93 research outputs found
A mathematical model of flavescence dorée epidemiology
No full textFlavescence dorée (FD) is a disease of grapevine transmitted by an insect vector, Scaphoideus titanus Ball.
At present, no prophylaxis exists, so mandatory control procedures (e.g. removal of infected plants, and
insecticidal sprays to avoid transmission) are in place in Italy and other European countries. We propose
a model of the epidemiology of FD by taking into account the different aspects involved into the transmis-
sion process (acquisition of the disease, latency and expression of symptoms, recovery rate, removal and
replacement of infected plants, insecticidal treatments, and the effect of hotbeds). The model was con-
structed as a system of first order nonlinear ODEs in four compartment variables. A bifurcation analysis
shows that, in the absence of hotbeds, the state of healthy vineyard is stable, if removal and replacement
of infected plants is implemented. In the presence of hotbeds, depending on the grapevine density, we
find either a single family of equilibria in which the health of the vineyard gradually deteriorates for pro-
gressively more severe hotbeds, or multiple equilibria that give rise to sudden transitions from a nearly
healthy vineyard to a highly deteriorated one when the severity of the hotbeds crosses a critical value.
These results show the long-term risks in planting new vineyards in environmental situations where
strong hotbeds of FD are present or may arise in the surroundings
Acquisition and inoculation of FD phytoplasmas by adults of Scaphoideus titanus Ball: less time is required
No full textScaphoideus titanus Ball (Hemiptera: Cicadellidae) is the main vector of grapevine’s “Flavescence dorée” (FDP) phytoplasmas (16SrV, subgroups C and D). According to the state-of-art, nymphs acquire phytoplasmas from infected plants within a few days (acquisition access period, AAP), and undergo a latency period (LP) lasting 3-5 weeks. Afterwards the insects, meanwhile having mutate to adults, are able of infecting new plants following and inoculation access period (IAP) of a few days. However, some aspects of FDP epidemics suggest that adults may also acquire directly phytoplasmas and become infective within their lifespan. Therefore, transmission experiments have been carried out under lab conditions, using broad bean plants (Vicia faba L.) artificially infected with 16SrV-C phytoplasmas as a source of inoculum. Uninfected S. titanus adults were allowed to feed for 7 days (AAP) on infected plants. Afterwards, three inoculations on healthy broad beans were performed at 7 days intervals each (IAPs). At the end of each IAP, insects were moved on a new plant. Therefore, IAP 1, IAP 2 and IAP 3 lasted 7, 14 and 21 days from the end of AAP, respectively. Phytoplasma were identified in plants and insects by DNA extraction and PCR. Some insects were also dissected and fluorescent in situ hybridization was made to detect the presence of phytoplasmas in midguts and salivary glands. Infection in insects and plants ranged 46-68% and 16-23%, respectively. Neither showed significant differences among IAPs, whereas phytoplasma load was significantly higher in IAP3 for both plants and insects. Phytoplasmas were identified in both midgut and salivary glands. The whole transmission process has been therefore successful within just 14 days (AAP=7 + IAP=7). These new insights are consistent with severe FDP outbreaks at the end of the summer in grapevine growing areas, and may call for new pest management strategies against S. titanus
First record of the non-native Osbornellus auronitens (Provancher, 1889) (Hemiptera, Cicadellidae, Deltocephalinae) in Italy
No full textGlobalisation and international trade, in particular, are the major drivers of introduction and the spread of non-native species. To date, more than 30 species of non-native Hemiptera Auchenorrhyncha have been accidentally introduced into Europe. Some species are invasive with important repercussions primarily for agricultural activities, while almost no information exists on their impacts within natural ecosystems. Therefore, early detection of non-native species and their subsequent monitoring are extremely important actions to undertake.The North American Osbornellus auronitens (Provancher, 1889), firstly recorded for the Palearctic and Europe in Switzerland in 2016, is recorded in Italy for the first time on the basis of 77 specimens collected between August 2015 and October 2022
The mosaic leafhopper Orientus ishidae: host plants, spatial distribution, infectivity, and transmission of 16SrV phytoplasmas to vines
No full textOrientus ishidae (Matsumura) is an Asian species introduced into Europe and recently associated with 16SrV phytoplasmas, related to grapevine “flavescence dorée”. Its life cycle, host plants, spatial distribution, infection and vector capability have been investigated in vine-growing areas of Piedmont, NW Italy. The spatial distribution of adults in vineyards was studied by applying interpolation methods to trap capture data. Insects were subject to molecular analyses to verify phytoplasma presence and identity. DNA extraction and PCR were made to detect 16SrV phytoplasmas. Transmission experiments were set up, using different sources for phytoplasma acquisition, and two plant species and an artificial diet for inoculation. Whole mount in situ hybridization was made to detect phytoplasmas in the salivary glands of adults. In the vineyard agro-ecosystem, 19 plant species (11 families), mainly broadleaf trees and shrubs, were recognized as host plants of the insect. Adults were more abundant on putative host plants than on grapevines, with a clear clustering at the edges of vineyards, and without a massive intrusion into the vineyard from outside. 16SrV phytoplasmas were detected only in adults captured with yellow sticky traps (20 out of 188 tested). The transmission of 16SrV phytoplasmas was successful after phytoplasma acquisition from infected broad bean and inoculation on grapevine
Cluster Models for Studying CO<inf>2</inf> Reduction on Semiconductor Photoelectrodes
No full textSunlight-powered CO2-photoelectroreduction is a promising and potentially sustainable route to recycle CO2 byproducts back into energy-dense liquid fuels. One of the most intriguing processes known to date is the pyridinium-catalyzed CO2 reduction on p-type GaP photoelectrodes, where conversion to methanol has reported faradaic efficiencies nearing 100 %. Modeling this reactive environment requires understanding energetics of differently charged species at semiconductor electrodes, so we develop a cluster model and benchmark binding energies from it to those from Kohn–Sham density functional theory calculations that employ periodic boundary conditions. We then use this cluster model to theoretically predict structures and binding energies for charged and neutral adsorbates on the GaP(110) surface with and without the presence of van der Waals interactions and implicit solvation. We discuss the relative magnitudes of binding energy contributions for different adsorbates considered relevant in this CO2 reduction process and provide details showing pitfalls when using cluster models
Host plants and seasonal presence of Dictyophara europaea (Hemiptera: Dictyopharidae) in the vineyard agro-ecosystem
No full textMonitoring Scaphoideus titanus for IPM purposes: results of a pilot project in Piedmont (NW Italy). Bulletin of Insectology 64 (Supplement), 2011, S269-270.
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