60 results on '"Rodrigo, Krugner"'
Search Results
52. Host specificity of Anagrus epos: a potential biological control agent of Homalodisca vitripennis
- Author
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Rodrigo Krugner, Marshall W. Johnson, Joseph G. Morse, and Russell L. Groves
- Subjects
biology ,Macrosteles ,Animal ecology ,Anagrus epos ,Insect Science ,Botany ,Hymenoptera ,biology.organism_classification ,Agronomy and Crop Science ,Hemiptera ,Phoracantha recurva ,Parasitoid ,Circulifer - Abstract
Anagrus epos Girault (Hymenoptera: Mymaridae) is a candidate for a classical biological control program targeting the glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), in California. Because mass production of GWSS is expensive and labor-intensive, a factitious host that is more economical to produce is desirable to mass produce A. epos for colonization and augmentation efforts. Here, we report the results of host specificity tests and potential rearing techniques for A. epos under laboratory conditions. Females discriminated and oviposited into eggs of seven cicadellid species: H. vitripennis, Circulifer tenellus (Baker), Erythroneura variabilis Beamer, Amblysellus grex (Oman), Graphocephala atropunctata (Signoret), Macrosteles severini Hamilton, and H. liturata Ball, and two cerambycid species: Phoracantha recurva Newman and P. semipunctata (F.). Anagrus epos successfully completed development in the eggs of H. vitripennis, C. tenellus, E. variabilis, A. grex, G. atropunctata, M. severini, and H. liturata. The use of a factitious host and potential nontarget effects of this generalist parasitoid are discussed.
- Published
- 2007
53. Large bugs damage pistachio nuts most severely during midseason
- Author
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P.G. da Silva, Rodrigo Krugner, Kent M. Daane, Robert H. Beede, G.B. Weinberger, Shawn A. Steffan, Glenn Y. Yokota, and Walter J. Bentley
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Integrated pest management ,epicarp lesion ,biology ,Green stink bug ,Calocoris ,General Engineering ,lcsh:S ,flat green stink bug ,pistachio ,large bug ,biology.organism_classification ,lcsh:S1-972 ,Fruit set ,lcsh:Agriculture ,Horticulture ,Botany ,kernel necrosis ,leaffooted bug ,lcsh:Agriculture (General) ,Pistachio Nuts ,redshouldered stink bug ,Pest Management - Abstract
“Large bug” damage to pistachio nuts varies by season, as well as among insect species and development stages, with larger bugs typically causing more damage than smaller bugs. We investigated pistachio damage by three large bug species (leaffooted bug, redshouldered stink bug and flat green stink bug) at different development stages and throughout the season, using field surveys and cage studies. Before fruit set occurs in June, most damaged nuts are dropped from the cluster without reducing fruit load. The midseason period (June to July) is the most critical because the damaged nuts remain in the cluster. After shell hardening, the kernel is largely protected from bug feeding.
- Published
- 2005
54. Biology ofMacrocentrus iridescens(Hymenoptera: Braconidae): A Parasitoid of the Obliquebanded Leafroller (Lepidoptera: Tortricidae)
- Author
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Kent M. Daane, Andrew B. Lawson, Glenn Y. Yokota, and Rodrigo Krugner
- Subjects
Tortricidae ,Ecology ,biology ,fungi ,Choristoneura rosaceana ,Polyembryony ,Zoology ,Hymenoptera ,biology.organism_classification ,Brood ,Parasitoid ,Lepidoptera genitalia ,Insect Science ,Botany ,Braconidae ,Ecology, Evolution, Behavior and Systematics - Abstract
Macrocentrus iridescens French is a polyembryonic parasitoid with a wide host and geographic range in North America. In a survey of California pistachio orchards, M. iridescens was the most common parasitoid species reared from the obliquebanded leafroller, Choristoneura rosaceana Harris. To determine its potential as a biological control agent of the obliquebanded leafroller, we conducted laboratory studies and described M. iridescens immature development. We evaluated adult female longevity, brood size, sex ratio, and host stage preference for oviposition. The parasitoid egg develops polyembryonically. At 26.8°C, larval development required 25–30 d, and pupal development 10–12 d. There was a positive relationship between mandible size and development time, although individual stages could not be determined. Adult females survived on average 15.9, 1.6, and 0.9 d at 25°C when provided with honey and fructose solution, water only, or neither, respectively. Oviposition of fertilized eggs was observ...
