growers for areawide management of Pierce's disease. We conclude by describing current and future challenges for Pierce's disease management, including pesticide availability and resistance, GWSS refuges, the inability to detect and rogue infected vines in the year they become infected, and the sustainability of voluntary programs that rely on public funding. [ABSTRACT FROM AUTHOR]

Pest management for the glassy-winged sharpshooter, Homalodisca vitripennis Germar (Hemiptera: Cicadellidae), in Kern County, California relies on the application of insecticides. These treatments have contributed to low H. vitripennis field counts since applications were initiated in 2001. However, densities have been high in recent years despite continued management, prompting efforts to evaluate the susceptibility of current populations to insecticides. H. vitripennis adults were subjected to bioassays with five commonly applied insecticides, and the results were compared to baseline toxicities determined in 2002. Two neonicotinoids, imidacloprid and thiamethoxam, were evaluated using systemic uptake bioassays. Contact toxicities of the neonicotinoid acetamiprid and pyrethroids bifenthrin and fenpropathrin were estimated using leaf dip bioassays. Dose-mortality responses were analyzed by probit analysis. For each compound, there was no significant difference in annual LC50 values determined over 2 yr. Compared to baseline toxicities, acetamiprid and bifenthrin were found to be significantly less toxic to H. vitripennis. The LC50 values of these two compounds increased sevenfold and 152-fold, respectively. Tests with the neonicotinoids revealed a trend of decreasing susceptibility levels within each season followed by reversion back to early season LC50 estimates in the following year. In addition, data showed seasonal and site variation in susceptibility to imidacloprid, possibly due to differential applications in nearby fields. [ABSTRACT FROM AUTHOR]

The glassy-winged sharpshooter is an invasive insect capable of transmitting the bacterial pathogen Xylella fastidiosa. Pre-oviposition periods of laboratory-reared glassy-winged sharpshooters are variable. Here, two questions were addressed: does nymphal diet affect pre-oviposition period and how do allocation patterns of resources differ for females that produce eggs versus females that do not? Nymphs were reared on one of three host plant species: cowpea, sunflower, or sorghum. Half of the females were sacrificed at emergence. The remaining adult females were held on cowpea, a host plant species known to support egg maturation via adult feeding. Females were sacrificed on the day of first oviposition or after 9 wk if no eggs were deposited. Females reared as nymphs on sorghum had longer development times and were smaller (head capsule width and hind tibia length) than females reared as nymphs on cowpea and sunflower. However, nymphal diet did not affect percentage of dry weight that was lipid at emergence. Further, nymphal diet did not affect time to deposition of the first egg mass or total number of eggs matured at the time of first oviposition. Egg production reduced the allocation of resources to insect bodies, with body lipid content decreasing with increasing egg production. In general, females increased wet weight 1.4-fold during the first week after adult emergence, with wet weights plateauing over the remaining 9 wk that adults were monitored. Thus, it seems reasonable to hypothesize that resources required for egg production were acquired via adult feeding during the first week after adult emergence. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Glassy‐winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) is an important vector of the bacterium Xylella fastidiosa, the causal agent of Pierce's disease of grapevine. Area‐wide insecticide applications have suppressed GWSS populations for ∼ 25 years, but reduced levels of insecticide susceptibility have been reported. Therefore, alternative methods of control are needed. Objectives of this study were to evaluate the efficacy of playback of vibrational mating communication signals for disrupting mating of GWSS in a natural vineyard setting and to evaluate spectral properties of signal transmission through vineyard trellis. RESULTS: Playback reduced mating of GWSS on grapevines. A total of 28 (of 134) male–female pairs mated in the control treatment (silence) and only one (of 134) pair mated when treated with the vibrational signal playback. Playback of vibrational signals through vineyard trellis was affected by distance from the signal source, with frequency composition being the highest at the source and lowest on vines positioned away from the source. Frequency composition in canes housing test insects decreased exponentially as distance from the source increased, whereas the relative amplitude of analyzed frequencies decreased linearly. CONCLUSION: Although further studies are needed prior to method implementation, data from this study continue to support integration of vibrational mating disruption with current methods to suppress GWSS populations. Published 2018. This article is a U.S. Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

The glassy-winged sharpshooter is an invasive insect capable of transmitting the plant pathogen Xylella fastidiosa. As rates of pathogen spread are a function of vector abundance, identification of factors contributing to glassywinged sharpshooter egg production will aid in predicting population growth. Here, effects of stored energy reserves and adult diet on glassy-winged sharpshooter egg maturation were evaluated. To estimate energy reserves available to adult females at the beginning of feeding assays, residuals from a regression of wet weight on size were used. Analysis of a subset of females sacrificed at the beginning of feeding assays, demonstrated that females with a positive residual wet weight had higher lipid content and carried more eggs than females with a negative residual wet weight. To evaluate effects of diet and energy reserves on egg maturation, energy reserves available to females entering feeding assays on cowpea and grapevine were estimated. For females held on cowpea, residual wet weight and quantity of excreta produced over a 6-d feeding period affected egg production. In contrast, for females held on grapevine, only residual wet weight affected egg production. Comparison of cowpea and grapevine xylem sap determined that eight amino acids were more concentrated in xylem sap from cowpea than from grapevine. Collectively, the results suggest that glassy-winged sharpshooter population growth within crop monocultures will not depend solely on the nutritional quality of the specific crop for producing mature eggs but also on the quantity of energy reserves accumulated by females prior to entering that crop habitat. [ABSTRACT FROM AUTHOR]

BACKGROUND The glassy-winged sharpshooter (GWSS), Homalodisca vitripennis, is an important pest of grapevines due to its ability to transmit Xylella fastidiosa, the causal agent of Pierce's disease. GWSS mating communication is based on vibrational signals; therefore, vibrational mating disruption could be an alternative to insecticides for suppression of the GWSS population. Our objectives were to identify spectral features of the female signal that elicit male signaling, design disruptive signals able to alter male perception and acceptance of a female, and determine the signal intensity required for future field applications. RESULTS Male responses to playback of modified female signals were significantly reduced by 60-75% when part of the female signal spectral components above or below 400 Hz were deleted. Playback bioassays showed that transmission of an 80 Hz pure frequency tone to plants completely suppressed male signaling to female signal playback, even if the disruptive signal amplitude was 10 dB lower than the female signal playback. CONCLUSION Although the mechanism underlying cessation of male signaling activity in the presence of disruption is not yet understood, results suggest that an 80 Hz vibrational signal should be tested in laboratory and field experiments to assess its efficacy in disrupting mating of GWSS. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The agricultural pest known as the glassy-winged sharpshooter (GWSS) or Homalodisca vitripennis (Hemiptera: Cicadellidae) harbors two bacterial symbionts, "Candidatus Sulcia muelleri" and "Ca. Baumannia cicadellinicola," which provide the 10 essential amino acids (EAAs) that are limited in the host plant-sap diet. Although they differ in origin and symbiotic age, both bacteria have experienced extensive genome degradation resulting from their ancient restriction to specialized host organs (bacteriomes) that provide cellular support and ensure vertical transmission. GWSS bacteriomes are of different origins and distinctly colored red and yellow. While Sulcia occupies the yellow bacteriome, Baumannia inhabits both. Aside from genomic predictions, little is currently known about the cellular functions of these bacterial symbionts, particularly whether Baumannia in different bacteriomes perform different roles in the symbiosis. To address these questions, we conducted a replicated, strand-specific RNA-seq experiment to assay global gene expression patterns in Sulcia and Baumannia. Despite differences in genomic capabilities, the symbionts exhibit similar profiles of their most highly expressed genes, including those involved in nutrition synthesis and protein stability (chaperonins dnaK and groESL) that likely aid impaired proteins. Baumannia populations in separate bacteriomes differentially express genes enriched in essential nutrient synthesis, including EAAs (histidine and methionine) and B vitamins (biotin and thiamine). Patterns of differential gene expression further reveal complexity in methionine synthesis. Baumannia's capability to differentially express genes is unusual, as ancient symbionts lose the capability to independently regulate transcription. Combined with previous microscopy, our results suggest that the GWSS may rely on distinct Baumannia populations for essential nutrition and vertical transmission. [ABSTRACT FROM AUTHOR]

