Alan Oggier

Der aus Ostasien stammende Zitronenseitling (Pleurotus citrinopileatus) wird weltweit für eine Vielzahl von kulinarischen und medizinischen Anwendungen kultiviert. In einigen Ländern einschliesslich der Schweiz ist er von der Zucht in die Natur gelangt und in den Wäldern Nordamerikas hat er sich inzwischen massiv verbreitet. Über die Auswirkungen verwilderter Zuchtpilze auf die heimische Natur ist bislang nur sehr wenig bekannt, aber Pilzzüchter sollten dennoch darauf achten, ihre weitere Verbreitung im Freien möglichst zu unterbinden.

Il fungo Pleurotus citrinopileatus, originario dell'Asia orientale, è coltivato in tutto il mondo per diversi usi culinari e medicinali. In alcuni Paesi, tra cui la Svizzera, è stato introdotto dalla coltivazione in natura e, nelle foreste del Nord America, si è nel frattempo diffuso massicciamente. Si sa molto poco degli effetti dei funghi coltivati inselvatichiti sulla natura autoctona, ma i coltivatori di funghi dovrebbero comunque fare attenzione a prevenire il più possibile la loro ulteriore diffusione all'aperto.

'Candidatus Phytoplasma ulmi' (Ca. P. ulmi) belongs to the ribosomal subgroup 16SrV-A and is associated with dieback, shoot proliferation and yellows disease on various Ulmus spp. Other plant species, such as Carpinus betulus and Prunus spp. have also been reported infected by the same pathogen. In 2021, in the frame of research activities focused on grapevine's Flavescence dorée (FD), one specimen of Orientus ishidae - an East Palearctic leafhopper that was identified as an alternative vector of FD phytoplasmas - was found harboring Ca. P. ulmi in southern Switzerland. No phytoplasmas were detected in plant samples taken in the same location. Orientus ishidae has already been reported to be able to acquire diverse phytoplasmas associated with other plant diseases, such as Peach X-disease. This is the first report of Ca. P. ulmi in Switzerland, as well as in O. ishidae. Ca. P. ulmi may potentially be present in the wild compartment of the Swiss Pre-alpine and Alpine range, but no dedicated survey has so far been conducted. In the case of O. ishidae, this finding highlights the broad affinity of such a species for the acquisition of several phytoplasmas. This calls for a further investigation regarding its potential role as a vector on various pathosystems of agronomic importance.

“Flavescence dorée” (FD) is a quarantine grapevine disease associated with FD phytoplasmas (FDp). In Switzerland, FD was identified in 2004 in the southernmost part of Canton Ticino (TI) and then rapidly propagated throughout the entire regional winegrowing area despite the mandatory control measures. The reported widespread distribution of gone-wild grapevines (GWGV) in TI raised the hypothesis of a potential role of GWGV as an FDp reservoir and as a habitat for FDp vectors. To test this assumption, GWGV and FDp vectors were sampled in 13 plots to attest their infection status and compare the FDp genetic profiles. The primary (Scaphoideus titanus) and best-candidate alternative (Orientus ishidae) vectors were collected throughout the season and were found in moderate to high abundance in all the study area. The infection rate of both GWGV and S. titanus followed the historical gradient of S. titanus arrival and dispersal in TI with a clear geographic distinction between the southern and northern part of TI. Interestingly, the rate measured for S. titanus was similar to that observed in highly FD-infested cultivated vineyards. Moreover, the genetic profiles of the infected GWGV and S. titanus samples were identical to those commonly observed in cultivated vineyards (map M54). Importantly, four specimens of O. ishidae were also found harboring the same genotype. This study emphasizes the importance of GWGV (and abandoned vineyards) and alternative vectors for the FD epidemics in FD-infested regions, as well as a potential origin for FD outbreaks in areas currently designated as FDp-free.

Flavescence doree (FD) is a detrimental grapevine's disease, which leads to important economic losses to European viticulture. FD is associated with specific phytoplasmas (FDp), which are acquired and transmitted by the Nearctic leafhopper Scaphoideus titanus. No curative methods are currently available and so far, control measures have been targeted at the vineyard scale, disregarding the role of landscape as a possible source of inoculum and as a suitable habitat for the vector population. In fact, several alternative vectors and host plant species have been identified in the landscape as possible actors in the FD epidemics. In the specific case of Southern Switzerland, the East Palearctic leafhopper Orientus ishidae along with the plant species Alnus glutinosa have been recognized to play an active role in the maintenance of FDp in the landscape, while Corylus avellana was identified as the most suitable host for O. ishidae. Moreover, hazelnut was repeatedly found harboring FDp genotypes. During winter 2021/22, a habitat management experiment was conducted to assess the impact of selective coppicing and removal of hazelnuts for the control of O. ishidae. In the treated sites, the O. ishidae mean populations showed a marked decreasing trend, which went far beyond the seasonal reduction observed in most of the untreated sites, confirming the positive impact of the selective removal of hazelnuts. Habitat management may thus serve as an integrative tool to reduce the population of the alternative vector O. ishidae and the related risk of FDp flow between the forest and the cultivated compartments.

'Flavescence dorée' (FD) is a quarantine grapevine disease associated with FD phytoplasmas (FDp). In Switzerland, FD was first reported in 2004 in the southern part of the Canton Ticino, from where, within a few years, it spread to nearly the entire vineyard area of the Southern Alps, despite the mandatory control measures. The aim of this study was to assess the possible role of gone-wild grapevines (GWGVs) in forests resulting from early abandoned vineyards as a habitat for the main FDp vector, Scaphoideus titanus, and for the best alternative vector candidate, Orientus ishidae, as well as an FDp inoculum reservoir in Southern Switzerland. Leaf samples were collected in 20 plots and tested for the presence of FDp. Moreover, fifteen of these plots were monitored with yellow sticky traps to determine the presence and infection status of insect vectors. Finally, a hatching experiment under controlled conditions was conducted to investigate the possible oviposition activity by FDp vectors, using wood collected from GWGVs present in 11 forest sites in the surroundings of cultivated vineyards. GWGVs in forests were confirmed to act as an FDp reservoir and to represent a suitable habitat for FDp vectors (in particular, for S. titanus). Abandoned vineyards should be included in the FD management strategy and their systematic rogueing should be applied as soon as possible and in particular before the transition from vineyard to forest occurs, in order to avoid the survival of S. titanus and the establishment of inoculum in uncontrolled landscape compartments.

The first detection of grapevine's "flavescence doree" (FD) in Switzerland and the application of the mandatory control measures date back to 2004. The use of buprofezin allowed an optimal control of the insect vector Scaphoideus titanus. However, buprofezin has been banned since 2019 raising the need for an alternative control strategy. Assuming a slow S. titanus population growth in the first post-treatment years, the Swiss Canton of Ticino received the permission to suspend the mandatory insecticide treatments for two consecutive years, before resuming the insecticide sprayings with pyrethrins in the third year. This study aimed at assessing the impact of the suspension and resumption of treatments on the population dynamics of S. titanus and the consequences on the FD incidence in vineyards. The mean captures of S. titanus specimens increased eleven fold over the two-year period of treatment suspension, while the subsequent pyrethrins applications did not bring the populations back to the pre-suspension level. Nevertheless, the overall increments were not statistically significant (p > 0.05) mostly due to the variability in population density among vineyards. However, and most importantly, the incidence of infected grapevines remained stable. Under specific frame conditions, such as low initial vector populations and cultivation of less susceptible cultivars, adaptive management options may represent a possible alternative control strategy for an extensive use of insecticide applications in the vineyard agroecosystem.