“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 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.

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.

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.