Is Gone Wild Grapevine a dangerous grape cultivation?

Flavescence Dorée is a horrifying Grapevine disease among the Wine Glowers, spreading beyond cultivated vineyards. A joint study by Federal Institute WSL and agroscope published in the Journal of Plant Biology shows that wild grapevine and associated vector insects contribute to spreading forest disease.

Ticino’s Merlot glasses are a treat that many appreciate. However, the grape disease called Flavescence Dorée is causing concern among Ticino’s wineglowers. Flavescencedorée is caused by plant biomas, a bacteria that does not have a cell wall. The cell wall is transmitted to the grapevine by an insect called Scaphoideus Titanus in the American grapevine leaves. There is no cure available for infected plants, so they inevitably die over time.

Forests are also the source of infection

For a long time, disease and its management have been considered purely an agricultural issue and was investigated by agroscope, the Swiss Center for Excellence for Agricultural Research. Researchers later discovered that the neighboring forest played a role. For example, grapevine persists frequently because it is not continuous with the wine grower’s family.

Over time, such abandoned vineyards can turn into forests. Surviving grapes climb forest trees and become potential reservoirs of disease. This is a situation that was not known until recently.

This is why WSL and agroscope began research cooperation in 2016. Researchers collected grapevine leaves and insects from 13 different test sites where grapevine is no longer in the forest. In the laboratory, we tested samples of related plant plasma and compared the genetic properties of the failed grapevine pathogen with the genetic properties of cultivated grapevine.

Control measures for vineyards are not sufficient

The study found that fallen wild grapes were affected by similar infectious diseases as cultivated grapes. Furthermore, the pathogens in wild and cultivated grapes were genetically identical. “This reinforces concerns that forests are also infection reservoirs as American grapevine leaf happers travel between vineyards and forests,” says WSL Project Manager Marco Conedella.

This also explains why previous efforts to control disease by applying insecticides, removing infected grapevine, and using grapevine with certified vineyard pathogens was not sufficient to stop the disease from spreading to vineyards right in the forest.

Another finding of this study was that in addition to the American Grapevine Leaf Happers, other insects such as the non-native oriental leaf hopper oriental horned daphnia, can carry plant formation and potentially transmit disease between forests and vineyards. This further complicates the pathways of disease distribution.

“It’s important to act now,” Conedella emphasizes. Wild grapevine may contribute to spreading to previously unaffected areas of the disease. According to Conedella, “prevention and early detection measures are urgently needed in other wine-growing regions in Switzerland.”

This does not necessarily require insecticides. Certain forms of landscape management, such as the complete removal of Goonewild Grapevine, are extremely effective in preventing further spread of disease.

In the next phase of the project, researchers want to learn more about other insects that play a potential role in pathogen transmission and investigate whether Swiss Wein Glowers is ready for such preventive control measures.

Characteristics of flavesense dough

Plant plasma (Candidatus Phytoplasma vitis) is involved in causing grape flame dre (FD). Therefore, plant plasmas are classified as sequestered organisms of Switzerland and the European Union. This means that suspected cases of FD will be reported to the responsible authority and will have an obligation to control the disease.

FD was first observed in France in the 1950s. In Switzerland, the first infected grapevine was discovered in Ticino in 2004. Since then, the disease has spread to almost every viticulture region south of the Alps and to the Valley, Beau and the cantons of Geneva. The rest of Switzerland is still FD-free.

American grapevine leaf happers transmit the disease by sucking sap from infected grapes, thereby picking up pathogens and passing them on to other grape grapes. In vineyards, individual diseased grapevine can quickly lead to epidemics. Current control measures include the use of insecticides and removal of infected grapes.