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Scaphoideus titanus (Ball) is a Nearctic leafhopper (Cicadellidae: Deltocephalinae), monophagous on Vitis spp., naturalized in European vineyards since the 20th century. Following its introduction and establishment in Europe, S. titanus became the main vector of Flavescence dorée phytoplasma (FDp) to grapevine. FDp causes heavy economic losses to viticulture in Europe. The control of the disease mainly relies on insecticide applications against the vector and on the removal of infected plants. The exploitation of plant resistance or tolerance against pathogens and pests can represent a valuable tool for a more sustainable viticulture. The first step in identifying resistance traits in grapevine varieties towards S. titanus is the evaluation of insect fitness parameters on different grapevine genotypes. Therefore, in this work, nymph mortality and developmental time, adult survival and prolificacy of S. titanus have been studied on three grapevine varieties, characterized by different susceptibility to FD. Scaphoideus titanus showed highest fitness when reared on Barbera, whereas the worst performances were recorded on Moscato, with a significant reduction in nymph and adult survivals, a slowed nymph development, and a decreased number of available eggs. On Brachetto, S. titanus showed an intermediate level of fitness parameters. Consistently with previous studies on feeding behaviour, Barbera is the most suitable host for the FD‐vector. The high suitability of Barbera for S. titanus may partly explain the high susceptibility to FD of this variety. On the contrary, the low suitability of Moscato, poorly susceptible to FD, may be due to antibiosis and antixenosis defence mechanisms that act against S. titanus. [ABSTRACT FROM AUTHOR]

BACKGROUND RNA interference (RNAi) techniques have emerged as powerful tools to develop novel management strategies for the control of insect pests. The leafhopper Euscelidius variegatus is a natural vector of chrysanthemum yellows phytoplasma and a laboratory vector of Flavescence dorée phytoplasma. Phytoplasmas are insect‐borne bacterial plant pathogens that cause economically relevant crop losses worldwide. RESULTS: In this study, we demonstrated that microinjection of muscle actin and ATP synthase β double‐stranded (ds)RNAs into adult insects caused an exponential reduction in the expression of both genes, which began within 72 h of dsRNA administration and lasted for 14 days, leading to almost complete silencing of the target genes. Such silencing effects on muscle actin expression appeared to be both time‐ and dose‐dependent. Our results also showed that the knockdown of both genes caused a significant decrease in survival rates in comparison with green fluorescent protein (GFP) dsRNA‐injected control insects. CONCLUSION: The effectiveness of RNAi‐based gene silencing in E. variegatus guarantees the availability of a powerful reverse genetic tool for the functional annotation of its genes and the identification of those potentially involved in the interaction with phytoplasmas. In addition, this study demonstrated that muscle actin and ATP synthase β may represent candidate genes for RNAi‐based control of E. variegatus. © 2018 Society of Chemical Industry Microinjection of muscle actin and ATP synthase β double‐stranded (ds)RNAs in the phytoplasma insect vector Eeuscelidius variegatus caused an exponential reduction in the expression of both genes and a significant decrease in insect survival. [ABSTRACT FROM AUTHOR]

BACKGROUND Acibenzolar- S-methyl ( BTH), a functional analogue of salicylic acid ( SA), is known to elicit a systemic resistance across a broad range of plant-pathogen interactions, but so far it has not been tested against flavescence dorée ( FDP), one of the most devastating grapevine diseases. The aim of this work was to evaluate the activity of BTH in preventing FDP transmission by the insect vector and in inducing recovery of infected grapevines. RESULTS Repeated 2 mM applications of BTH to test grapevine cuttings (cv. Barbera) exposed to adults of the infectious vector Scaphoideus titanus Ball reduced the rate of infected plants. The effect was not recorded following similar BTH applications to highly susceptible young in vitro propagated vines. A high natural recovery rate (more than 70%) was observed over a 3 year period in field-infected grapevines of the same cultivar. Under these conditions, BTH repeated applications over the whole period clearly failed to increase recovery of field-infected grapevines. CONCLUSION Following a 3 year experiment, it can be concluded that, although high doses and repeated applications of BTH reduced vector transmission of FDP, BTH was ineffective in inducing recovery of FDP-infected grapevines cv. Barbera under field conditions. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Phytoplasmas are plant-pathogenic Mollicutes transmitted by leafhoppers, planthoppers, and psyllids in a persistent propagative manner. Chrysanthemum yellows phytoplasma (CY) is a member of ‘ Candidatus Phytoplasma asteris’, 16Sr-IB, and is transmitted by at least three leafhopper species, Macrosteles quadripunctulatus Kirschbaum, Euscelidius variegatus Kirschbaum, and Euscelis incisus Kirschbaum (all Homoptera: Cicadellidae: Deltocephalinae). Although M. quadripunctulatus transmits CY with very high efficiency (near 100%), 25% of E. variegatus repeatedly fail to transmit CY. The aims of this work were to correlate vector ability with different pathogen distribution in the insect body and to investigate the role of midgut and salivary glands as barriers to CY transmission. Euscelidius variegatus individuals acquired CY by feeding on infected plants or by abdominal microinjection of a phytoplasma-enriched suspension. Insects were individually tested for transmission on daisy seedlings [ Chrysanthemum carinatum Schousboe (Asteraceae)], and thereafter analysed by real-time polymerase chain reaction (PCR) for CY concentration on whole insects or separately on heads and the rest of the body. Hoppers were classified as early and late transmitters or non-transmitters, according to the time inoculated plants required for expression of CY symptoms. Similar transmission efficiencies were achieved following feeding or abdominal microinjection, suggesting that salivary glands may be a major barrier to transmission. Following acquisition from infected plants, all transmitters tested positive by PCR, and 60% of non-transmitters also tested positive although with a significantly lower CY concentration. This indicates that a minimum number of phytoplasma cells may be required for successful transmission. The midgut may have prevented phytoplasma entry into the haemocoel of PCR-negative non-transmitters. Results suggest that both midgut and salivary glands may act as barriers. To assess the effect on CY transmission of a specific parasitic bacterium of E. variegatus, tentatively named BEV (Bacterium Euscelidius variegatus), we established a BEV-infected population by abdominal microinjection of BEV bacteria. The presence of BEV did not significantly alter the efficiency of CY transmission. [ABSTRACT FROM AUTHOR]