The bois noir (BN) disease of grapevines is widespread in German winegrowing regions. It is associated with ‘Candidatus Phytoplasma solani’, which affects not only grapevines but also other wild and cultivated plants. This pathogen has a complex epidemiology including different insect vectors and various host plants. A study was carried out to investigate the genetic variability of ‘Ca. P. solani’ in different winegrowing regions in Germany. Between 2017 and 2023, samples of grapevine, stinging nettle, bindweed, and other herbaceous plants as well as specimens of different planthopper species colonizing viticultural habitats were analyzed for infection with ‘Ca. P. solani’. All positive tested samples were further characterized by multilocus sequence typing (MLST) based on the genes tuf, stamp, secY, and vmp1. The genetic variability was assessed by RFLP analyses of the tuf and vmp1 PCR products, coupled with sequencing of the stamp and secY amplification products. A total of 1274 grapevines, 35 bindweed, and 18 stinging nettle samples were infected with ‘Ca. P. solani’ but also five samples of other weed species. Among the known and putative insect vectors, specimens of Hyalesthes obsoletus, Reptalus spp., and Dictyophara europaea harbored the phytoplasma. In both plants and insects, two genotype combinations were predominantly associated with the classical bindweed and stinging nettle cycle, respectively. The MLST analysis revealed considerable differences between German isolates and data reported from other European regions and new genotype combinations were identified, indicating new host plant–vector associations.

The vineyards of Palatinate (Germany) and Alsace (France) in the Upper Rhine valley are still free from Flavescence dorée (FD) disease, but the main vector in grapevine, the leafhopper Scaphoideus titanus, has recently been detected. Knowledge of reservoir plants and alternative vectors of FD phytoplasmas (FDp) is crucial for management strategies. An interregional survey showed that among 12 main wild woody plants and liana species sampled in the environments of vineyards, only alders were infected by FDp, with high prevalence of MAP-FD2 genotypes. Yellow sticky traps were used to record the abundance and analyze the natural infection rate of potential leafhopper vectors on alders, clematis and cultivated grapevine. Live specimens were collected for inoculation trials. High infection rates and transmission capacities of resident Allygus spp. and the invasive Orientus ishidae were confirmed. In addition, five other Deltocephalinae species were identified as potential vectors of FDp. Lamprotettix nitidulus showed a high abundance and high infection rates with FDp in both regions. Its transmission competence of FDp to alder and broad bean could be demonstrated through repeated trials and high FDp titers were measured in infective individuals. Similar titers were measured in Synophropsis lauri, suggesting it could also transmit FDp. Fieberiella florii, Euscelidius variegatus and Japananus hyalinus may also play a role for the spread of 16SrV group phytoplasmas. Six new MAP-FD1 and FD2 genotypes were detected in leafhoppers. The prevalent and only transmitted genotype was M38: a vectotype II compatible with S. titanus transmission. The results show that the natural spread of FDp among alders is more complex than previously thought, and thus, the risk of transmissions to grapevine is more difficult to evaluate.

Xylem‐feeding is apparently the only requirement making an insect a competent vector of the bacterium Xylella fastidiosa , an organism responsible for the devastation of the Southern Italian olive forest and nowadays considered one of the most feared threats to agriculture and landscape in Europe, including vineyards. Here, we used the direct current‐electrical penetration graph (DC‐EPG) technique to compare and describe the feeding behaviour on grapevine of four xylem‐feeding species considered candidate vectors of X. fastidiosa widespread in Europe, namely two spittlebugs (the meadow spittlebug Philaenus spumarius and the spittlebug Neophilaenus campestris ) and two sharpshooter leafhoppers (the rhododendron leafhopper Graphocephala fennahi and the green leafhopper Cicadella viridis ). We created a standard for the analysis of EPG waveforms recorded with a DC‐EPG device, describing feeding activities performed by these insects from stylet insertion into the plant to withdrawal. This standard, along with freely available software, has been developed to harmonize the calculation of feeding behavioural parameters in xylem‐feeders. The most relevant differences between the two vector taxa were the probing frequency and the dynamics of xylem ingestion. Sharpshooters tended to perform significantly more probes than spittlebugs. In contrast, the latter spent longer times in low‐frequency xylem ingestion, characterized by scattered contractions of the cibarial dilator muscle interspersed with periods of pump inactivity. Cicadella viridis was the species displaying the highest frequency of the electrical pattern found to be associated with X. fastidiosa inoculation in spittlebugs (Xe). Feeding behavioural data presented here represent an important step forward for deepening our knowledge of xylem‐sap feeding insects' interaction with both the host plants and the bacterium they transmit.

