Detecting and managing “Flavescence dorée” phytoplasma inoculum at landscape level – Flavid II

• Research unit: FOAG
• Project number: 21.01

Key words (German)

Quarantäneorganismus, Risikobewertung, integriertes Management, beste Praktiken, Reduzierung von Insektiziden

Key words (English)

quarantine organism, risk assessment, integrated management, best practices, insecticide reduction

Key words (French)

organisme de quarantaine, évaluation des risques, gestion intégrée, meilleures pratiques, réduction des insecticides

Key words (Italian)

organismo da quarantena, valutazione del rischio, gestione integrata, migliori pratiche, riduzione degli insetticidi

Short description (German)

Flavescence dorée" (FD) ist eine Quarantänekrankheit, die durch das FD-Phytoplasma (FDp) verursacht wird und erstmals in den 1950er Jahren im Südwesten Frankreichs gemeldet wurde. In Europa ist sie heute in den meisten Weinbaugebieten verbreitet, trotz der systematischen obligatorischen Bekämpfung, die hauptsächlich aus Insektizidanwendungen gegen den FDp-Insektenvektor und der Entfernung infizierter Rebstöcke besteht. Obwohl in Europa die epidemische Übertragung von FDp in Weinbergen durch den nearktischen Blattzikade Scaphoideus titanus erfolgt, haben sich bisher auch andere Auchenorrhyncha-Arten sowie mehrere Laubholzarten als mit verschiedenen FDp-Stämmen infiziert erwiesen.

All dies deutet darauf hin, dass die FDp-Epidemie ein komplexes System darstellt, das sich nicht auf die binomische Beziehung "Weinrebe - S. titanus" innerhalb des Weinbergs beschränkt. Wildgehölze und Wald rund um die Weinberge könnten zum Beispiel eine wichtige Rolle bei der Erhaltung des FDp-Inokulums in der Landschaft spielen.

Mit diesem Projekt soll man aufbauend auf den Erkenntnissen aus der Flavid-I Studie “Integrating alternate host plants and vectors in the modelling approach of the Flavescence dorée epidemiology” das Wissen über potentielle und bisher unentdeckte FDp-Reservoire in und auserhalb von Weinbergen vertiefen werden und dabei geprüft werden, ob Habitatmanagement-Massnahmen an der Schnittstelle Weinberg-Wald dazu beitragen können, das FDp-Inokulum zu senken.

Short description (English)

“Flavescence dorée” (FD) is a quarantine disease caused by the FD phytoplasma (FDp), which was first reported in the 1950s in Southwestern France. In Europe, it is now spread in most vineyard areas despite the systematic mandatory control mainly consisting of insecticide applications against the FDp insect vector, and the removal of infected grapevines. Although in Europe the epidemic transmission of FDp in vineyards occurs through the Nearctic leafhopper Scaphoideus titanus, other Auchenorrhyncha species as well as several deciduous woody species have resulted to be infected by different FDp strains so far.
All this indicates that the FDp epidemics and ecology may be better represented as a complex system that is not limited to the binomial “grapevine – S. titanus” relationship within the vineyard. In particular, the presence of woody species and forest in the landscape surrounding vineyards could play an im-portant role in increasing the pressure of the FDp inoculum for grapevines.
This project aims to deepen the knowledge about potential and so far undetected FDp reservoirs in and outside vineyards and to test if habitat management measures at the vineyard-forest interface may contribute to lower the epidemic pressure in terms of FDp inoculum. The project will profit from the results acquired in the Flavid I - study (“Integrating alternate host plants and vectors in the modelling approach of the Flavescence dorée epidemiology”).

Abstract (English)

“Flavescence dorée” (FD) is a quarantine disease associated with FD phytoplasmas (FDp, ‘Candidatus Phytoplasma vitis’) that causes severe production losses to European viticulture. The Nearctic leafhopper Scaphoideus titanus was identified as the vector responsible for the epidemic spread in vineyards, but secondary epidemiological cycles and alternative FDp vectors, such as Orientus ishidae, were identified.

In Switzerland, FDp is endemic in the Swiss southern Alps and its vector, S. titanus, is subjected to mandatory containment strategies. In the western and northern part of the country, FD is either already present and spreading or currently absent from cultivated vineyards, but sporadically present in the surrounding landscape.

The FLAVID II project aimed at enhancing the understanding of potential FDp reservoirs within and outside vineyards and consisted of the following three modules:

 

1.1     Analysis of the role of the vegetative strips (meadows hosting dicots) inside the vineyard plots (interrow) and between the vineyard and forest edges as reservoirs of FDp and as surviving habitat for the main FDp vector S. titanus, which may here elude insecticide applications.

1.2     Assessment of the potential role of abandoned vineyards and gone-wild grapevines that may act as FDp reservoirs and as S. titanus habitat.

2        Assessment of the impact of habitat management measures on the FD epidemics through the elimination from the forest edge-vineyard interface of woody plants acting as potential host of FDp vectors (e.g., hazel).

