Climate tolerances of Philaenus spumarius should be considered in risk assessment of disease outbreaks related to Xylella fastidiosa

The bacterium Xylella fastidiosa (Xf) is an invasive insect-borne pathogen, which causes lethal diseases to important crops including olives, citrus, almonds and grapes as well as numerous forest, ornamental, and uncultivated plants. Outbreaks of Xf-related plant diseases are currently occurring in the Mediterranean region, causing substantial losses to various agricultural sectors. Several models have recently been published to identify which regions are at highest risk in Europe; however, such models did not consider the insect vectors, which constitute the key driver of short-range Xf spread. We fitted bioclimatic species distribution models to depict the macroclimatic preferences of the meadow spittlebug Philaenus spumarius L. (1978) (Hemiptera: Aphrophoridae), the major epidemiologically relevant vector currently responsible for Xf spread in the Europe. Many regions of Western Europe and Mediterranean basin are predicted by models as highly climatically suitable for this vector, including all regions where severe Xf have occurred so far. Conversely, the driest and warmest areas of the Mediterranean basin are predicted as little suitable for P. spumarius. Models forecast that agricultural-important parts of the southern Mediterranean area might experience a substantial decrease in climatic suitability for P. spumarius by the period 2040–2060. Areas predicted as highly suitable just for the bacterium but not optimal for this vector are apparently still free of severe Xf outbreaks, suggesting that climate tolerances of P. spumarius might partly explain the current spatial pattern of Xf outbreaks in Europe and should always be considered in further risk assessments.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This work has been financially supported by the Spanish Ministerio de Ciencia, Innovación y Universidades, Grant/Award Number: AGL2017-89604-R and the European Union Horizon 2020 research and innovation program under grant agreements no. 635646 POnTE (Pest Organisms Threatening Europe), and no. 727987 XF-ACTORS (Xylella Fastidiosa Active Containment Through a multidisciplinary-Oriented Research Strategy). The first author of this study was funded by the fellowship “Ayudas destinadas a la atracción de talento investigador de la Comunidad de Madrid”. Daniele Cornara participation in this work was supported by a research grant in the frame of European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 835732 XYL-SPIT

Infectivity and Transmission of Xylella fastidiosa by Philaenus spumarius (Hemiptera: Aphrophoridae) in Apulia, Italy

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 Brulle 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

Depigmenting potential of lichen extracts evaluated by in vitro and in vivo tests

Melanin is the main pigment of human skin, playing the primary role of protection from ultraviolet radiation. Alteration of the melanin production may lead to hyperpigmentation diseases, with both aesthetic and health consequences. Thus, suppressors of melanogenesis are considered useful tools for medical and cosmetic treatments. A great interest is focused on natural sources, aimed at finding safe and quantitatively available depigmenting substances. Lichens are thought to be possible sources of this kind of compounds, as the occurrence of many phenolic molecules suggests possible effects on phenolase enzymes involved in melanin synthesis, like tyrosinase. In this work, we used four lichen species, Cetraria islandica Ach., Flavoparmelia caperata Hale, Letharia vulpina (L.) Hue, and Parmotrema perlatum (Hudson) M. Choisy, to obtain extracts in solvents of increasing polarity, viz. chloroform, chloroform-methanol, methanol, and water. Cell-free, tyrosinase inhibition experiments showed highest inhibition for L. vulpina methanol extract, followed by C. islandica chloroform-methanol one. Comparable results for depigmenting activities were observed by means of in vitro and in vivo systems, such as MeWo melanoma cells and zebrafish larvae. Our study provides first evidence of depigmenting effects of lichen extracts, from tyrosinase inhibition to cell and in vivo models, suggesting that L. vulpina and C. islandica extracts deserve to be further studied for developing skin-whitening products

Intruding into a conversation: how behavioral manipulation could support management of Xylella fastidiosa and its insect vectors

Behavioral manipulation (BM) is a multimodal control approach based on the interference with the stimuli mediating insect perception and interaction with the surroundings. BM could represent a win–win strategy for the management of vector-borne plant pathogens as the bacterium Xylella fastidiosa, since it could reduce the number of vectors alighting on host plants and, consequently, the chances for transmission to occur. In this review, we summarized current knowledge and highlighted gaps in information on (i) how insect vectors of X. fastidiosa in general, and more specifcally the meadow spittlebug Philaenus spumarius, locate and accept the host plant; and (ii) how behavioral manipulation techniques could be applied to disrupt the vector–host plant interaction. Finally, we discussed how diverse BM strategies could be combined with other integrated pest management tools to protect olive groves from inoculation with the fastidious bacterium

Analysis of vector behavior as a tool to predict xylella fastidiosa patterns of spread

The most likely scenarios for Xylella fastidiosa introduction in Central Europe is through infected ornamental plants, with a successive spillover from gardens and parks to cultivated orchards. Given its polyphagy and wide distribu-tion, the meadow spittlebug Philaenus spumarius, the only ascertained vector of X. fastidiosa in Europe so far, might play an important role in such a scenario. Here, we combined and analyzed spittlebug’s behavioral data obtained through Electrical Penetration Graph (EPG), preference and survival tests as well as field surveys, in order to infer possible bacterium patterns of spread. For our case study, we selected oleander and rosemary as potential introductory hosts and grapevine and cherry as economically important threatened plants. Philaenus spumarius was collected in field near all the four plant species, although choice and no-choice tests indicated that the spittlebug rather prefers to settle on cherry and grapevine than on rosemary and oleander. Considering the results of the EPG, the duration of xylem sap ingestion was longer in cherry, grapevine and rosemary than in oleander. However, P. spumarius spent on rosemary most of the time in resting activities, this implying a lower duration of xylem sap ingestion compared to grapevine and cherry. Overall, our data suggest that cultivated plants as grapevine and cherry could be more relevant than oleander and rosemary as X. fastidiosa source plants; therefore, P. spumarius might acquire the bacterium from cultivated plants, then first spread it within cultivated orchards, and successively to ornamental plants during its dispersal