The decline of syrah
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
A test was conducted by the ENSAM and ENTAV departments of Viticulture using Syrah vines Omega grafted on S04 and planted in pots. These vines were submitted to a variable water stress until now, and following a year of observation, they have not shown any signs of decline.
(4) Mapping the decline
(a) Objectives:
The infected vines have been mapped.
–To determine how the decline is propagated.
–To eventually find a vector.
(b) Controls made with regard to vines
Two hundred vines (4 x 50 vines), arranged by parcel, were mapped. The control systems were complex, ranging up to 20 methods greatly influenced by the individual control.
Since 1999, the control system has been simplified (Table 1.)
The date of observation of the decline symptoms is of great importance. Furthermore, the reddening is more or less early depending on the year.
(c) Partial assessment
–Temporal evolution. The rate of advance varies depending on the parcel under consideration: from fast to slow.
–Spatial evolution. Proximity has an effect: vines recently infected are located near an already dead vine.
The parcel’s path of erosion produces an effect that is always preferential. The course of the water produces an effect on the parcel.
And finally, there is the effect of the soil when the parcel is composed of several different soils; there are spots where the signs of decline are more pronounced.
Neither Syrah clones, system of training, type of grafting nor rootstocks produce any effect. There is a test of several rootstocks being conducted at Chateauneuf de Gadagne (Vaucluse) in which no marked differences appear. This test is worth following.
–Evolution of the different stages of the disease.
The number of A0 vines tends to decrease.
The number of Al vines is relatively stable.
The number of B0 vines tends to increase.
The proportion of B1 vines varies from 3% to 5% in most of the parcels mapped, but on seriously infected parcels it may be as high from 20% to 25%.
The number of SM vines increases.
–Recommendations for future controls in the mapping of decline.
Abandon overly infected parcels; taking into account all the vines in a parcel enables us to ascertain the effects visible on the scale of the parcel in question, not that of a small group of 200 vines.
–Comments of those who mapped the decline.
In Herault, we clearly saw a superposition of dead vines on erosion ravines. In Vaucluse, we noted that abnormal symptoms at the graft area precede reddening of the foliage and the death of the vine. In Gard, on 3-year-old vines, we saw cases of rapid change and others of slow change.
A case was cited of a parcel of Syrah field budded onto Riparia, Paulsen and S04 without any declining vines. On the other hand, there is a 25-year-old parcel at Orgnac, field budded, that has dying vines.
(5) Other avenues of research
a) Bacteria
The LNVP Laboratory in Angers has made several attempts to isolate bacteria using samples it received in September and October without success. To successfully isolate them, the laboratory is asking for samples taken in June and July, which is to be done this year (2000). For the time being, there is no basis for the bacteria hypothesis since not enough of them have been found in the samples that were analyzed.
(b) Parasitic fungi in the wood
Mrs. Dubos at INRA in Bordeaux and J.P. Peros at INRA in Montpellier reported on their observations of Syrah decline.
J.P. Peros analyzed eight vines that revealed a necrosis of the wood growing out of the crevices at the graft area. He found fungi on the front of the necrosis. The fungi he found are a sp Sphaeropsis (or Botryosphaeria). Phaeroacremonium chlamydosporum, Gliocladium roseum, Phaeroacremonium aleophilum and Eutypa lata.
Therefore, the fungi involved in other cases of decline are present.
The crevises constitute important entryways.
We may wonder what role the endophytic Phaeroacremonia play.
In Bordeaux, INRA has isolated the following fungi in the grafting area of declining Syrah vines that came from Vaucluse: Botrytyosphaeria obtusa, the most common; Verticilium cephalosporium; Phomopsis viticola; and Botryosphaeria dothidea.
A Syrah sample from Nimes exhibited Botryosphaeria obtusa, as did a Syrah sample from Perpignan, where Botryosphaeria obtusa was the only fungus isolated.
Infections of cuttings were produced and they observed necroses caused by this fungus, which may be considered to be pathogenic.
Botryosphaeria obtusa has been reported in Hungary and in Portugal. In South America there is a species of Botryosphaeria that is reputed to produce symptoms on the vine of the same type as those of Eutypa lata.
If parasitic fungi in the wood are the cause of the decline, we might consider that disinfecting of the base of the trunk with Bordeaux mixture or sodium arsenite could afford some protection. In any case it is worth trying.
(6) New research projects to be undertaken
–Transmission of symptoms by grafts from infected vines from the bottom up and from the top down on rootstocks, Syrah and other varieties of Vitis vinifera, Cabernet Sauvignon, Pinot, Durif, Dureza and Grenache.
We will also conduct a study of eventual transmission (of symptoms) by rootstock regrowths taken from a dead vine. This line of research will be conducted at ENTAV.
–Histological studies of grafts with the kinetics of callogenesis.
An initial study will focus on Syrah grafted onto 140 Ruggieri dipped in nonhormonal wax or hormonal wax in two doses applied at the top and bottom of the graft. Observations will be carried out when (the plants) come out of stratification in the nursery and when they are planted.
The behavior of the cambium and the period during which the place where the crevices begin to appear will, in particular, be studied. Furthermore, sections for a histological study will be cut at the graft area of a declining Syrah vine.
And lastly, the possibility has been raised of exploring genome study leads in an attempt to explain the specificity of the phenomenon linked with the Syrah variety.
Conclusion
So, a major research effort on the decline of Syrah is in progress.
We can draw grapegrower attention to two points: nurserymen are not the cause of this problem; and those grapegrowers who plant Syrah should avoid having overly vigorous vines and over-cropping them the first few years.
(This article was translated from Progres Agricole et Vinicole, 2000, 117, #6, by Gab MacLean of Gab MacLean Nursery, Inc.)
Table 1
New Notation for Syrah Decline
VEGETATION
NORMAL WEAKENING DEAD, MISSING OR
REDDENING REPLACED VINE
JOINT AREA 0 1
Normal or bulging A0 A1 SM
without crevices
A
Bulging with B0 B1
crevices
B
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