The decline of syrah

Wines & Vines, Feb, 2002 by Denis Boubals

On January 28, 2000, a meeting of the National Committee on the decline of Syrah in French vineyards was held at ENTAV, Domaine de l'Espiguette au Grau du Roi (30).

Mr. R. Boldron, Director of ENTAV, greeted the 50 participants.

He stressed the importance of Syrah in several French winegrowing regions. Many grapegrowers are complaining about the premature and gradual death of some vines on parcels where this variety is grown. He also emphasized the need for increasing the research on the cause of this decline.

Funds will have to be found (quickly) to carry out research projects.

Mr. Serge Grenan, a researcher at ENTAV, led the discussion that took place after the meeting. He started with a review of the decline and his study of it.

Following the major introduction of Syrah among the vineyard varieties of Southern France, the decline of the vines on Syrah parcels has weighed more and more heavily on growers and technicians.

The first technical meeting on this decline was held in Valence in 1996.

The first studies were conducted by ENTAV.

Another meeting was held in 1997 to develop a questionnaire on the infected parcels.

In 1999, the results of the survey were studied, but the conclusions drawn from them were disappointing.

In 2000, a national committee on the decline of Syrah was formed.

The Symptoms of the Decline of Syrah

Mr. Grenan then gave a detailed description of the symptoms of the decline of Syrah illustrated with slides.

In the spring, we see that branches of the infected vines display leaves with a lighter green that sometimes turn yellow.

Then, as they ripen, the leaves of the infected vines turn red (Figures 1 and 2. See page 46).

At the base of the trunk of the vines, we see swellings that turn into fissured crevices (Figures 3, 4 and 5).

Infection of Syrah appears on different kinds of soils.

Vines with red foliage can be seen on 3-year-old vines.

The crevices that appear at the base of the graft also exhibit necrotic areas.

The infected vines end up dying at the level of the graft, but the rootstock, nevertheless, remains alive and can grow again.

Faced with this incident, most growers replace the dead vines and sometimes re-graft the rootstock.

Finally, some of them use layers (runners).

This decline of the vine affects only Syrah.

It seems the infected vines are not isolated from one another but grouped. Often the decline advances by rows.

This decline began to be noticed among Syrah in 1993. In 1995, it appeared, seriously, in Herault and Gard. In 1997, it appeared in Aude, the eastern Pyrenees and Vaucluse.

In 1998, it manifested itself seriously in the Aubenas area in Ardeche.

The Gaillac and Fronton areas in Southwestern France have been hit but with less serious damage. We saw the first infected vine in Gaillac in 1995; at present, there are 10 parcels there and two in Fronton that are infected.

In areas near Toulouse, we find decline on water-stressed parcels. There is no problem on soils. The vines begin to decline when they are 3 to 4 years old, after which there are vines that die.

It is very strange to note that in Drome and Rhone, where Syrah has been intensively cultivated for a long time, the decline is practically nonexistent. Mr. Garnier of the Drome Chamber of Agriculture has not seen it in Montelimar, nor more in St. Joseph than in the county of Rhone.

No damage has been noted in Tain l'Hermitage, the cradle of Syrah. Some technicians present at the meeting indicated that they are running into decline problems with the Mourvedre, but caution must be exercised. For this variety other factors may be involved, such as overcropping of the vines and a deficiency of potassium.

Studies Conducted to Determine the Cause of the Decline of Syrah

(1) Viruses

Mr. Grenan indicated that he had conducted many tests at ENTAV and in Colmar (INRA) on vines with or without decline symptoms.

With tobacco, a mosaic of chlorotic spots appeared during a transmission test (INRA, Colmar).

We do not know this virus, nor whether it is a virus. It is desirable to pursue these studies.

(2) Implication of the grafting techniques and the hormone treatments used for the production of benchgrafts

Two tests were conducted, utilizing the Omega graft, the English graft, the Green graft and field-budding.

At the same time, the following treatments were applied to the Omega and the English benchgrafts: grafting wax without hormone; grafting wax with hormone; hormone dose 1:2% exuberone; and hormone dose 2:4% exuberone.

This test consists of 10 repetitions of 10 vines for each treatment.

The benchgrafts were planted at Moussac, in the Gard and at St. Mathieu de Treviers in the Herault.

In the third year:

--at Moussac: there are no abnormal symptoms on the vines.

--at St. Mathieu in 1999 there were three vines with red leaves: one Omega graft with grafting wax without hormone; one Omega graft with hormone dose 1:2% exuberone; and one Omega graft with hormone dose 2:4% exuberone.

This test is to be followed up to observe the results in the future.

(3) Water stress