Vertical vegetal endotherapy: a new mode of treatment to cure grapevine trunk diseases?
Résumé
Esca is usually described as one of the most devastating grapevine trunk diseases. This disease has been increasing in the last 30 years, and since sodium arsenite was banned in 2001, there is no solution available to effectively cure the disease. One potential technique could be plant endotherapy, which is used in fruit tree cultivation and in urban landscape trees. It has many advantages, particularly in terms of the environment as, compared to spraying, it allows a low input as for treatment doses and limits product drift in soil, air and water. This technique of vegetal endotherapy consists of drilling and injecting chemicals compounds or beneficial microorganisms directly into the plant. It has many advantages, particularly for the environment. Indeed, compared to a conventional spray, this technique allows a reduction in treatment doses and limits product drift into the soil, air and water, thus reducing the impact on non-target organisms. Recently, it has been reported that the impacts of Esca could be minimized by mechanical curettage of the white rot. The recent study of the mechanisms of sodium arsenite showed that the molecule is concentrated in white rot after spray application to the wood. All of these results suggest that some fungal activity in the white rot may have a role in Esca symptoms, specifically leaf symptoms. We adapted plant endotherapy to grapevine by drilling a hole vertically in the trunk to reach and treat directly the white rot, with chemical compounds at different concentrations, and therefore the pathogens associated to it. We apply a “chemical curettage” to vines with leaf and wood symptoms of Esca. Experiments initiated in an Alsace vineyard in 2018, showed a fairly promising trend with a reduction in the expression of leaf symptoms by up to 50% in some varieties (V. vinifera cv Gewurztraminer and Riesling) treated by this method. The experiments need to be repeated, monitored and extended on other regions, over several years, to see if this trend is confirmed and if this method could be used to reduce the impact of Esca.