Animal communication is a complex behavior that is influenced by abiotic and biotic factors of the environment. Glassy-winged sharpshooters ( GWSS), Homalodisca vitripennis ( Germar) ( Hemiptera: Cicadellidae), primarily use vibrational signaling for courtship communication. Because GWSS is a major pest, transmitting the plant pathogenic bacterium Xylella fastidiosa Wells et al., interruption of communication is a possible avenue for control. Playback of white noise, pre-recorded female signals, and artificial female noise (continuously overlapping female signals) significantly reduced mating of GWSS when compared to silent control mating trials. Furthermore, to begin to determine the mechanism underlying playback control, female signaling activity was recorded in the presence of stimuli. In response to playback of female signals, females signaled (duet-like) more often than females tested in the absence of playback. After the first playback, almost two-thirds of females signaled a response within 3 s. Additionally, one-third of the females signaled within 1 s after cessation of white noise, and significantly more in the time periods following noise termination. Results highlight how GWSS responds to differing competitive disturbances in the environment and lays important ground work that possibly could be used to develop pesticide-free control methods. [ABSTRACT FROM AUTHOR]

The glassy-winged sharpshooter (GWSS), Homalodisca vitripennis, is an important vector of Xylella fastidiosa, the causal agent of Pierce's disease of grapevine. GWSS control relies mainly on insecticides; therefore, an alternative method, such as vibrational mating disruption, is required. However, knowledge of GWSS intraspecific communication is necessary to evaluate applicability of such methods. Mating behavior and associated vibrational signals were described in different social contexts: individuals, pairs, and one female with two competing males. Behavioral analysis showed that GWSS mating communication involved the emission of three male and two female signals, with specific roles in two distinct phases of mating behavior, identification and courtship. Mating success depended on vibrational duets between genders, which were temporarily interrupted in the presence of male rivalry. Male rivalry behavior involved the emission of three distinct rivalry signals. Two rivalry signals resemble female signals and were associated with replacement of the female in the duet by the rival male. The third rivalry signal was emitted by competing males. Data suggested that rival males used mimicry and hostile signals to interrupt the ongoing duet and gain access to a female. In the future, knowledge acquired from this study will be essential to develop a mechanical mating disruption method for GWSS control. [ABSTRACT FROM AUTHOR]

The glassy-winged sharpshooter (Homalodisca vitripennis) is an invasive pest organism, which is found throughout Central America and has recently invaded a few countries in the Pacific Islands. As a carrier of the highly virulent plant pathogenic bacterium Xylella fastidiosa, it is of great economic significance to horticulture and is estimated to cost Californian vineyards over US$100 million per year in control and losses. New Zealand is currently free from this pest, but its recent spread through the Pacific has raised concerns of it establishing in New Zealand, potentially as a result of introduction through human travel. We report here a real-time polymerase chain reaction assay for the rapid identification of H. vitripennis. The assay was extensively validated in silico then optimized and tested against a range of Cicadellidae species, both internationally collected and local to New Zealand. This assay was able to correctly identify H. vitripennis samples, and distinguish between H. vitripennis and close relatives, such as the smoke-tree sharpshooter (Homalodisca liturata) and will be of great benefit to New Zealand biosecurity. [ABSTRACT FROM AUTHOR]

Glassy-winged sharpshooters must feed as adults to produce mature eggs. Cowpea and sunflower are both readily accepted by the glassy-winged sharpshooter for feeding, but egg production on sunflower was reported to be lower than egg production on cowpea. To better understand the role of adult diet in egg production, effects of xylem-sap chemistry on glassy-winged sharpshooter egg maturation was compared for females confined to cowpea and sunflower. Females confined to cowpea consumed more xylem-sap than females held on sunflower. In response, females held on cowpea produced more eggs, had heavier bodies, and greater lipid content than females held on sunflower. Analysis of cowpea and sunflower xylem-sap found that 17 of 19 amino acids were more concentrated in cowpea xylem-sap than in sunflower xylem-sap. Thus, decreased consumption of sunflower xylem-sap was likely owing to perceived lower quality, with decreased egg production owing to a combination of decreased feeding and lower return per unit volume of xylem-sap consumed. Examination of pairwise correlation coefficients among amino acids indicated that concentrations of several amino acids within a plant species were correlated. Principal component analyses identified latent variables describing amino acid composition of xylem-sap. For females held on cowpea, egg maturation was affected by test date, volume of excreta produced, and principal components describing amino acid composition of xylemsap. Principal component analyses aided in identifying amino acids that were positively or negatively associated with egg production, although determining causality with respect to key nutritional requirements for glassy-winged sharpshooter egg production will require additional testing. [ABSTRACT FROM AUTHOR]

The bacterium Xylella fastidiosa is a causal agent of Pierce's disease in grapevines and is considered to be vectored by several xylem-feeding insects. Xylella fastidiosa and its primary insect vector Homalodisca vitripennis are not currently present in New Zealand, but considered a biosecurity threat to the wine industry. Should it be introduced, infection and dispersal of X. fastidiosa within New Zealand vineyards could occur through extant vectors, especially spittlebugs. Electrical Penetration Graph technology was used to compare the feeding behaviour of three spittlebug species (Philaenus spumarius, Carystoterpa fingens and Carystoterpa minor) on grape (Vitis vinifera Sauvignon blanc) and their original host plants. Results suggest that Philaenus spumarius feeds on grape more than the other two spittlebug species. As Philaenus spumarius has been reported as a vector of X. fastidiosa, their potential to transmit the bacterium into grapevines is discussed based on the real feeding times recorded by EPG. [ABSTRACT FROM AUTHOR]

Population structure of Homalodisca coagulata Virus-1 (HoCV-1) among and within field-collected insects sampled from a single point in space and time was examined. Polymorphism in complete consensus sequences among single-insect isolates was dominated by synonymous substitutions. The mutant spectrum of the C2 helicase region within each single-insect isolate was unique and dominated by nonsynonymous singletons. Bootstrapping was used to correct the within-isolate nonsynonymous:synonymous arithmetic ratio (N:S) for RT-PCR error, yielding an N:S value ~one log-unit greater than that of consensus sequences. Probability of all possible single-base substitutions for the C2 region predicted N:S values within 95% confidence limits of the corrected within-isolate N:S when the only constraint imposed was viral polymerase error bias for transitions over transversions. These results indicate that bottlenecks coupled with strong negative/purifying selection drive consensus sequences toward neutral sequence space, and that most polymorphism within single-insect isolates is composed of newly-minted mutations sampled prior to selection. [ABSTRACT FROM AUTHOR]

The glassy-winged sharpshooter, Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), is the primary insect vector of the xylem-limited plant pathogen Xylella fastidiosa fastidiosa Wells (Xanthomonadales: Xanthomonadaceae), the bacterium that causes Pierce's disease of grape, Vitus sp. Because it is mobile and polyphagous, the glassy-winged sharpshooter is key to Pierce's disease outbreaks in California, Florida, and Texas. Adult age structure and X. fastidiosa foregut infectivity rates of glassy-winged sharpshooter from nine Texas vineyards in summer 2007 were assessed from archived samples. The ages of individuals were determined by measuring the red pigmentation of forewing intersections. Presence or absence of X. fastidiosa was determined in the foregut of pathogen-positive insects by quantitative PCR. Larger amounts of the associated pathogen in insects from two vineyards sampled in 2005 and 2006 were observed. No significant differences in average insect age among vineyards or collection dates were found in those years. However, significant differences in average pathogen load among multiple vineyards and collection dates were observed. [ABSTRACT FROM AUTHOR]

The glassy-winged sharpshooter (GWSS) Homalodisca vitripennis (Hemiptera: Cicadellidae), is a xylem-feeding leafhopper and an important vector of the bacterium Xylella fastidiosa; the causal agent of Pierce’s disease of grapevines. MicroRNAs are a class of small RNAs that play an important role in the functional development of various organisms including insects. In H. vitripennis, we identified microRNAs using high-throughput deep sequencing of adults followed by computational and manual annotation. A total of 14 novel microRNAs that are not found in the miRBase were identified from adult H. vitripennis. Conserved microRNAs were also found in our datasets. By comparison to our previously determined transcriptome sequence of H. vitripennis, we identified the potential targets of the microRNAs in the transcriptome. This microRNA profile information not only provides a more nuanced understanding of the biological and physiological mechanisms that govern gene expression in H. vitripennis, but may also lead to the identification of novel mechanisms for biorationally designed management strategies through the use of microRNAs. [ABSTRACT FROM AUTHOR]

