How to fight Esca, the scourge of vineyards?

The grapevine is that marvelous vine that offers us, with each harvest, the pleasure of tasting and the surprise of expert craftsmanship. A marvelous plant indeed, but the grapevine is fragile. Subject to quite a few adverse weather conditions (which we've been discussing endlessly this year), the grapevine can also, like any living organism, fall ill. There are dozens and dozens of diseases that can affect the grapevine, such as esca, which has unfortunately returned to our vineyards in recent years! 3, 2, 1, Description and treatment!

Kesako l'esca

No, Esca isn't the latest trendy business school as one might think (ahem), but one of the oldest, if not the oldest, diseases of the vine: quite simply, a fungal disease that causes the vine to collapse! To explain: basically, it means that fungi take hold in the vine. It's a disease that enters through the wood, causing degradation, even complete dieback; it's a form of necrosis of the spine of our sacred plant…

Several fungi attack the vines. There are three main ones, originating from Greco-Roman times! Yes, they are tenacious, and like all fungi, they thrive in humid conditions and flourish in hot weather. Yum! They certainly grow, but where do they find the entry point to establish themselves? Well, most often, contamination occurs through large pruning wounds made by the winegrower during a winter that was a little too mild and a little too rainy. From there, the fungi take up residence in the wound and develop throughout the year.

NB: I'm putting the names of these mushrooms for those who are interested: Phaemoniella Chlamydospora / Phaeocremonium aleophilum / Famitiporia (the one responsible for tinder... don't worry, we'll talk about it later).

Recognize the esca

With a cold, you have a stuffy nose, difficulty breathing, etc. With Esca, it's the same, symptoms are observable quite quickly, first on the leaves, then on the wood.

• On the leaves: Once the fungi reach the base of the vine, they block the flow of sap (the vine's lifeblood) which is supposed to reach the tips of the leaves to make the vine fruitful. These leaves then change color (yellow on white grape varieties, red on red grape varieties) before finally drying out completely. This can sometimes take a few hours; it's very rapid—it's apoplexy!
• Regarding the wood: You were wondering what tinder fungus could possibly do earlier (yes, you were wondering). Tinder fungus is the spongy white rot resulting from the development of the fungus, which causes central or sectoral necrosis of the wood.

Once observed, these symptoms spread very quickly throughout the vine, and the winegrower generally only sees the extent of the damage in their vineyard in August following the infection. In France, one of the most affected regions is the Loire Valley and its Cabernet Franc (4% of the vines there were uprooted in 2012). Savagnin in the Jura is also very susceptible to esca, and so on.

Let's stop tearing things down, let's fight against Esca!

To date, uprooting diseased vines seems to be the only solution for eradicating esca from a vineyard. However, this drastic solution—like the preventative use of sodium arsenite, banned in 2011—is not the only one! Indeed, there are methods for preventing and treating esca, such as wearing a scarf to avoid catching a cold, or taking Fervex to make it disappear.

Regarding prevention, it can be done in three different ways:

• Pruning must be respectful of the vine . This is why in 1921, René Laffond published L'Apoplexie in which he developed a preventive treatment of Esca (and other wood diseases) by the Poussard pruning which allows the return of the sap path in the base of the vine to be positioned.
• Prevention can also be achieved through shoot thinning (an operation that aims to remove non-fruiting shoots, known as "suckers"). Many growers practice manual or mechanical shoot thinning. To avoid creating large pruning wounds, it is recommended to use pruning shears, which allows for greater precision and therefore less damage, preventing necrosis from developing.
• In the future, it would also be good to allow nursery owners to have the necessary means to analyze and sort contaminated wood , something which is unfortunately not currently done due to a lack of resources…
  
  As for the cure, and this is what we wanted to get to, it is good to know that it is possible in two ways, without having to uproot the vine!
  
• A "surgical operation": curettage . This operation aims to remove (cure) the part of the wood contaminated by tinder fungus (yes, you know). This operation is extremely delicate, as it involves using a chainsaw to cut into the wood and remove the fungus, with the risk of cutting off the sap flow that we are trying to save! When curettage is done properly, the vine produces grapes again the following year, and in 99% of cases, the wood heals! (Video below at 5:05)
  
• Because this practice is very delicate, it is not suitable for severely affected, inoperable wood. In such cases, regrafting can be used, as in most instances, esca takes hold on a vine whose rootstock is healthy (since its function is to be resistant to certain diseases). The procedure involves removing the vine from the rootstock, cutting a slit in the latter to insert a new scion! Like any newly planted young vine, the regrafted vine will be able to produce quality grapes as early as two years after regrafting. Even more surprisingly, the grapes it produces will be the same age as the roots of the rootstock! This practice remains effective in 90% of cases; it's worth a try! (Video below at 10:06)

It is, of course, complicated to plan these operations when several hectares of the same vineyard are affected by the disease, as the labor required is extremely significant. Nevertheless, this perspective offers hope for diseased vines, which ultimately do not have only one future: the trash heap. This perspective is also excellently presented by Denis Dubourdieu in a video (below), without which this article would not have been complete. It is with a heartfelt thought for this great oenologist that this article is published, as Denis Dubourdieu passed away on July 26, 2016. This artist of wine shared his knowledge with us, notably contributing to the revival of effective solutions for combating esca.

Source of the documentation:

Video presented by Denis Dubourdieu and the master tailors Simonit&Sirch

Institute of Vine and Wine Sciences

French Institute of Vine and Wine.

Mélany Bachmann (wine merchant)