I was tipped about this interesting story about vine disease and cure by Laurent Saillard who works in the vineyard of Clos Roche Blanche in the Loire.
Esca is a vine disease which is an increasing nuisance in Europe and in France, the hows & whys being still little understood in spite of extensive studies (read this interesting report on esca - pdf). While known already in ancient times, it surged alarmingly in recent years, especially that a chemical previously used to control it (arsenite) was banned a few years ago. Didier Barrouillet of Clos Roche Blanche, who farms organicly in Mareuil-sur-Cher in the Loire region, has been faced with the problem too, but he noticed that the disease was more prevalent in the plots which had received treatments in the past (before he turned the whole vineyard organic in 1992) than in the plots which had never been touched by chemicals. Some of his vineyards qualify as virgin of any systemic chemical treatment, having been planted on land never cultivated before. What is also interesting is that this disease is even more active in the conventionally-farmed vineyards of his colleagues, where systemic chemicals are still used. Didier Barouillet discovered that the surge of this of disease may lie in the destructive effect of the chemicals accumulated in the ground on the bacterial and microbian life of the subsoil, and that its cure has to do with a pro-active revitalization of the sub-soil of the vineyard. Here is the transcription of an interview I had with him while visiting his vineyards.
According to Didier barrouillet, there is a direct relation between the mycorhization rate of the plant roots and Esca. The higher the mycorhization rate in a given vineyard, the lower will be the incidence of esca among its vines. Mycorhization is the fungus activity on the roots of the plants. All the plants need this exchange with fungus at the root level and attract a crowd of these mycetes. All plants, except cruciferous plants like cabbage for example. the mycorhizes along the roots are particularly useful for the plants when there is a lack of phosphorus in the soil because these fungus are the ones who bring phosphorus to the plant in exchange with carbon-hydrats that they are unable to produce by lack of chlorophyll. There is an active, mutually-beneficial relation between the plants and the mycorhizes, the mycetes living along the roots. To confirm his intuition, he made a study from roots taken from a conventionally-farmed vineyard elsewhere (which had a lot of dead vines with esca), using fuchsin baths and found a mycorhization rate of zero. In another plot where esca was less widespread (say, with a pathology proportion like it used to be 25 years ago), the mycorization rate of the roots was 25%. It seemed to show an obvious link between the systemic chemical products, the mycetes density on the roots, and the extent of esca. Asked if he shared his research with someone in the French agro-research bodies (INRA for example), he answers that they're not interested in the origin of the Esca surge and consider him as a lunatic. They eventually look for a cure but don't want to investigate on the root (appropriate term !) of the problem. It's been proved by an INRA study made at least 10 years ago that systemic chemicals are channelled down by the sap and destroy the mycetes along the roots like antibiotics do in the digestive tracks of humans. Now, it's easy to destroy this microbian population, but harder to restore. A damaged soil, he says, needs a lot of time to recover from the chemicals, sometimes a century could be necessary to get rid of the long-life remnants of years of chemical sprayings. This is especially true for the vineyards : in France, lots of copper has been dumped, first, in the early 20th century, the farmers doing their copper mix (bouillie bordelaise) themselves and weren't shy of spraying high doses. A well-managed vineyard, he says had to have blue posts, this proved a generous use of copper... Copper actually doesn't harm mycorhizes but it does cause trouble in other subsoil organisms. But later, more harmful products were sprayed with the same blind generosity, the growers unknowingly destroying their soils year after year.
What made him go through his experiment with bringing mycorhizes with wild leeks was his encounter with a very knowledgeable person in the field, Mr Mario Fregoni, a very old man now, who is a former president of the Office International de la Vigne et du Vin, who told him that the experiment could work. He didn't say that to be kind but really thought it feasible. Mr Fregoni added that it was not possible to just spray exogen mycorhizes in the vineyard because they die after 2 years, as they don't survive the fierce competition with other microbes in the soil.
At this point of the conversation, we arrive in a vineyard plot where he says he has been conducting for 2 years experiments with leeks. He decided to voluntarily re-mycorhize the under-soil of this Sauvignon plot by planting leeks. The interesting thing is that these mycorhizes or mycetes are able to migrate from a root to another : from the leeks' root hair, they can move to the vine's root nearby, and according to him even migrate a few meters from their original home, weaving a mycelian web under the surface. So he planted wild leeks (also called perpetual leeks) along with garden leeks in this plot. He planted in priority near the esca-stricken vines, when the symptoms on the shrinking foliage announce the near-to-come death of the vine. Miracles did happen since he started this experiment, and he saw vines recovering from esca, which he never saw before. He shows one of these vines with a foliage free of symptoms and expanding. He shows another vine that he thought was already dead last year, he had even prepared a marcotage from the next vine to replace it. But the leek planted along it resuscitated it back to life. It still needs time to recover complete normality but is already in good way.
I remember reading a nice post with pictures on the subject by Jim's Loire shortly after having shot this picture, I wondered if telepathy was involved here...