Grapevine flavescence dorée symptoms © Sandrine Eveillard

Grapevine flavescence dorée

The insect vector 

The American grapevine leafhopper, Scaphoideus titanus, is the primary vector of flavescence dorée. INRA researchers have identified several elements of the insect’s behaviour. In particular, hatching is regulated by winter temperatures. This can be used to better anticipate larvae control. Researchers also found that the leafhoppers are attracted to the yellow colour of leaves infected by flavescence dorée, which encourages the spread of the disease.

By Pascale Mollier - Julien Chuche - Denis Thiéry - Daciana Papura - Sylvie Malembic - Alain Blanchard - Xavier Foissac, translated by Daniel McKinnon
Updated on 09/06/2016
Published on 03/26/2013

Flavescence dorée is a disease transmitted by a sucking insect, the grapevine leafhopper. © INRA, Anne-Sophie Walker
Flavescence dorée is a disease transmitted by a sucking insect, the grapevine leafhopper © INRA, Anne-Sophie Walker

The primary vector of flavescence dorée phytoplasma is the leafhopper, Scaphoideus titanus, a sucking insect that spreads the disease by feeding on an infected plant and then feeding on another plant that it injects with infected saliva prior to withdrawing nutrients.

Scaphoideus titanus in Europe is found primarily on the single species of cultivated grapevine, Vitis vinifera

Distribution map of the leafhopper Scaphoideus titanus in Europe © J. Chuche
Distribution map of the leafhopper Scaphoideus titanus in Europe © J. Chuche

Insect lifecycle

There is a single generation per year. Eggs are laid at the end of the summer in the bark of grapevine wood that is more than one year old and then diapause over the winter. Hatching begins at the end of spring.

 There are five larval instars that develop over a period of 35 to 55 days. The first adults generally appear at the end of July and live for approximately one month.

Cycle of the leafhopper Scaphoideus titanus, insect vector of flavescence dorée © J. Chuche
Cycle of the leafhopper Scaphoideus titanus, insect vector of flavescence dorée © J. Chuche

The importance of winter temperatures

Recent studies carried out in Bordeaux demonstrate that cold winter temperatures are not essential for terminating diapause although they do affect male–female ratios over time. The studies also showed that winter temperatures regulate hatching dynamics.

These findings are very important because first hatchings can now be forecast and can be used to better control larvae before they have the chance to acquire the phytoplasma. The findings also allow the ability of the vector to colonise new wine-growing areas to be predicted.

The insect sees yellow

Like many other plant-eating insects, sucking insects in particular, S. titanus displays a strong attraction to the colour yellow. It appears that the attraction is associated with young, developing leaves that are richer in nitrogen and thus of greater potential nutritional value for the insect. S. titanus is attracted by the colour green to a lesser, but still significant, extent. Yellow and, to a larger degree, green are precisely the colours most present on grapevines. The insect’s attraction to these colours is crucial for the propagation of flavescence dorée. Insects are more attracted to the yellowed leaves of white varietals infected with flavescence dorée, thereby spurring a vicious cycle.

Choice tests carried out with the white varietal Baco 22A – a widely planted variety in Armagnac that is highly susceptible to flavescence dorée – confirmed that plants infected with flavescence dorée attract more S. titanus, both at larval and adult stages. The attractiveness of infected plants may in part serve to explain the rapid spread of the disease.

References

- Chuche, J. and Thiéry, D. 2009. Cold winter temperatures condition the egg hatching dynamics of a grape disease vector. Naturwissenschaften, 96: 827-834. 

- Chuche J. 2010. Comportement de Scaphoideus titanus, conséquences spatiales et démographiques, Doctoral thesis, Université Bordeaux 2, 216 p.

- Chuche, J. and Thiéry, D. 2012. Egg incubation temperature differently affects female and male hatching dynamics and larval fitness in a leafhopper. Ecology and Evolution. 2: 732-739.