Vector control is widely viewed as an integral part of disease management. Yet epidemiological theory suggests that the effectiveness of control programs at limiting pathogen spread depends on a variety of intrinsic and extrinsic aspects of a pathosystem. Moreover, control programs rarely evaluate whether reductions in vector density or activity translate into reduced disease prevalence. In areas of California invaded by the glassy-winged sharpshooter (Homalodisca vitripennis Germar), Pierce's disease management relies heavily on chemical control of this vector, primarily via systemic conventional insecticides (i.e., imidacloprid). But, data are lacking that attribute reduced vector pressure and pathogen spread to sharpshooter control. We surveyed 34 vineyards over successive years to assess the epidemiological value of within-vineyard chemical control. The results showed that imidacloprid reduced vector pressure without clear nontarget effects or secondary pest outbreaks. Effects on disease prevalence were more nuanced. Treatment history over the preceding 5 yr affected disease prevalence, with significantly more diseased vines in untreated compared with regularly or intermittently treated vineyards. Yet, the change in disease prevalence between years was low, with no significant effects of insecticide treatment or vector abundance. Collectively, the results suggest that within-vineyard applications of imidacloprid can reduce pathogen spread, but with benefits that may take multiple seasons to become apparent. The relatively modest effect of vector control on disease prevalence in this system may be attributable in part to the currently low regional sharpshooter population densities stemming from area-wide control, without which the need for within-vineyard vector control would be more pronounced. [ABSTRACT FROM AUTHOR]

Glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar), is a vector of the xylem-inhabitant bacterium Xylella fastidiosa Wells et al., which causes Pierce's disease of grapevines. Current GWSS control strategies in California, USA include area-wide insecticide applications and mass release of mymarid egg parasitoids, including Gonatocerus ashmeadi Girault. Gas chromatography-mass spectrometry was used to identify (E)-β-ocimene and (E,E)-α-farnesene as volatiles emitted from grapevines on which GWSS had previously fed and oviposited. Attractiveness of female G. ashmeadi to sugar-based formulations containing either (E)-β-ocimene, (E,E)-α-farnesene, or a mixture of both was evaluated using Y-tube olfactometry. When exposed to synthetic formulation containing a mixture of (E)-β-ocimene and (E,E)-α-farnesene vs. blank control, 61% of G. ashmeadi females initially chose the synthetic formulation. After the initial choice for a Y-tube arm, females visited the Y-tube arm connected to the source of formulation more often than it did to the arm connected to a blank control. There was no difference in the female's time spent in the arm connected to the formulation. When testing formulations containing either (E)-β-ocimene or (E,E)-α-farnesene alone, there was a 1:1 ratio between the proportion of parasitoid's first choice, visits, and residence time. Results suggest that synthetic formulations containing mixtures of certain plant volatiles may be used to localize GWSS egg parasitoids in vineyard systems. Results are discussed in the context of potential applications in GWSS biological control programs. [ABSTRACT FROM AUTHOR]

In the late 1990s, widespread outbreaks of Pierce's disease in grapevines were linked to transmission via the glassy-winged sharpshooter (GWSS), threatening California's multibillion-dollar table, raisin and wine grape industries. Government agencies responded to the crisis by implementing two control programs to manage GWSS. We analyzed the long-term economic impact of these two programs on citrus, grape and nursery producers. The net economic effects on all citrus producers and on grape producers in the southern San Joaquin Valley were insignificant, while all grape producers in the Temecula Valley saw an average increase in annual production costs of about $13.04 an acre. Based on our survey of nurseries in Southern California, approximately 11% had an infestation in 2008 and 2009, but only 3.0% in 2010. Average losses to nurseries per GWSS infestation were about $12,238. Nursery producers also undertook a variety of pest control methods to prevent infestations and plant losses, and to meet quarantine regulations. Average annual per-acre costs of these approaches were $2,975 for barrier methods to prevent GWSS from entering a premises, $1,032 in pesticide controls and $1,588 for in-house monitoring. [ABSTRACT FROM AUTHOR]

The glassy-winged sharpshooter, Homalodisca vitripennis (Germar) is a significant pest of grapevines in California due to vectoring Xylella fastidiosa Wells et al., Buckwheat (Fagopyrum esculentum Moench) and vetch (Vicia sativa L. cv. 'cahaba white') are potential nectar-producing cover crop plants in California vineyards that could enhance Gonatocerus ashmeadi Girault, a parasitoid of H. vitripennis. Three aspects of these 2 plant species were evaluated. (1) Effect on parasitoid fitness: In the laboratory, buckwheat and vetch enhanced survival of G. ashmeadi by 9 and 6days, respectively, compared to water. G. ashmeadi offspring production was 81% and 142% greater when females were provided vetch or buckwheat, respectively, compared to water. Buckwheat decreased G. ashmeadi female offspring by 19% compared to water and vetch. (2) Nectar production phenology in southern California: From April through September, buckwheat required only 23-32days from sowing to nectar-producing flowers. Vetch required an additional 14-33days to produce extrafloral nectar during June-August. The range in length of the nectar producing period between August 2007 and November 2007 was 41-52days and 163-164days for buckwheat and vetch, respectively. (3) X.fastidiosa Wells et al. host testing and H. vitripennis transmission studies: Needle inoculation of cover crop plants showed that X. fastidiosa successfully infected and replicated in buckwheat, vetch, sweet alyssum [Lobularia maritima (L.) Desv.] and coriander (Coriandrum sativum L.), plants that were assessed here or elsewhere as nectar producing cover crops for use in vineyards. H. vitripennis successfully transmitted X. fastidiosa between buckwheat and grapevine in the greenhouse and field. H. vitripennis successfully transmitted X. fastidiosa from grapevine to vetch in the field, while transmission studies investigating movement from vetch to grapevine in the greenhouse were inconclusive. [ABSTRACT FROM AUTHOR]

The glassy-winged sharpshooter (GWSS) is an invasive insect species that transmits Xylella fastidiosa, the bacterium causing Pierce's disease of grapevine and other leaf scorch diseases. X. fastidiosa has been shown to colonize the anterior foregut (cibarium and precibarium) of sharpshooters, where it may interact with other naturally-occurring bacterial species. To evaluate such interactions, a comprehensive list of bacterial species associated with the sharpshooter cibarium and precibarium is needed. Here, a survey of microbiota associated with the GWSS anterior foregut was conducted. Ninety-six individual GWSS, 24 from each of 4 locations (Bakersfield, CA; Ojai, CA; Quincy, FL; and a laboratory colony), were characterized for bacteria in dissected sharpshooter cibaria and precibaria by amplification and sequencing of a portion of the 16S rRNA gene using Illumina MiSeq technology. An average of approximately 150,000 sequence reads were obtained per insect. The most common genus detected was Wolbachia; sequencing of the Wolbachia ftsZ gene placed this strain in supergroup B, one of two Wolbachia supergroups most commonly associated with arthropods. X. fastidiosa was detected in all 96 individuals examined. By multilocus sequence typing, both X. fastidiosa subspecies fastidiosa and subspecies sandyi were present in GWSS from California and the colony; only subspecies fastidiosa was detected in GWSS from Florida. In addition to Wolbachia and X. fastidiosa, 23 other bacterial genera were detected at or above an average incidence of 0.1%; these included plant-associated microbes (Methylobacterium, Sphingomonas, Agrobacterium, and Ralstonia) and soil- or water-associated microbes (Anoxybacillus, Novosphingobium, Caulobacter, and Luteimonas). Sequences belonging to species of the family Enterobacteriaceae also were detected but it was not possible to assign these to individual genera. Many of these species likely interact with X. fastidiosa in the cibarium and precibarium. [ABSTRACT FROM AUTHOR]

