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The recent history of Xylella fastidiosa Wells et al. introduction in Europe illustrates how the lack of knowledge about the bacterium‐vector‐host interactions hinders the application of effective containment strategies, with the bacterial spread that currently appears relentless. Vector behavior is a key component in plant pathogen transmission; therefore, detailed knowledge of vector probing behavior on various host plants would furnish useful data for containing the bacterium. Aiming at this goal, we carried out electrical penetration graph (EPG)‐assisted probing behavior observations of the spittlebug, Neophilaenus campestris (Fallen) (Hemiptera: Aphrophoridae), a candidate vector widespread in all the areas where X. fastidiosa is currently established. Spittlebug probing was first characterized on one of its preferred host plants, Bromus madritensis L. (Poaceae), over short (6 h) and long (16 h) time spans. Thereafter, we performed comparative observations of the spittlebug probing on B. madritensis, olive, and grapevine. Overall, the probing behavior of N. campestris, that is, the main characteristic waveforms, did not differ substantially from that of Philaenus spumarius (L.) (Hemiptera: Aphrophoridae); however, here we report and describe a new kind of xylem activity interruption, provisionally termed N2, not previously observed in P. spumarius. Considering the time spent in xylem ingestion as a percentage of the total probing time (host‐suitability indicator used for spittlebugs), grapevine and B. madritensis are the preferred hosts for N. campestris, with olive as the least suitable among the plants tested. Successful probes, that is, probes during which xylem ingestion occurred, on grapevine were 2.5× greater than olive. Therefore, our data on N. campestris probing behavior suggest that the spittlebug role in X. fastidiosa epidemiology in European vineyards should be given more attention. In the present manuscript, we also discuss the current difficulties in interpreting and analyzing the outcomes of EPG studies on spittlebugs. [ABSTRACT FROM AUTHOR]

The recent emergence of Xylella fastidiosa in Europe is a major threat to agriculture, including olive, almond and grape. Philaenus spumarius is the predominant vector of X. fastidiosa in Europe. Understanding vector movement is critical for developing effective control measures against bacterial spread. In this study, our goal was to set up a flight-mill protocol to assess P. spumarius flight potential and to analyse how different variables may affect its flight behaviour. We found that P. spumarius was able to fly ≈ 500 m in 30 min with a maximum single flight of 5.5 km in 5.4 h. Based on the observations, the flight potential of the females was higher in spring and autumn than in summer, and that of the males was highest in autumn. Moreover, we found that P. spumarius had a higher flight potential during the morning and the night than during the afternoon. Our results revealed that P. spumarius is likely to disperse much further than the established sizes of the infected and buffer zones designated by the EU. This knowledge on the flight potential of P. spumarius will be critical for improving management actions against P. spumarius and the spread of X. fastidiosa in Europe. [ABSTRACT FROM AUTHOR]

Here, we provide the first insights into the transmission dynamics of the bacterium Xylella fastidiosa by the meadow spittlebug Philaenus spumarius, gathered through DC EPG (electrical penetration graph)-assisted transmission tests and comparative observations of the probing and feeding behavior of infective versus non-infective vectors on healthy olive plants. Bacterial cells binding to P. spumarius' foregut occurred at a very low rate and in a time as short as 15 min spent by the insect in xylem ingestion or activities interspersed with xylem ingestion (interruption during xylem ingestion and resting). P. spumarius inoculation of bacterial cells into the xylem was exclusively associated with an early (ca. 2 to 7 min after the onset of the first probe) and occasional behavior, provisionally termed waveform Xe, presumably related to egestion regulated by pre-cibarial valve fluttering. Infective spittlebugs compared to non-infective ones exhibited: (i) longer non-probing and shorter xylem ingestion; (ii) longer duration of single non-probing events; (iii) fewer sustained ingestions (ingestion longer than 10 min) and interruptions of xylem activity (N); and (iv) longer time required to perform the first probe. These observations suggest difficulties in feeding of infective P. spumarius probably caused by the presence of X. fastidiosa within the foregut. Overall, our data indicate that likely short time—few minutes—is required for X. fastidiosa transmission by P. spumarius; thus, vector control strategies should aim at preventing spittlebug access to the host plant. Furthermore, our findings represent an important contribution for further research on the disruption of spittlebug–bacterium interactions. [ABSTRACT FROM AUTHOR]