2. Main results

 

2.1 Module 1.1

1. Correctly and timely applied insecticide treatments allow not only to reduce the S. titanus populations on grapevine canopies but also to prevent the migration of individual specimens to the floor vegetation within the vineyard. Under these conditions, the interrow and the herbaceous interface between vineyard and forest do not appear to constitute a potential refuge for the main FDp vector.
2. A consistent number of O. ishidae individuals, an alternative FDp vector, was found inhabiting the forest edge surrounding cultivated vineyards.

 

2.2 Module 1.2

1. Semi-natural areas hosting gone-wild grapevines are widespread in southern Switzerland, some of them originating from vineyards abandoned up to a century ago.
2. Some of these gone-wild grapevines were found to host a considerable population of S. titanus and of the alternative vector O. ishidae, and to be FDp infected.
3. Some FDp genetic profiles found in gone-wild grapevines, FDp vectors, and cultivated vineyards in Canton Ticino are identical.
4. The presence of infected plant material and vectors confirms the potential role of gone-wild grapevines and abandoned vineyards in general as a FDp reservoir.

 

2.3 Module 2

1. Corylus avellana (hazel) has been confirmed as a preferential host plant for O. ishidae.
2. Habitat management measures can effectively reduce the populations of this alternative FDp vector on the forest edge and, at least indirectly, also within cultivated vineyards.
3. The applied measures have a lasting impact over time and do not require yearly management.

 

2.4 Additional unplanned results

1. First detection of ‘Candidatus Phytoplasma ulmi’ in Switzerland and in Orientus ishidae Matsumura, 1902.
2. First identification of ‘Candidatus Phytoplasma fragariae’ infecting Corylus avellana in southern Switzerland.
3. First record of the Nearctic leafhopper species Jikradia olitoria Say, 1830 in Switzerland

Transfer and application (English)

FLAVID II allowed us to confirm the intricate nature of FDp epidemiology, suggesting that the conventional disease model encompassing the pathogenic agent (phytoplasmas), the primary vector (S. titanus), and the host plant (cultivated grapevine) is not comprehensive enough to explain the spread and resilience of FD in southern Switzerland. The hypothesized FDp flow between different landscape compartments may partly explain the limited success of current containment measures, urging policy makers and stakeholders to reevaluate the current containment and eradication strategy, e.g., by intensifying the efforts in managing gone-wild grapevines and ensuring vines’ rogueing in case of future vineyard abandonments.

Applying the new findings acquired in FLAVID II to the vineyard area of western and northern Switzerland, where FD is either just arrived and spreading or currently absent, may allow to be more effective in detecting FD presence and assess the potential risk of a FDp inoculum and vectors flow between the vineyard and forest compartments. This proactive approach could be of high benefit especially in areas where disease eradication or prevention are the primary objectives.

Knowlegde improvements / Publications (English)

List of publications

Oggier, A., Conedera, M., Jermini, M., & Rizzoli, A. (2022). Rôle de la flore des vignobles comme refuge de Scaphoideus titanus et Orientus ishidae. Vignes et Vergers, 10, 12–14.

Oggier, A., Conedera, M., Jermini, M., Debonneville, C., Schumpp, O., & Rizzoli, A. (2023). Gone-wild grapevines in forests may act as a potential habitat for ’Flavescence dorée’ phytoplasma vectors and inoculum. Journal of Applied Entomology, 147, 9, 777–789. DOI: 10.1111/jen.13169

Oggier, A., Jermini, M., Conedera, M., Debonneville, C., Schumpp, O., & Rizzoli, A. (2023). Habitat management as an integrative tool for the control of grapevine’s Flavescence dorée. Extended abstract. IOBC-WPRS, 38–38.

Oggier, A., Debonneville, C., Conedera, M., Schumpp, O., & Rizzoli, A. (2024). First detection of ‘Candidatus Phytoplasma ulmi’ in Switzerland and in Orientus ishidae Matsumura, 1902. Alpine Entomology, 8, 29–34. DOI: 10.3897/alpento.8.115588

Oggier, A., Debonneville, C., Conedera, M., Schumpp, O., & Rizzoli, A. (2024). Scaphoideus titanus and Orientus ishidae on gone-wild grapevines share phytoplasma genotypes linked to the “Flavescence dorée” epidemics in cultivated vineyards. European Workshop on “Flavescence Dorée” - Recent Acquisitions and Management Strategies, 49–50.

Oggier, A., Jermini, M., Conedera, M., Debonneville, C., Schumpp, O., & Rizzoli, A. (2024). Habitat management as an integrative tool for the control of grapevine’s Flavescence dorée. Integrated Protection in Viticulture IOBC-WPRS Bulletin Vol. 171, 81–84.

Rizzoli, A., Oggier, A., Jermini, M., Battelli, R., Debonneville, C., Schumpp, O., & Conedera, M. (2023). Adaptive management trials for the control of Scaphoideus titanus, main vector of “flavescence dorée” phytoplasmas. Phytopathogenic Mollicutes, 13, 1.

Rizzoli, A., Debonneville, C., Linder, C., Kehrli, P., Bernasconi, L., & Pouvreau, E. (2023). Jaunisses de la vigne: Flavescence dorée et Bois noir - description, biologie et lutte. Vignes et Vergers, 3, 28–30.