The reproductive and developmental biology, including life tables, for Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), the glassy-winged sharpshooter, were quantified at four constant temperatures in the laboratory: 20, 25, 30, and 33°C. Mean time from egg oviposition to adult death and mean female adult longevity was greatest at 25°C. Mean total progeny production was greatest at 25°C at 214 eggs per individual. The percentage of females ovipositing at each experimental temperature was relatively low at 22, 46, and 56% at 20, 25, and 30°C, respectively. No oviposition occurred at 33°C. Upper, lower, and optimal developmental thresholds were calculated for all life stages, and for egg to adult emergence these were 35.95, 13.99, and 29.45°C, respectively. Key demographic parameters were calculated and intrinsic rate of increase and net reproductive rate were highest at 30 and 25°C at 0.04 and 40.21 d, respectively. Mean generation times and population doubling times were lowest at 25 (97.66 d) and 30°C (15.51 d). Modeling of demographic parameters indicated that approximately three generations of H. vitripennis per year are needed for the existence of permanent populations. Historical weather data were used to map the number of generations and estimate net reproductive rates for H. vitripennis throughout California. Data presented here will be useful for modeling and estimating the possible invasion success of H. vitripennis in areas other than California. [ABSTRACT FROM AUTHOR]

In any insect invasion the presence or absence of suitable food and oviposition hosts in the invaded range is a key factor determining establishment success. The glassy-winged sharpshooter, Homalodisca vitripennis, is an important insect vector of the xylem-limited bacterial plant pathogen, Xylella fastidiosa, which causes disease in numerous host plants including food and feedstock crops, ornamentals and weeds. Both the pathogen and the vector are native to the Americas and are considered to be highly invasive. Neither has been detected in Australia. Twelve Australian native plant species present in the USA were observed over two years for suitability as H. vitripennis feeding, oviposition and nymph development hosts. Hosts providing evidence of adult or nymph presence were Leptospermum laevigatum, Acacia cowleana, Eremophila divaricata, Eucalyptus wandoo, Hakea laurina, Melaleuca laterita and Swainsona galegifolia. An oviposition-suitability field study was conducted with citrus, a favoured oviposition host, as a positive control. Citrus and L. laevigatum, A. cowleana, B. ericifolia×B. spinulosa, C. pulchella, E. divaricata, E. wandoo, H. laurina, and S. galegifolia were found to be oviposition hosts. Egg parasitism by the mymarid parasitoid Gonatocerus ashmeadi was observed on all Australian plants. A number of Australian plants that may facilitate H. vitripennis invasion have been identified and categorised as ‘high risk’ due to their ability to support all three life stages (egg, nymph and adult) of the insect in the field (L. laevigatum, A. cowleana, E. divaricata, H. laurina, and S. galegifolia). The implications of these host status and natural enemy research findings are discussed and placed in an Australian invasion context. [ABSTRACT FROM AUTHOR]

A method to improve an assay relating adult feeding to egg maturation by the glassy-winged sharpshooter (Hemiptera: Cicadellidae) was evaluated. The assay consisted on confining females to cowpea stems and quantifying feeding and egg maturation. Feeding was quantified by measuring excreta production. The number of eggs matured during the assay was estimated by taking the difference between female egg load (number of mature eggs carried by a female) at end of the assay (determined by dissection) and mean egg load of a subset of females dissected at start of the assay. Estimates of the number of mature eggs produced by females using the aforementioned approach improve as variability in egg loads of females entering the assay declines. As egg loads of females are variable, a pretreatment designed to reduce variance in egg loads of females entering the assay was evaluated. To accomplish this, females were divided into two groups. The control group was placed directly into the assay. The pretreatment group was given an oviposition period on sorghum before the assay. An oviposition period on sorghum was expected to reduce variance in egg load among females, as previous research found that sorghum was suitable for oviposition but provided poor nutrition for egg maturation. Dissection of a subset of females from each group before the assay determined that the mean and variance in egg load of females receiving the pretreatment was significantly reduced compared with females in the control group. Analysis of results from the feeding assay found that there was a significant relationship between feeding and egg maturation for females receiving the pretreatment, but not for females in the control group. Thus, reducing the mean and variance in egg load of females entering feeding assays resulted in detection of a significant positive relationship between feeding and egg maturation that otherwise would not have been observed. [ABSTRACT FROM AUTHOR]

The glassy-winged sharpshooter, Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), is a xylem fluid-ingesting leafhopper that transmits Xylella fastidiosa Wells et al., a plant-infecting bacterium that causes several plant diseases in the Americas. Although the role of plant water stress on the population density and dispersal of H. vitripennis has been studied, nothing is known about the effects of plant water stress on the transmission of X. fastidiosa by H. vitripennis. A laboratory study was conducted to determine the influence of plant water stress on the sharpshooter stylet probing behaviors associated with the acquisition and inoculation of X. fastidiosa. Electrical penetration graph was used to monitor H. vitripennis feeding behaviors for 20-h periods on citrus [Citrus sinensis (L.) Osbeck] and almond [Prunus dulcis (Miller) D.A. Webb] plants subjected to levels of water stress. Adult H. vitripennis successfully located xylem vessels, then performed behaviors related to the evaluation of the xylem cell and fluid, and finally ingested xylem fluid from citrus and almond plants under the tested fluid tensions ranging from -5.5 to -33.0 bars and -6.0 to -24.5 bars, respectively. In general, long and frequent feeding events associated with the acquisition and inoculation of X. fastidiosa were observed only in fully irrigated plants (i.e., > -10 bars), which suggests that even low levels of plant water stress may reduce the spread of X. fastidiosa. Results provided insights to disease epidemiology and support the hypothesis that application of regulated deficit irrigation has the potential to reduce the incidence of diseases caused by X. fastidiosa by reducing the number of vectors and by decreasing pathogen transmission efficiency. [ABSTRACT FROM AUTHOR]

Background: The glassy-winged sharpshooter Homalodisca vitripennis (Hemiptera: Cicadellidae), is a xylem-feeding leafhopper and important vector of the bacterium Xylella fastidiosa; the causal agent of Pierce’s disease of grapevines. The functional complexity of the transcriptome of H. vitripennis has not been elucidated thus far. It is a necessary blueprint for an understanding of the development of H. vitripennis and for designing efficient biorational control strategies including those based on RNA interference. Results: Here we elucidate and explore the transcriptome of adult H. vitripennis using high-throughput paired end deep sequencing and de novo assembly. A total of 32,803,656 paired-end reads were obtained with an average transcript length of 624 nucleotides. We assembled 32.9 Mb of the transcriptome of H. vitripennis that spanned across 47,265 loci and 52,708 transcripts. Comparison of our non-redundant database showed that 45% of the deduced proteins of H. vitripennis exhibit identity (e-value ≤1−5) with known proteins. We assigned Gene Ontology (GO) terms, Kyoto Encyclopedia of Genes and Genomes (KEGG) annotations, and potential Pfam domains to each transcript isoform. In order to gain insight into the molecular basis of key regulatory genes of H. vitripennis, we characterized predicted proteins involved in the metabolism of juvenile hormone, and biogenesis of small RNAs (Dicer and Piwi sequences) from the transcriptomic sequences. Analysis of transposable element sequences of H. vitripennis indicated that the genome is less expanded in comparison to many other insects with approximately 1% of the transcriptome carrying transposable elements. Conclusions: Our data significantly enhance the molecular resources available for future study and control of this economically important hemipteran. This transcriptional information not only provides a more nuanced understanding of the underlying biological and physiological mechanisms that govern H. vitripennis, but may also lead to the identification of novel targets for biorationally designed control strategies. [ABSTRACT FROM AUTHOR]

