Incurable flavescence dorée disease carrier took 17 years to move from Geneva to heart of Valais
GENEVA, SWITZERLAND – A leafhopper that can carry an incurable disease which withers grapes and turns vine leaves yellow has reached canton Valais, and while it took 17 years to get there from Geneva, the news is not good.
The federal agriculture office (FAO) Monday warned Swiss wine grape growers to be on the alert and to plant only certified, healthy plants from elsewhere.
The disease was for a long time limited to southern Europe, mainly southern France, Spain and Italy. It can cut harvests significantly and greatly weaken vineyards.
“The introduction of unhealthy vines into an area with the carrier can provoke an epidemic” the FAO says in a statement 17 February. It points to Burgundy where 11.7 hectares of vines had to be removed in 2012 due to infected plants in the area.
Once the disease takes hold it can only be eradicated by uprooting the vines, managing nurseries and insecticide control of “vectors” where the disease might spread, according to France’s research centre Inra.
More than half of French vineyards are subject to compulsory controls now for flavescence dorée, says Inra.
The cicadelle Scaphoideus titanus, a leafhopper that carries the disease, was captured in a Fully, Valais vineyard in 2013 as part of surveillance work done by the cantonal viticulture office working with a team from the Agroscope federal research office.
Swiss stepped up surveillance in 2012
France requires vineyards to check for the disease. The French outbreak in 2012 prompted the Swiss FAO to start a national campaign to check vines. Evidence of the leafhopper was found in canton Vaud and in the Chablais area of Vaud and Valais, as well as in Ticino and Geneva in 2012, but not in other parts of Switzerland. The 2013 summer surveillance campaign focused on French-speaking Switzerland as a result: 57 vine parcels in 40 communes were checked between mid-July and early September.
The leafhopper was found last summer in Mont-sur-Rolle and Aubonne and for the first time a few were spotted in canton Valais in Fully, Sion and Sierre.
Flavescence dorée is a a highly contagious quarantine disease that requires insecticides to be used in vineyards that are affected but also in a larger “vector” where the insect can spread it. The leafhopper’s impact on vines is negligible, says the FAO, in the absence of the disease, but the arrival of the leafhopper calls for extreme diligence now.
French researchers at Sophia-Antipolis near Lyons have been working on an organic solution to fight the disease, but so far with little success, says Inra.
“Treatment measures are compulsory, polluting, costly and run counter to wine industry moves to reduce pesticide use. Compulsory control measures also represent an enormous problem for organic wine grape growers and for wineries in the process of converting to organic agriculture.
Consequently, it is essential in the short term to find methods to better control flavescence dorée and to develop treatment alternatives that use less insecticide. To do so, a better understanding is needed of the pathogen, the vector and the mechanisms that govern interaction between phytoplasma, leafhopper and grapevine.”
How the disease spreads
Inra provides an explanation, based on France’s long years of fighting the disease and what researchers have learned:
“Flavescence dorée is caused by phytoplasma, small bacteria in the Mollicutes class that lack cell walls. Phytoplasmas are intracellular obligate parasites that reproduce in plant phloem tissue and in associated phloem-feeding insects. The main phytoplasma vector for flavescence dorée is the leafhopper Scaphoideus titanus. By feeding on an infected plant and then feeding on other plants, the vector spreads the disease through the vineyard, in much the same way as the Anopheles mosquito transmits malaria in humans. Long-distance dissemination is, however, largely the result of the transport of infected propagative material by humans.”
[…] the Swiss federal agriculture office said that the leafhoppers, Scaphoideus titanus, have now been spotted as far into Switzerland as the centre of canton Valais, from Fully to Sierre. The insects were long thought to be found […]