Agroecological protection to control Esca, a grapevine trunk disease – WinEsca

Viticulture has a major role in French agriculture and, with a positive trade balance of 14.2 billion euros (in 2021), its contribution to the economy is undoubtedly considerable. Regarding the emblematic sector of Cognac, it was the leader of the French of wines and spirits exports (3.6 billion euros in sales) in 2021. Hennessy, the world Cognac sales leader exports around 98% of its products. The company, present on all continents, is also historically deeply rooted in the Charente vineyards.

This 89,560 ha vineyard is dedicated to producing eau-de-vie de Cognac. This vineyard has its specifications, which require vigorous plants and a minimum number of unproductive vines, to produce high-quality Cognac. The deleterious action of Esca, a Grapevine Trunk Disease (GTD), by attacking at least 18% of the Cognac vineyard, jeopardizes this objective of quality plants. Esca can decrease vineyard longevity, and affect berry and wine qualities not only in France but also throughout the world. For 2014-2017 alone, the estimated losses are huge: nearly 12% of French vineyards are unproductive due to GTDs, mainly Esca, causing one billion euros in shortfall. It is, therefore, one of the key elements of French agriculture and cultural heritage that is being put at risk.

This situation endangers the French viticulture sector’s development prospects for the coming years, seriously compromising Hennessy’s initial projections. Driven by its international dimension and fully assuming its leadership role in the viticulture sector,
Hennessy has chosen to work with scientists from IPREM (CNRS / University of Pau and Pays de l'Adour-E2S) involved in research to fight against Esca in order to apply for the Industrial Chair program of the ANR. GreenCell, one of the French leaders in microbial ecology and industrial fermentation, has joined the partners of this chair to develop biocontrol products. The production and transformation of micro-organisms to protect or stimulate plant growth is indeed one of the strengths of GreenCell.
A first Industrial Chair, GTDfree, provided useful results and opened up new perspectives to control Esca. The WinEsca project is therefore the result of a fruitful collaboration between Maison Hennessy, GreenCell, scientists from IPREM and other research units and winegrower partners of the industrial group. Research results will benefit not only the Cognac viticulture sector but also the French and international vineyards.

The WinEsca project aims to control Esca by focusing on key points. (i) limiting the development of wood necrosis, by applying a pruning method to plants of different ages (at plantation, in young and mature grapevines). The physiology, including sap flows, and the evolution of the microflora in connection with the early appearance of wood necrosis will be particularly monitored. (ii) Biocontrol agents will be applied at plantation to provide preventive protection. Mature grapevines affected by Esca will also be treated by targeting the white-rot necrosis, which is typical of this disease. For this, bacteria that inhibit the overabundant pathogenic fungus of white-rot, Fomitiporia mediterranea, will be introduced into this necrosis. (iii) Assess the economic aspect of the proposed solutions and the benefits that winegrowers can derive from them. The societal acceptance of biocontrol, i.e. by winegrowers and consumers, will also be studied.
Finally, the WinEsca strategy, based on the management of complementary control approaches to preserve healthy grapevines and cure Esca-diseased plants, is designed to be a pivotal project; one that offers viticulturists relevant methods for controlling Esca that are fully adapted to environmentally-friendly viticulture.