Background: The glassy-winged sharpshooter Homalodisca vitripennis (Hemiptera: Cicadellidae), is a xylem-feeding leafhopper and important vector of the bacterium Xylella fastidiosa; the causal agent of Pierce’s disease of grapevines. The functional complexity of the transcriptome of H. vitripennis has not been elucidated thus far. It is a necessary blueprint for an understanding of the development of H. vitripennis and for designing efficient biorational control strategies including those based on RNA interference. Results: Here we elucidate and explore the transcriptome of adult H. vitripennis using high-throughput paired end deep sequencing and de novo assembly. A total of 32,803,656 paired-end reads were obtained with an average transcript length of 624 nucleotides. We assembled 32.9 Mb of the transcriptome of H. vitripennis that spanned across 47,265 loci and 52,708 transcripts. Comparison of our non-redundant database showed that 45% of the deduced proteins of H. vitripennis exhibit identity (e-value ≤1−5) with known proteins. We assigned Gene Ontology (GO) terms, Kyoto Encyclopedia of Genes and Genomes (KEGG) annotations, and potential Pfam domains to each transcript isoform. In order to gain insight into the molecular basis of key regulatory genes of H. vitripennis, we characterized predicted proteins involved in the metabolism of juvenile hormone, and biogenesis of small RNAs (Dicer and Piwi sequences) from the transcriptomic sequences. Analysis of transposable element sequences of H. vitripennis indicated that the genome is less expanded in comparison to many other insects with approximately 1% of the transcriptome carrying transposable elements. Conclusions: Our data significantly enhance the molecular resources available for future study and control of this economically important hemipteran. This transcriptional information not only provides a more nuanced understanding of the underlying biological and physiological mechanisms that govern H. vitripennis, but may also lead to the identification of novel targets for biorationally designed control strategies. [ABSTRACT FROM AUTHOR]

The pathogenicity of the newly discovered entomopathogenic fungus species Isaria poprawskii, found during epizootics on Bemisia tabaci (Gennadius) in the Lower Rio Grande Valley of Texas, was tested against the glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) Takiya, under laboratory conditions (27 ± 1 °C; 75 ± 5% RH; photoperiod of 14:10 (L:D) h. Exposures of nymphs and adults to 500, 1000, and 2000 conidia/mm2 on cowpea, Vigna unguiculata (L.) Walp, leaves resulted in insect mortality. Median lethal concentrations for second- (685 conidia/mm2) and fourth-instar nymphs (771 conidia/mm2) were similar to those for adults (855 conidia/mm2). Virulence, as measured as mean time to death of the GWSS by survival analysis, was different between concentrations within each insect stage. For example, for the second-instar, I. poprawskii was more virulent at high concentrations (4.6 days) than medium (5.4 days) or low (5.5 days) concentrations. Mycosis in sharpshooters occurred at 3–4 days and continued for 8–10 days after spray. This fungus has the ability to immobilize and stop feeding on infected GWSS, which could potentially slow the spread of Pierce's disease. These results indicate that I. poprawskii is pathogenic to H. vitripennis nymphs and adults. Its pathogenicity and virulence against H. vitripennis show that this fungus is a promising biocontrol agent to control the glassy-winged sharpshooter. [ABSTRACT FROM AUTHOR]

Abstract: Next generation sequence analyses were used to assess virus-derived small RNA (vsRNA) profiles for Homalodisca coagulata virus-1 (HoCV-1), family Dicistroviridae, and Homalodisca vitripennis reovirus (HoVRV), family Reoviridae, from virus-infected H. vitripennis, the glassy-winged sharpshooter. The vsRNA reads were mapped against the monopartite genome of HoCV-1 and all 12 genome segments of HoVRV, and 21nt vsRNAs were most common. However, strikingly contrasting patterns for the HoCV-1 and HoVRV genomic RNAs were observed. The majority of HoCV-1 vsRNAs mapped to the genomic positive-strand RNA and, although minor hotspots were observed, vsRNAs mapped across the entire genomic RNA. In contrast, HoVRV vsRNAs mapped to both positive and negative-sense strands for all genome segments, but different genomic segments showed distinct hotspots. The HoVRV vsRNAs were more common for 5′ and 3′ regions of HoVRV regions of all segments. These data suggest that taxonomically different viruses in the same host offer different targets for RNA-antiviral defense. [Copyright &y& Elsevier]

We examined whether Gonatocerus ashmeadi Girault ( Hymenoptera: Mymaridae), a quasi-gregarious egg parasitoid of Homalodisca vitripennis ( Germar) ( Hemiptera: Cicadellidae), produces precise sex ratios under a field setting. Under laboratory conditions, previous studies have shown that G. ashmeadi exhibits strongly female-biased sex ratios with low variance in the number of males produced per host. Field-collected G. ashmeadi tend to produce much less female-biased sex ratios with high variance in male numbers. We found significant positive effects of proportion parasitism and host density on sex ratio. Proportion parasitism also had a positive effect on sex ratio variance. The findings of this study are discussed in the context of theoretical predictions. [ABSTRACT FROM AUTHOR]

Homalodisca vitripennis (Germar), a vector of Xylella fastidiosa, is associated with citrus plantings in California. Infested citrus orchards act as a source of vectors to adjacent vineyards where X. fastidiosa causes Pierce's disease. An analysis of the pattern and rate of movement of H. vitripennis and its egg parasitoid, Gonatocerus ashmeadi Girault, was conducted in a citrus orchard by using a protein mark-capture technique to quantify movement and net dispersal rates in the experimental areas. Treatments included irrigation at 100% of the crop evapotranspiration rate (ETc), 80, and 60% ETc. Sex-specific net dispersal rates showed that H. vitripennis males and females moved consistently and contributed equally to the level of population change within treated areas. Trees irrigated at 60% ETc were the least preferred by H. vitripennis. Among all protein-marked individuals captured in the 60% ETc treatment, ≈75 and 88% in 2005 and 2006, respectively, were inflow individuals. Movement toward less preferable plants indicates that in agricultural landscapes dominated by perennial monocultures, there is a random component to H. vitripennis movement, which may result from the inability of H. vitripennis to use plant visual cues, olfactory cues, or both to make well-informed long-range decisions. The 80% ETc areas were a significant source of adult H. vitripennis and G. ashmeadi compared with the other treatments. Colonization rates by parasitoids were synchronized with the spatiotemporal distribution of H. vitripennis eggs. Results suggest that H. vitripennis movement from citrus into adjacent vineyards could be a result of random dispersal rather than oriented movement in response to host-plant characteristics. [ABSTRACT FROM AUTHOR]

Pseudoligosita plebeia (Perkins) (Hymenoptera: Trichogrammatidae) is a candidate biological control agent targeting the glassy-winged sharpshooter, Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), in California. Little is known about the biology of P. plebeia. Here we report the results of laboratory studies describing the longevity of P. plebeia adults provided alternative food resources, their ability to parasitize H. vitripennis eggs of different ages, lifetime offspring production when provided steady access to excess host eggs, and levels of mature ovarian eggs present when wasps were held without access to hosts. P. plebeia is a gregarious parasitoid, with up to six adults emerging from a single H. vitripennis egg. When provided with honey and water, water alone, or no food or water, P. plebeia adult females lived an average of 64.1, 2.3, and 2.0 d, respectively. P. plebeia were able to successfully parasitize all ages of H. vitripennis eggs (1-8 d old), with higher parasitism in younger host eggs (1-3 d old) than in older host eggs (5-7 d old). An increasing trend in offspring production was seen for P. plebeia from adult age 2-26 d followed by a decreasing trend with offspring produced up to age 75 d. P. plebeia females are at least partially synovigenic, as they contained fewer mature eggs at younger ages (1 and 3 d old) than at older ages (5, 11,15, and 31 d old). Our results provide foundational information regarding the biology of P. plebeia useful for its further evaluation as a potential biological control agent in California. [ABSTRACT FROM AUTHOR]

Effects of ambient spring air temperature and light intensity on stylet penetration activities of the glassy-winged sharpshooter, Homalodisca vitripennis (Germar), were studied under field conditions by using an electrical penetration graph. Electrical penetration graph waveforms representing salivary sheath formation and searching (pathway phase), xylem contact (X waves), and ingestion of xylem fluid (waveform C) were analyzed. Previous research supported the concept that acquisition of Xylella fastidiosa, the Pierce's disease bacterium, occurs during ingestion, whereas inoculation occurs during xylem contact periods (X waves). Diel patterns of H. vitripennis stylet activity showed that, regardless of light condition, xylem ingestion occurred for the longest duration when temperature remained above the feeding threshold (10°C), and only occurred at temperatures below the threshold when ingestion was continued from a preceding, warmer time. Regression analysis indicated that mean waveform durations per insect (WDI) for combined stylet activities (pathway and ingestion) as well as X wave frequencies were significantly influenced by temperature, but there was no significant impact of light intensity or interaction between temperature and light intensity. The relationship between temperature and stylet activities in terms of WDI and X wave frequency was described using linear and nonlinear models. Validation of the nonlinear models indicated that they well predicted the WDIs for both ingestion and combined stylet activities, using temperature only as a single input. Overall, findings clearly demonstrate that temperature is an important factor that influences the H. vitripennis feeding behaviors responsible for transmission (acquisition and inoculation) of the Pierce's disease bacterium, with implications for vector ecology and management, as well as disease epidemiology. [ABSTRACT FROM AUTHOR]