“Flavescence dorée” (FD)-related phytoplasmas are widespread in alder in Germany and their transmission to grapevine represents a high risk for FD outbreaks when the primary vector, Scaphoideus titanus, becomes present in the future. Therefore, the potential role of the Deltocephalinae leafhopper species in transmitting FD-related phytoplasmas from alder to grapevine was studied in extensive transmission trials conducted between 2017 and 2020. The transmission capacity of autochthonous Allygus spp. and the invasive Orientus ishidae captured on infected alder trees was tested under controlled conditions using various test designs, including grouped insects and single-insect studies. The latter experiments were analyzed in terms of survival probability, transmission success and phytoplasma load in the insects, measured by quantitative PCR. A minimum inoculation titer (MIT) required for successful transmission to alder was defined for both Allygus spp. and O. ishidae. While Allygus spp. exhibited slightly better survival on Vitis vinifera compared to O. ishidae, the latter displayed higher phytoplasma loads and greater transmission success. Although all species were capable of infecting alder seedlings, O. ishidae was able to transmit 16SrV-phytoplasmas directly to single grapevines. Infective adults of O. ishidae were captured from the beginning of July until the end of August, while Allygus spp. were only considered infective towards the end of the season. Thus, O. ishidae likely poses a higher risk for FD transmission from alder to grapevine, albeit at a very low level, as only five out of 90 transmission trials to V. vinifera were successful.

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 2.5x 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.

The identification of volatile organic compounds (VOCs) leading to short-range attraction and oviposition of the European grapevine moth Lobesia botrana and European grape berry moth Eupoecilia ambiguella (Lepidoptera: Tortricidae) is crucial in order to establish bait-based decision support systems for control of these pests. Therefore, we developed a method to measure the real-time behavioral response of female moths to VOCs using a four-chamber olfactometer coupled with a video tracking system. Ten synthetic VOCs were selected for this study: (S)-(−)-perillaldehyde, (E)/(Z)-linalool oxide, (±)-limonene, linalool, (E)-β-caryophyllene, α/β-farnesene, (−)-α-cedrene, methyl salicylate and cumene. The effect of VOCs on egg deposition was determined using a dual-choice oviposition test, whereas perception by female antennae was verified using electroantennography (EAG). During video tracking, females responded to volatile compounds emitted by grapevine with higher antennae and ovipositor activity than to air control. (E)/(Z)-linalool oxide, cumene and (S)-(−)-perillaldehyde released ovipositor activity of L. botrana, while the latter provoked oviposition. (R)/(S)-limonene affected ovipositor activity of E. ambiguella, whereas none of the VOCs tested attracted for oviposition. The results suggest that females have the ability to perceive specific VOCs by the antennae but also by the ovipositor, which could attract or repel for egg deposition.

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.