Artificial diets represent an essential tool for investigations on the intimate relationship between plant pathogens and their vectors. Previous research failed in devising an artificial diet delivery system for the meadow spittlebug Philaenus spumarius, to date considered the most important vector of the bacterium Xylella fastidiosa in Europe. Here, we describe a new delivery "tube system" by which we succeeded in artificial feeding of P. spumarius with holidic diets (one sucrose diet and two amino acids diets). Spittlebug probing and feeding behaviour on either the tube system or a traditional "flat system" realized out of a small Petri dish filled with diet and covered with stretched Parafilm® were observed in real time by video‐EPG (Electrical Penetration Graph), in order to assess the occurrence of ingestion and excretion. Moreover, we evaluated P. spumarius survival on either the tube system filled with the two holidic diets that gave the best EPG results or an empty tube system serving as control. Contrary to the flat system, where just brief stylet insertions through the Parafilm® were recorded, the spittlebug ingested the artificial diets when delivered with the tube system. Survival on the diets provided with the tube system was significantly greater than the control, with no differences between the diets tested. Furthermore, the tube system was suitable also for another spittlebug species shown to be a competent vector of X. fastidiosa, that is Neophilaenus campestris. The tool we devised opens new perspectives for investigations on X. fastidiosa/spittlebugs interactions, as well as for the functional analysis of mutant X. fastidiosa strains in respect to insect colonization and transmission. [ABSTRACT FROM AUTHOR]

The meadow spittlebug Philaenus spumarius plays a key role in the transmission of the bacterium Xylella fastidiosa to olive in Apulia (South Italy). Currently, available data on P. spumarius feeding behavior is limited, and a real-time observation of the different steps involved in stylet insertion, exploratory probes, and ingestion, has never been carried out. Therefore, we performed an EPG-assisted characterization of P. spumarius female feeding behavior on olive, in order to detect and analyze the main EPG waveforms describing their amplitude, frequency, voltage level, and electrical origin of the traces during stylet penetration in plant tissues. Thereafter, each of the main waveforms was correlated with specific biological activities, through video recording and analysis of excretion by adults and excretion/secretion by nymphs. Furthermore, the specific stylet tips position within the plant tissues during each of the waveforms observed was assessed by microcomputer tomography (micro-CT). Additional EPG-recordings were carried out with males of P. spumarius on olive, in order to assess possible sex-related differences. P. spumarius feeding behavior can be described by five main distinct waveforms: C (pathway), Xc (xylem contact/pre-ingestion), Xi (xylem sap ingestion), R (resting), N (interruption within xylem phase). Compared to males, females require shorter time to begin the first probe, and their Xi phase is significantly longer. Furthermore, considering the single waveform events, males on olive exhibit longer np and R compared to females. [ABSTRACT FROM AUTHOR]

The threat imposed by the bacterial pathogen Xylella fastidiosa to crops of utter importance to European agriculture such as olive, stone fruit and grapevine calls for immediate research against the meadow spittlebug, Philaenus spumarius (L.), the main European vector. Management tools should consider reducing juveniles of vector populations growing on weeds or cover crops during spring as nymphs have limited movement and do not contribute to disease spread. We examined a wide range of insecticides with different modes of action against P. spumarius nymphs in laboratory and semi-field glasshouse conditions. Pyrethroids (delthamethrin and λ-cyhalothrin) and natural pyrethrin (Pirecris®) + piperonyl butoxide (PBO) efficacy surpassed 86% after 24 h of exposure, without significant differences in the PBO amount tested. The inclusion of PBO caused a 3-fold increase in the mortality of P. spumarius nymphs compared to pyrethrin alone. Sulfoxaflor (Closer®) exhibited similar efficacy at 48 and 72 h but it was slow acting and mortality only reached 60% at 24 h. The LC90 was 34 ppm at 72 h. Pymetrozine, spirotetramat, azadirachtin and kaolin were not effective against nymphs (mortality <33%) although in azadirachtin-treated plants, mortality had a 3-fold increase from 24 to 72 h. Our results will help decision-making policy bodies to set up a sustainable integrated pest management of P. spumarius in areas where X. fastidiosa becomes a problem. [ABSTRACT FROM AUTHOR]