The glassy-winged sharpshooter, Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), is an important insect vector of the xylem-limited plant pathogen Xylella fastidiosa Wells et al. that causes diseases in numerous plant species including food and feedstock crops, ornamentals and weeds. Both the pathogen and the vector are native to the Americas, and H. vitripennis has demonstrated high invasive ability but to date neither has been detected in Australia. The Australian wine grape, table grape, peach, plum, nectarine and citrus industries are particularly concerned about the arrival of X. fastidiosa and H. vitripennis because of the potential economic impact on these important commodities. Other commodity producers in Australia should also be concerned about this vector-pathogen, in particular the ornamental plant, avocado and olive industries. Past interceptions of H. vitripennis and the potential for X. fastidiosa to be moved in live plant material or within live vectors indicate the need for rapid detection of an incursion in areas considered at high risk. This requires identification of regions that have climatic and environmental conditions conducive to X. fastidiosa and H. vitripennis establishment as well as a detailed knowledge of their respective potential host plant ranges in new areas. These climatic regions and host plant species can then be targeted for monitoring in order to detect an incursion at an early stage. CLIMEX modelling has shown that much of coastal Australia has temperatures suitable for survival of both the vector and pathogen. A range of other requirements in addition to suitable climate must, however, be satisfied for an incursion to lead to establishment, proliferation and spread. This review article provides information that shows that the Australian environment is suitable for the establishment of H. vitripennis and that Australian native plant species are likely to serve as X. fastidiosa hosts and subsequent pathogen sources, and highlights future research directions. [ABSTRACT FROM AUTHOR]

Abstract: A few phytophagous hemipteran species such as the glassy-winged sharpshooter, Homalodisca vitripennis, (Germar), subsist entirely on xylem fluid. Although poorly understood, aspects of the insect’s salivary physiology may facilitate both xylem-feeding and transmission of plant pathogens. Xylella fastidiosa is a xylem-limited bacterium that causes Pierce’s disease of grape and other scorch diseases in many important crops. X. fastidiosa colonizes the anterior foregut (precibarium and cibarium) of H. vitripennis and other xylem-feeding vectors. Bacteria form a dense biofilm anchored in part by an exopolysaccharide (EPS) matrix that is reported to have a β-1,4-glucan backbone. Recently published evidence supports the following, salivation-egestion hypothesis for the inoculation of X. fastidiosa during vector feeding. The insect secretes saliva into the plant and then rapidly takes up a mixture of saliva and plant constituents. During turbulent fluid movements in the precibarium, the bacteria may become mechanically and enzymatically dislodged; the mixture is then egested back out through the stylets into plant cells, possibly including xylem vessels. The present study found that proteins extracted from dissected H. vitripennis salivary glands contain several enzyme activities capable of hydrolyzing glycosidic linkages in polysaccharides such as those found in EPS and plant cell walls, based on current information about the structures of those polysaccharides. One of these enzymes, a β-1,4-endoglucanase (EGase) was enriched in the salivary gland protein extract by subjecting the extract to a few, simple purification steps. The EGase-enriched extract was then used to generate a polyclonal antiserum that was used for immunohistochemical imaging of enzymes in sharpshooter salivary sheaths in grape. Results showed that enzyme-containing gelling saliva is injected into xylem vessels during sharpshooter feeding, in one case being carried by the transpiration stream away from the injection site. Thus, the present study provides support for the salivation-egestion hypothesis. [Copyright &y& Elsevier]

BACKGROUND: The glassy winged sharpshooter, Homalodisca vitripennis, is an unusually robust and efficient leafhopper vector of Xylella fastidiosa. X. fastidiosa is the causative agent of Pierce's disease, almond scorch, citrus variegated chlorosis and other serious plant diseases. The present study was conducted to establish whether RNA interference (RNAi) was induced in nymphal H. vitripennis that were injected with actin dsRNAs and other dsRNAs. RESULTS: A dramatic reduction in target H. vitripennis actin mRNAs and the formation of small interfering RNAs (siRNAs), hallmarks of RNAi, were found following the injection of actin dsRNAs. Quantitative reverse transcription PCR indicated an 80% reduction in actin mRNA levels by 5 days post-injection. Western blot analysis showed a dramatic drop in actin protein levels by 3 days post-injection. Biological effects such as incomplete nymphal-adult ecdysis and > 95% mortality were also found following the injection of fifth-instar nymphs with actin dsRNA. Dramatic reductions in target mRNA levels were also found following the injection of other dsRNAs into fifth-instar H. vitripennis. CONCLUSION: The findings indicate that RNAi is induced in post-embryonic leafhoppers by dsRNA. The present system can be used to screen potential gene-silencing targets that can be used for reducing the vector competence of H. vitripennis and other leafhoppers. Copyright © 2011 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The xylem-limited bacterium Xylella fastidiosa Wells, Raju, Hung, Wiseberg, Mandelico-Paul & Brenner causes bacterial leaf scorch, a new disease of southern highbush blueberry [ Vaccinium corymbosum L. (Ericaceae) interspecific hybrids] in the southeastern USA. The bacterium is transmitted by sharpshooter leafhoppers (Hemiptera: Cicadellidae), with the glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar), being the most common potential vector in blueberry plantings. Considerable differences are observed in disease intensity among blueberry cultivars in the field, but it remains unknown whether these differences are due to variations in cultivar susceptibility to the bacterium, differences in attractiveness to its vector(s), or both. The settling and feeding behavior of GWSS was evaluated on three southern highbush blueberry cultivars (FL 86-19, Star, and Emerald) in the greenhouse; in previous field studies, these cultivars were found to be affected by bacterial leaf scorch at high, moderate, and low levels, respectively. Potted plants were caged together with field-collected GWSS adults for a period of 5 days, with either all three cultivars caged simultaneously (choice test) or individually (no-choice test). In the choice tests, no differences in cultivar attractiveness were observed during the first 2 days of study. However, from the 3rd day, significantly more adults settled on Emerald (52.7%) than on Star (25.5%) and FL 86-19 (17.7%). In contrast, in no-choice tests, the overall host plant acceptance for the three cultivars was similar, and 89.3-92.1% of adults settled on these plants. A significantly greater number of adults settled on the stems (79.3%) vs. the leaves (11.2%). Moreover, they preferred the middle portion of the shoot (56.9%) compared with the upper (7.8%) and the lower (14.7%) portions. In a separate study on FL 86-19, greater numbers of GWSS nymphs settled on the upper (actively growing) portion of the shoot (82.3%), whereas only 15.8 and 1.5% settled on the middle and lower portions, respectively. [ABSTRACT FROM AUTHOR]

Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) is an invasive vector of Xylella fastidiosa, the causal agent of Pierce's disease of grapevines (Vitis vinifera L.). Transmission efficiency of X. fastidiosa to grapevines by H. vitripennis originating from two geographically separated populations in California (Riverside and Bakersfield) based on gender and age was evaluated. To evaluate transmission efficiencies among groups, insects were given a 96-h acquisition access period on infected grapevines and caged in groups of five on healthy grapevines for a 72-h inoculation access period. At the conclusion of tests, polymerase chain reaction determined that a mean ± SD of 0.98 ± 1.02 X. fastidiosa-positive H. vitripennis were present on each grapevine and that 29% of test plants were infected. Acquisition and retention of X. fastidiosa was not affected by vector origin, gender, or age. The probability that a grapevine was infected 12 wk after the inoculation access period increased with the number of X. fastidiosa-positive H. vitripennis per plant. Gender had no effect on inoculation success and main effects of insect origin and age on inoculation success were minor. Collectively, the result indicated that H. vitripennis origin, gender, and age did not affect acquisition and retention of X. fastidiosa and had only minor effects on inoculation success under laboratory conditions. Accordingly, rates of pathogen spread in the field are more likely to be affected by local biotic and abiotic factors that differentially affect H. vitripennis abundance and movement based on origin, gender, and age than inherent differences in transmission efficiencies among these groups. [ABSTRACT FROM PUBLISHER]

