1,721,087 research outputs found
Influence of grapevine water stress on egg laying, egg hatching and nymphal survival of the green leafhopper Empoasca vitis
No full textGrapevine water stress can exert profound effects on the abundance of the green leafhopper Empoasca vitis (Göthe) (Hemiptera: Cicadellidae) in vineyards. Three experiments were carried out using potted grapevines in controlled conditions to investigate the mechanisms involved in this phenomenon. Grapevines were subjected to different levels of water stress, monitored by a pressure chamber, and E. vitis adults were confined on them prior or after the induction of water stress. At the end of each experiment, the number of leafhopper eggs laid in grapevine leaves and that of hatched eggs were counted. Empoasca vitis females preferred to oviposit into leaf veins and petioles, but tendrils and internodes (with a diameter of less than 2 mm) were also used. Moderate water stress levels (stem potential values from –0.9 to –1.0 MPa) reduced the reproductive potential of E. vitis and egg survival (hatching rate of 60%). High stress levels (values from –1.6 to 1.7 MPa) had a marked negative effect on egg laying and egg hatching (hatching rate of 33%), and hence reduced the subsequent abundance of nymphs and adults. Severe stress levels (values from –1.6 to 1.7 MPa) dramatically reduced the survival of eggs (hatching rate of 5%), and subsequently the size of progeny. The positive effect of a moderate water stress on E. vitis control was discussed in relation to yield and grape quality
Influenza delle forme di allevamento della vite sull'abbondanza del cicadellide "Empoasca vitis" (Goethe).
No full textEffects of irrigation on Empoasca vitis populations
No full textThe effect of irrigation on the incidence of pests was investigated in two vineyards located in north-eastern Italy in 2006. Irrigation was performed 2-3 times during the experimental season by a micro-spray system. The leafhopper Empoasca vitis Göthe was the most frequent pest in the two vineyards. Its seasonal abundance was monitored by examining leaf samples. Empoasca vitis population densities were affected by irrigation, and higher levels of this pest were recorded on irrigated vines in particular
Relationships between plant pathogenic fungi and mites in vineyards: implications for IPM
No full textIn this paper we summarize the results of studies aimed at investigating the relationships between fungal diseases and mites occurring in European vineyards. Most of the data originated from observations carried out in commercial and experimental vineyards in north-eastern Italy. Grapevine downy mildew, Plasmopara viticola, and grape powdery mildew, Uncinula necator, are the most significant grape diseases in several viticultural areas in Europe and throughout the world. The spread of downy mildew in European vineyards may increase the abundance of some species of Phytoseiidae and Tydeidae. Amblyseius andersoni responded clearly to the spread of downy mildew symptoms, an effect also observed, but at lower magnitudes, for Typhlodromus pyri and Kampimodromus aberrans. The beneficial effect of downy mildew on the survival, development and reproduction of phytoseiids and tydeids has a clear impact on their population dynamics. Downy mildew effects varied among phytoseiids, being more relevant for A. andersoni than for T. pyri. These interactions may have implications for IPM because T. pyri is more effective than A. andersoni in controlling phytophagous mites in vineyards. The role of powdery mildew as a food source for A. andersoni and T. pyri was less pronounced than that of downy mildew. The capacity of generalist predatory mites to persist in perennial ecosystems contributes to the successful biological control of phytophagous mites. In vineyards, the persistence of generalist predators in the absence of prey may be improved by their feeding on various food sources. Pollen is probably the most important food source in spring and early summer, whereas mildews increase in importance in late summer. Predatory mite persistence is largely affected by pesticide use. The results of our studies showed that downy mildew availability mediates the effects of fungicides on predatory mites because it represents an alternative food for them. Moreover, downy mildew can enhance the recovery of predatory mite populations after pesticide applications
Effect of exclusion net timing of deployment and color on Halyomorpha halys (Hemiptera: Pentatomidae) infestation in pear and apple orchards
Full text linkThe brown marmorated stink bug, Halyomorpha halys (Stål, 1855) (Hemiptera: Pentatomidae), is an invasive pest species native to East Asia that has become the major pest for many crops, causing serious economic damage. The occurrence of this invasive pest leads to an increase in broad-spectrum insecticides applications, often with limited results in H. halys management. Exclusion netting based on insect-proof nets is considered an environmentally friendly tactic that may potentially reduce H. halys infestation and damage. In a first experiment, during two growing seasons we investigated whether the timing of exclusion netting deployment affected season-long H. halys infestation and impact on apple and pear production. A second experiment considered the effect of netting color. Our results confirm that insect-proof nettings are effective in controlling H. halys infestations in fruit orchards, also observing an effect of timing of netting deployment on H. halys adult infestation, especially in apple orchards. Netting deployment could be delayed until the growing fruit phase on pear orchards, while on apple orchards it should be performed at flower fading phase. Brown marmorated stink bug infestation and damage were also influenced by the netting color, with black nets having higher infestation levels and fruit damage than white ones. Within an integrated pest management framework, early net deployment and the use of clear color nettings should be considered to reduce H. halys infestation and its damage in pome fruit crops
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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