The tortricid moths Lobesia botrana (Denis and Schiffermueller) and Eupoecilia ambiguella (Hübner) are major insect pests of grapevine Vitis vinifera. We compared the pattern of volatile organic compounds in headspace samples of four different grapevine cultivars in dependency of their phenological stage by thermodesorption coupled with gas chromatography (GC) and mass spectrometry. Further, we assessed the detection of compounds by the antenna of both moth species by GC coupled with electroantennographical detection. We detected significant differences between the chemical compositions of headspace samples of the four cultivars based on the odor bouquet. By comparing the principal component linear discriminant analysis pattern of only those chemical compounds that could be actually detected by the moths’ antenna, the different cultivars showed similar odor patterns indicating that differences measured by GC may not be detected by the moths’ antenna. The supposed reduced discriminatory ability of both moth species was supported by behavioral bioassays using a Y-tube olfactometer. In connection to the recently published impact of the berries’ visual appearance (shape and color) and nonvolatile compounds of the wax layer, the presented results suggest that reported moth preferences for specific cultivars are not encoded by volatiles only. The results of this study will contribute to the development of an innovative egg-monitoring tool for grapevine moths.

The Gram-negative bacterium Xylella fastidiosa causes disease in a number of important crops and plants within natural ecosystems. Most notable among these diseases are Pierce's disease of grapevine, Citrus Variegated Chlorosis, Almond Leaf Scorch, Oleander Leaf Scorch and Olive Quick Decline Syndrome. In response to substantial economic losses, extensive research efforts have been underway over the past several decades in North and South America. Recently, X. fastidiosa has been detected in several countries of Europe and Asia, likely appearing as a result of global trading of plant material. Once established in a new region, X. fastidiosa spread is dependent on the obligate transmission by xylem-sap feeding insects. Sharpshooter leafhoppers (Hemiptera: Cicadellidae: Cicadellinae) are the best-studied group of vectors of this bacterium; however the list of known vector species is expanding. As X. fastidiosa moves into new regions, the combination of an introduced pathogen with existing or introduced vectors carries the potential of increasing economically important disease problems in the local context. By reviewing ecological and biological information of known X. fastidiosa vectors and the epidemiology of local X. fastidiosa outbreaks, this paper aims at increasing our understanding of vector- X. fastidiosa interactions.

Grapevine moths are severe pest insects in European viticulture. Oviposition by grapevine moths is largely influenced by several physical and chemical cues located on the surface of their host plant’s fruits. The contribution of waxy bloom layer on the berry surface for oviposition decision of two European grapevine moth species, Eupoecilia ambiguella and Lobesia botrana, was investigated. An experimental setup was developed to prove oviposition preferences of both species for certain grape varieties and developmental stages based on epicuticular wax extracts. Chemical analysis of epicuticular wax patterns of four different Vitis vinifera varieties revealed differences. However, oleanolic acid was the main component on berry surface waxes and its relative amount decreased between early and late phenological stages. Furthermore, oleanolic acid was responsible for the preference of earlier phenological stages for E. ambiguella oviposition. However, ovipositional variety preferences were triggered by minor components on the wax berry layer. While the oviposition decision of L. botrana was mainly triggered by oleanolic acid, additional cues like olfactory and haptic ones were also important. The ovipositional preferences were discussed in accordance with the results of the chemical analysis in order to elucidate the role of wax compounds for oviposition stimulation.

Uncovering the entire process of oviposition could enable the development of innovative pest control strategies. The European grapevine moth Lobesia botrana as well as the European grape berry moth Eupoecilia ambiguella are serious insect pests, which still threaten viticulture in many parts of the world. By creating an artificial semiochemical emitting surface, in form of a card, we tried to develop an egg-monitoring tool for the oviposition of these two species in vineyards. The idea was to create a decision support system that facilitates timing and necessity of insecticide treatments. This article deals exclusively with the initial step towards the development of this tool: the influence of physical factors (colour, shape or texture) of a surface on the oviposition behaviour of L. botrana and E. ambiguella under laboratory conditions. The acceptance of different artificial substrates as oviposition site was analysed exclusive of volatile organic compounds emitted by a host plant. We investigated particular colours of the surface, which could be a visual stimulus to trigger the oviposition of both species. Apparently, the colour green, the texture of the material and the light conditions turned out to be highly important stimuli for oviposition.