- Published
- 2005
55. Infectivity and transmission of Xylellua fastidiosa by Philaenus spumarius (Hemiptera: Aphrophoridae) in Apulia, Italy
- Author
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Maria, Saponari, Giuliana, Loconsole, Daniele, Cornara, Raymond K, Yokomi, Angelo, De Stradis, Donato, Boscia, Domenico, Bosco, Giovanni P, Martelli, Rodrigo, Krugner, and Francesco, Porcelli
- Subjects
Hemiptera ,Italy ,Olea ,Host-Pathogen Interactions ,Animals ,Xylella ,Insect Vectors ,Plant Diseases - Abstract
Discovery of Xylella fastidiosa from olive trees with "Olive quick decline syndrome" in October 2013 on the west coast of the Salento Peninsula prompted an immediate search for insect vectors of the bacterium. The dominant xylem-fluid feeding hemipteran collected in olive orchards during a 3-mo survey was the meadow spittlebug, Philaenus spumarius (L.) (Hemiptera: Aphrophoridae). Adult P. spumarius, collected in November 2013 from ground vegetation in X. fastidiosa-infected olive orchards, were 67% (40 out of 60) positive for X. fastidiosa by polymerase chain reaction (PCR) assays. Euscelis lineolatus Brullé were also collected but tested negative for the pathogen. Transmission tests with P. spumarius collected from the Salento area were, therefore, conducted. After a 96-h inoculation access period with 8 to 10 insects per plant and a 30-d incubation period, PCR results showed P. spumarius transmitted X. fastidiosa to two of five periwinkle plants but not to the seven olive plants. Sequences of PCR products from infected periwinkle were identical with those from X. fastidiosa-infected field trees. These data showed P. spumarius as a vector of X. fastidiosa strain infecting olives trees in the Salento Peninsula, Italy.
- Published
- 2014
56. Plant water stress effects on stylet probing behaviors of Homalodisca vitripennis (Hemiptera: Cicadellidae) associated with acquisition and inoculation of the bacterium Xylella fastidiosa
- Author
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Rodrigo, Krugner and Elaine A, Backus
- Subjects
Crops, Agricultural ,Hemiptera ,Plant Stems ,Stress, Physiological ,Acclimatization ,Animals ,Water ,Herbivory ,Xylella ,Insect Vectors ,Plant Diseases - Abstract
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 ofH. 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.
- Published
- 2014
57. Plant water stress effects on the net dispersal rate of the insect vector Homalodisca vitripennis (Hemiptera: Cicadellidae) and movement of its egg parasitoid, Gonatocerus ashmeadi (Hymenoptera: Mymaridae)
- Author
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Rodrigo, Krugner, James R, Hagler, Russell L, Groves, Mark S, Sisterson, Joseph G, Morse, and Marshall W, Johnson
- Subjects
Male ,Citrus ,Dehydration ,Water ,Xylella ,Hymenoptera ,Host-Parasite Interactions ,Insect Vectors ,Hemiptera ,Sex Factors ,Stress, Physiological ,Animals ,Female ,Animal Distribution ,Ovum - Abstract
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 (ET(c)), 80, and 60% ET(c). 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% ET(c) were the least preferred by H. vitripennis. Among all protein-marked individuals captured in the 60% ET(c) 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% ET(c) 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.
- Published
- 2013
58. Estimation of feeding threshold for Homalodisca vitripennis (Hemiptera: Cicadellidae) and its application to prediction of overwintering mortality
- Author
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Youngsoo, Son, Russell L, Groves, Kent M, Daane, David J W, Morgan, Rodrigo, Krugner, and Marshall W, Johnson
- Subjects
Hemiptera ,Male ,Temperature ,Animals ,Female ,Feeding Behavior ,Models, Biological - Abstract
The glassy-winged sharpshooter, Homalodisca vitripennis (Germar), vectors the bacterium Xylella fastidiosa that induces Pierce's disease of grape. This study determined the effect of temperature on the feeding activity of H. vitripennis adults and the resulting production of excreta. The Logan type I model described a nonlinear pattern that showed excreta production increased up to an optimal temperature (33.1°C), followed by an abrupt decline near an estimated upper threshold (36.4°C). A temperature threshold for feeding, at or below which adults cease feeding, was estimated to be 10°C using a linear regression model based on the percentage of adults producing excreta over a range of constant temperatures. A simulated winter-temperature experiment using fluctuating thermal cycles confirmed that a time period above the temperature threshold for feeding was a critical factor in determining adult survival. Using data from the simulated temperature study, a predictive model was constructed by quantifying the relationship between cumulative mortality and cooling degree-hours. In field validation experiments, the model accurately predicted the temporal pattern of overwintering mortality of H. vitripennis adults held under winter temperatures simulating conditions in Bakersfield and Riverside, California, in 2006-2007. Model prediction using winter temperature data from a Riverside weather station indicated that H. vitripennis adults would experience an average of 92% overwintering mortality before reproduction in the spring, but levels of mortality varied depending on winter temperatures. The potential for temperature-based indices to predict temporal and spatial dynamics of H. vitripennis overwintering is discussed.