Abstract: The effects of temperature on the development (egg–adult emergence) of Gonatocerus morgani Triapitsyn, a newly-described parasitoid of Homalodisca vitripennis (Germar), were determined at 14.8, 18.7, 23.5, 26.9, 28.7, 30.4, 32.8, and 33.8°C in the laboratory. Survival rate (percent adult emergence from parasitized host eggs) varied significantly among the experimental temperatures, with the highest (59%) and lowest (0%) occurring at 30.4 and 33.8°C, respectively. The survival rates (%) were fitted with a polynomial model to describe a temperature-dependent pattern. Developmental rates (1/d) across seven temperatures were fitted with the nonlinear Briere model, which estimated the lower threshold to be 8.06°C, the optimal temperature to be 29.22°C, and the upper threshold to be 33.49°C. A linear model fitted to developmental rates at 14.8–28.7°C indicated that 189.75degree-days above the lower threshold of 9.71°C were required to complete development. A simulation model of G. morgani adult emergence was constructed to predict daily counts over the entire range of constant temperatures by incorporating the survival rate model, the Briere model, and the Weibull model. In outdoor validation, a degree-day model for predicting adult emergence showed ⩽2d differences between prediction and observation. Based on the observed temperature requirement, the insect could complete thirteen to sixteen generations per year in southern California, depending on weather and location. [Copyright &y& Elsevier]

We investigated the distribution and prevalence of egg parasitoids of the glassywinged sharpshooter, Homalodisca vitripennis (Germar 1821), at six field sites over two years. Percentage parasitism often reached 100% from June until October. Most of the observed parasitism was attributed to two species of Gonatocerus, G. ashmeadi Girault 1915 and G. walkerjonesi S. Triapitsyn 2006, with the former producing most of the parasitism in interior southern California and the latter being predominant at coastal sites. This is the first published study that indicates G. walkerjonesi may be dominant in parts of California. Other species detected at low levels were G. novifasciatus Girault 1911, G. morgani S. Triapitsyn 2006, Ufens principalis Owen 2005, and U. ceratus Owen 2005. [ABSTRACT FROM AUTHOR]

The article focuses on a research conducted in order to determine the age of the glassy-winged sharpshooter, Homalodisca vitripennis (H. vitripennis), using wing pigmentation. It discusses the determination of the age of H. vitripennis by calculating the amount of red pigment found in the wings. The study revealed the effects of the environmental conditions on the age determination of H. vitripennis.

The capacity to predict the geographic distribution and relative abundance of invasive species is pivotal to developing policy for eradication or control and management. Commonly used methods fall under the ambit of ecological niche models (ENMs). These methods were reviewed and shortcomings identified. Weather-driven physiologically based demographic models (PBDMs) are proposed that resolve many of the deficiencies of ENMs. The PBDM approach is used to analyze the invasiveness of the polyphagous glassy-winged sharpshooter (Homalodisca vitripennis [Germar] ), a pest native to the southeastern United States and northeastern Mexico that extended its range into California in 1989. Glassy-winged sharpshooter vectors the pathogenic bacterium, Xylella fastidiosa (Wells) that causes Pierce's disease in grape and scorch-like diseases in other plants. PBDMs for glassy-winged sharpshooter and its egg parasitoids (Gonatocerus ashmeadi Girault and G. triguttatus Girault) were developed and linked to a PBDM for grape published by Wermelinger et al. (1991). Daily weather data from 108 locations across California for the period 1995-2006 were used to drive the PBDM system, and GRASS GIS was used to map the simulation results. The geographic distribution of glassy-winged sharpshooter, as observed, is predicted to be largely restricted to the warm areas of southern California, with the action of the two egg parasitoids reducing its abundance >90%. The average indispensable mortality contributed by G. triguttatus is <1%. A temperature-dependent developmental rate model for X. fastidiosa was developed that suggests its geographic range is also limited to the warm inland areas of southern California. Biological control of glassy-winged sharp- shooter further decreases the pathogen's relative range. Climate warming scenarios of + 2°C and +3°C suggest that the distribution and severity of glassy-winged sharpshooter and X. fastidiosa will increase in the agriculturally rich central valley of California. The utility of holistic analyses for formulating control policy and tactics for invasive species is discussed. [ABSTRACT FROM AUTHOR]

The glassy-winged sharpshooter, Homalodisca vitripennis (Germar), is an invasive pest that has spread across the southern and western United States. H. vitripennis is highly polyphagous and voracious, feeding on at least 100 plant species and consuming up to 100 times its weight in xylem fluid daily. The insect is a vector of the phytopathogen Xylella fastidiosa (Wells), which is the causative agent of Pierce's disease in grapevines. To evaluate the microbial flora associated with H. vitripennis, total DNA extracts from hemolymph, alimentary canal excretions, and whole insect bodies were subjected to 16S rDNA pyrosequencing using the bTEFAP methodology and the resulting sequences (370-520 bp in length) were compared with a curated high quality 16S database derived from GenBank (www.ncbi.nlm.nih.gov). Species from the genera Wolbachia, Delftia (formerly Pseudomonas), Pectobacterium, Moraxella, Serratia, Bacillus, and many others were detected and a comprehensive picture of the microbiome associated with H. vitripennis was established. Some of the bacteria identified in this report are initial discoveries; providing a breadth of knowledge to the microbial flora of this insect pest can serve as a reservoir of information for developing biological control strategies. [ABSTRACT FROM AUTHOR]

Abstract: Egg age preference, competitive ability, and behavior of Gonatocerus tuberculifemur (‘new association’ parasitoid) and Gonatocerus ashmeadi (‘old association’ parasitoid) were investigated in the laboratory to determine if one species exhibited competitive superiority. When searching concurrently for Homalodisca vitripennis egg masses, G. ashmeadi consistently outperformed G. tuberculifemur by parasitizing 25–53% more eggs under three different experimental systems in the laboratory with varying host densities, egg ages, and exposure times. G. ashmeadi parasitism in control vials containing one parasitoid ranged from 81–97% across all egg ages. G. tuberculifemur in control vials parasitized 60–66% of eggs 1 and 3days old, and just 18% of eggs 5days old. G. ashmeadi produced 5–16% more female offspring than G. tuberculifemur for all experimental conditions. In comparison to G. ashmeadi, G. tuberculifemur was observed off leaves with host eggs 20% more frequently and it oviposited 15% less frequently. G. ashmeadi and G. tuberculifemur when confined together allocated ∼1% of behaviors to antennating or aggressively chasing competitors off egg masses, and up to 2% of behaviors to antennating host egg masses and/or ovipositing into eggs from the opposite side of the leaf. These latter behaviors did not occur when parasitoids were confined alone with host eggs. [ABSTRACT FROM AUTHOR]

Abstract: The glassy-winged sharpshooter, Homalodisca vitripennis (Germar), is native to the southeastern United States and northeastern Mexico. It was detected in southern California in the late 1980s and in the San Joaquin Valley in 1999, where it transmits the bacterium Xylella fastidiosa to grapevines and other crops. The reproductive success of hybrid and pure line H. vitripennis from two geographically separated populations in California (Riverside (RIV) and Bakersfield (BAK)) was evaluated under identical conditions. The RIV and BAK populations had different preoviposition periods that persisted through the second generation of each lineage. From adult molt, the preoviposition period in both female generations was significantly shorter for RIV (F0 = 28.2 days and F1 = 62.3 days) than BAK females (F0 = 46.1 days and F1 = 170.4 days). After a 21-day mating period, F0 and F1 females deposited on average 391 (range, 21–967) and 196 (range, 0–755) eggs, respectively, without significant differences in fecundity among the F0 and F1 mating pair treatments. Egg accumulation rates among F1 treatments showed that females in the RIV groups rapidly deposited their eggs within the first 120 days after adult molt while BAK females maintained a steady accumulation rate during their life. The performance of both hybrid lines was intermediate between the pure lineages. The F0 mating pairs: ♀RIV × ♂RIV, ♀RIV × ♂BAK, ♀BAK × ♂RIV, and ♀BAK × ♂BAK produced on average 185, 94, 79, and 0 viable eggs, respectively, which suggested a delayed sexual maturity of BAK males and females. The proportion of viable eggs deposited decreased gradually, which suggests that females completely exhausted sperm reserves. From a management perspective, delayed reproductive maturity and polyandry are weak links in H. vitripennis’ biology that may be exploited through mating disruption or insect sterilization strategies to reduce population growth and augment pressure by natural enemies. [Copyright &y& Elsevier]

Abstract: As RNA viruses evolve rapidly, we hypothesized that a virus could serve as a surrogate to discriminate recently separated populations of an invasive insect species. Homalodisca vitripennis reovirus (HoVRV) was used as a surrogate to assess population structure of glassy-winged sharpshooter (GWSS), an invasive species detected in California ~20years ago. HoVRV nucleotide sequence polymorphism revealed a bottleneck in the introduced population, yielded population age estimates consistent with timing of GWSS discovery in California, suggested gene flow within the native range but not among native and introduced populations, and could potentially pinpoint source of the introduced population. Collectively, the data support use of a virus surrogate to define critical attributes of invasive species populations, with the caveat that life history of the surrogate must be closely linked to that of the host. [ABSTRACT FROM AUTHOR]

Abstract: The glassy-winged sharpshooter, Homalodisca vitripennis (Germar), is a serious pest of grapes and other crop and ornamental plants mainly through its role as a vector of the bacterium Xylella fastidiosa Wells. Citrus harbors large populations of this insect throughout much of the year in areas where the pest is problematic and improved understanding of the population dynamics and management of H. vitripennis on citrus may be key to its management in the broader agricultural landscape. In turn, the study of population dynamics and the development of management strategies require effective and efficient sampling methods. Within-tree sampling distribution studies revealed that adults and nymphs were more abundant and less variable in the upper strata of citrus trees (>1.5 m). They occurred in greater numbers on the southern quadrants of trees but relative variability did not differ due to cardinal direction. We developed and validated several fixed-precision sequential sampling plans for estimating the density of nymphs and adults of H. vitripennis using a pole bucket sampling method. Based on validation from resampling of independent data sets, Green’s sequential sampling model, based on the Taylor’s power law, provided the best overall performance in terms of providing mean density estimates with levels of precision equal to or better than the desired precision over a range of possible insect densities. Average sampling costs varied from about 21 to 189 min for a desired precision of 0.25 depending on insect density and whether the goal is to sample nymphs, adults or both stages combined. Further, the sampling plans developed on orange trees were robust, being equally effective on orange and lemon trees and on trees treated or not with insecticides. [Copyright &y& Elsevier]

Development, survivorship, longevity, reproduction, and life table parameters of the glassy-winged sharpshooter, Homalodiscavitripennis (Germar), were examined in the laboratory using three host plants, sunflower (Helianthus annuum L), Chrysanthemum morifolium L., and euonymus (Euonymus japonica Thurb. ). Females deposited similar-sized egg masses on all three plants. Hatching was highest with eggs deposited on euonymus and lowest for those deposited on sunflower. Embryonic development time among host plants was similar while nymph development time was shortest on sunflower and longest on euonymus. Nymph survival to adulthood ranged from 32% on euonymus to 82% for those reared on sunflower. Adult females had similar life spans on sunflower and chrysanthemum. H. vitripennis completed a lengthy egg-to-adult development on euonymus, however, mating did not occur. The onset of mating was contingent on maturation of adult females. The majority of mating activity occurred within the first three days after onset. Premating periods ranged from 6 to 7 d on sunflower to 27 d on chrysanthemum, with overall mating rates of 77.4 and 19.8%, respectively. Females typically mated more than once and they had the longest oviposition period and highest egg production on sunflower; ≈50 and 67% of total number of eggs were deposited within first 45 d after the start of oviposition on sunflower and chrysanthemum, respectively. Adult size and weight related to which host plant was consumed throughout development. Greater intrinsic and finite rates of increase and net reproduction rate, and shorter population doubling time occurred when the sharpshooters were allowed to develop on sunflower. The overall developmental and reproductive parameters obtained in this study indicate that a mixed host plant system, composed of sunflower and euonymus or chrysanthemum plants, is an efficient means for optimizing egg production and colony maintenance of the glassy-winged sharpshooter. [ABSTRACT FROM AUTHOR]

Homalodisca liturata Ball, commonly known as "smoke tree sharpshooter", transmits Xillela fastidiosa Wells bacterium, which causes Pierce's disease and severe damage to many U.S. and Mexican orchards. This is the first observation of variation in host preference among populations of H. liturata in Mexico. Plants preferred by H. liturata were studied during 2007 and 2008 in an experimental field of a community of sarcocaulescent shrub plants in southern Baja California Peninsula. Thirty-one species of plants were associated with the insect, but only 26 where host plants, with a marked preference for Yucca valida Brand. and Prosopis articulate S. Watts, on which greater numbers of insects were found; fewer insects were observed on Lysiloma candida Brand., Cyrtocarpa edulis Brand., and Bursera microphylla A. Gray. Most insects were observed in March and April, and the insect was generally absent in the summer between July and September when temperatures were warmest. Y. valida is a host with potential commercial importance because it contains saponins, but H. liturata should be managed to be able to use Y. valida commercially. [ABSTRACT FROM AUTHOR]

Xylella fastidiosa is a plant pathogenic bacterium that causes many economically important agricultural diseases and is transmitted by the glassy-winged sharpshooter, Homalodisca vitripennis (Hemiptera: Cicadellidae). Efficient detection of X. fastidiosa in field collected H. vitripennis in an area-wide management program can contribute to risk assessment associated with insect presence in vineyards. Prior to conducting molecular assays for detection of X. fastidiosa in individual insects, H. vitripennis must be removed from yellow sticky traps with a solvent such as orange oil. In this study, we determined the effect of orange oil concentration on extraction of individual H. vitripennis following trap removal on detection of X. fastidiosa by qRT-PCR. In a ten-fold dilution series of orange oil, increasing amounts of orange oil caused decreasing levels of X. fastidiosa detection in standardized positive samples. Additionally, tests on the effects of Stickem® brand trap adhesive on qRT-PCR and development of methods which lowered the concentration of orange oil often present in field samples determined the point where detection of X. fastidiosa was negatively impacted. These results benefit the monitoring and screening for Xylella fastidiosa from leafhoppers collected on sticky cards used in regulatory area-wide management. [ABSTRACT FROM AUTHOR]

In laboratory experiments, a flameless catalytic infrared emitter, fueled by propane, was used to disinfest hard red winter wheat, Triticum aestivum L., containing different life stages of the lesser grain borer, Rhyzopertha dominica (F.), an economically important insect species associated with stored wheat in Kansas. The emitter generates infrared radiation in the 3-7-μm range. The life stages of R. dominica exposed to infrared radiation included eggs, larvae in different stages of development, pupae, and 2-wk-old adults. A noncontact infrared thermometer measured grain temperatures continuously during exposures of infested wheat to infrared radiation. The grain temperatures attained were influenced by wheat quantity; distance from the emitter; and exposure time, which in turn influenced effectiveness against various life stages of R. dominica. In general, higher grain temperatures were attained in 113.5 g of wheat as opposed to 227.0 g, and at 8.0 cm from the emitter surface rather than at 12.7 cm, and during a 60-s exposure compared with a 45-s exposure. Logistic regression indicated the probability of death of various life stages of R. dominica was temperature dependent. The log odds ratios showed old larvae were less susceptible to infrared radiation than young larvae. Approximately ≥94% mortality of all R. dominica life stages occurred when using 113.5 g of wheat, exposed for 60 s at a distance of 8.0 cm from the emitter, resulting in mean ± SE wheat temperatures that ranged between 107.6 ± 1.4 and 113.5 ± 0.5°C. Our results with small grain quantities show flameless catalytic infrared technology to be a promising tool for disinfestation of stored wheat. [ABSTRACT FROM AUTHOR]