- Published
- 2011
59. Seasonal population dynamics of Homalodisca vitripennis (Hemiptera: Cicadellidae) in sweet orange trees maintained under continuous deficit irrigation
- Author
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Joseph G. Morse, Russell L. Groves, James Hagler, Marshall W. Johnson, Arnel P. Flores, and Rodrigo Krugner
- Subjects
Canopy ,Irrigation ,Deficit irrigation ,Population ,Population Dynamics ,Fresh Water ,Population density ,California ,Hemiptera ,Botany ,Animals ,Cultivar ,education ,education.field_of_study ,Ecology ,biology ,Temperature ,Agriculture ,General Medicine ,biology.organism_classification ,Glassy-winged sharpshooter ,Horticulture ,Insect Science ,Seasons ,Citrus × sinensis ,Citrus sinensis - Abstract
A 2-yr study was conducted in a citrus orchard (Citrus sinensis L. Osbeck cultivar Valencia) to determine the influence of plant water stress on the population dynamics of glassy-winged sharpshooter, Homalodisca vitripennis (Germar). Experimental treatments included irrigation at 100% of the crop evapotranspiration rate (ET(c)) and continuous deficit-irrigation regimens at 80 and 60% ET(c). Microclimate and plant conditions monitored included temperature and humidity in the tree canopy, leaf surface temperature, water potential, and fruit quality and yield. Glassy-winged sharpshooter population densities and activity were monitored weekly by a combination of visual inspections, beat net sampling, and trapping. Glassy-winged sharpshooter populations were negatively affected by severe plant water stress; however, population densities were not linearly related to decreasing water availability in plants. Citrus trees irrigated at 60% ET(c) had significantly warmer leaves, lower xylem water potential, and consequently hosted fewer glassy-winged sharpshooter eggs, nymphs, and adults than trees irrigated at 80% ET(c). Citrus trees irrigated at 100% ET(c) hosted similar numbers of glassy-winged sharpshooter stages as trees irrigated at 60% ET(c) and a lower number of glassy-winged sharpshooter nymphs than the 80% ET(c) treatment, specifically during the nymphal density peak in mid-April to early July. Irrigation treatments did not affect populations of monitored natural enemies. Although the adult glassy-winged sharpshooter population was reduced, on average, by 50% in trees under severe water stress, the total number of fruit and number of fruit across several fruit grade categories were significantly lower in the 60% ET(c) than in the 80 and 100% ET(c) irrigation treatments.
- Published
- 2009
60. A new Phytoreovirus infecting the glassy-winged sharpshooter (Homalodisca vitripennis)
- Author
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Rodrigo Krugner, Drake C. Stenger, Elaine A. Backus, Wayne B. Hunter, and Mark S. Sisterson
- Subjects
Inverted repeat ,Reoviridae ,Insect Viruses ,Phytoreovirus ,dsRNA ,Genome, Viral ,Hemiptera ,Virology ,Plant virus ,Animals ,Complete genome sequence ,Phylogeny ,RNA, Double-Stranded ,biology ,Sequence Analysis, RNA ,RNA-Dependent RNA Polymerase ,biology.organism_classification ,Sharpshooter (insect) ,Glassy-winged sharpshooter ,Rice dwarf virus ,Nucleic acid ,RNA, Viral ,Capsid Proteins ,Sequence Alignment - Abstract
A new virus species of the genus Phytoreovirus was isolated from glassy-winged sharpshooter (GWSS), Homalodisca vitripennis Germar (Hemiptera: Cicadellidae), in California and designated here as Homalodisca vitripennis reovirus (HoVRV). Extraction of nucleic acid from GWSS adults collected from three Californian populations revealed an array of double-stranded (ds) RNA species that was soluble in 2 M LiCl and resistant to degradation upon exposure to S1 nuclease and DNase. Analysis of nucleic acid samples from single GWSS adults indicated that HoVRV dsRNA accumulated to high titer in individual insects. Double-shelled isometric virus particles purified from GWSS adults resembled those observed in thin sections of GWSS salivary glands by transmission electron microscopy. Purified HoVRV virions contained 12 dsRNA segments that, based on complete nucleotide sequences, ranged in size from 4475 to 1040 bp. Sequence comparisons indicated that the HoVRV dsRNA segments were most closely related (58.5 to 43.7% nt sequence identity) to the corresponding genome segments of Rice dwarf virus (RDV). Each HoVRV dsRNA segment encoded a single open reading frame (>300 nts) except for segment 11, which appears to be dicistronic. Terminal nucleotide sequences of HoVRV positive-sense RNAs were similar to other phytoreoviruses (GGCG or GGCA at the 5′-end and UGAU or CGAU at the 3′-end) with adjacent imperfect inverted repeats potentially able to base pair. Phylogenetic analyses of the RNA-directed RNA polymerase (encoded by segment 1) and the outer capsid protein (encoded by segment 8) confirmed placement of HoVRV as a species of the genus Phytoreovirus sharing a most recent common ancestor with RDV. Reverse transcription-polymerase chain reaction assays revealed that HoVRV infection of GWSS in California was common and that the virus also occurred in GWSS populations from the Carolinas and Texas.
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