Vine pruning
The curettage of the vine is a technique often used to limit the effects of grapevine trunk diseases. Grapevine trunk diseases, such as Esca, Black Dead Arm, and Eutypa dieback, are a major cause of decline in the European vineyard and could lead to the disappearance of many vines in the medium and long term.
This technique consists of removing the wood damaged by white rot (called "amadou") to preserve the functional wood and sap flow. On the vine, amadou is mainly caused by saprophytic fungi, but also by some pathogenic species capable of attacking living tissues.
Curettage, first experimented in France and then in Italy, is based on a practice known since Antiquity to manage plants affected by Esca. According to Poussard, who used this technique at the end of the 1800s, trunk cleaning showed a success rate of 90 to 95% when applied to Esca.
Conditions for applying this technique
- The limit of curettage is the plant's recovery capacity, meaning that vines must not be too damaged by white rot or too weak.
- It is recommended to apply it on plants for which the symptoms of grapevine trunk diseases are mild.
- This technique can be applied to old vines affected by Esca.
- Curettage is not effective against apoplexy.
- Young vineyards show better recovery results than old ones.
- This technique can be performed on vines affected by Esca or Black Dead Arm but curettage shows no effectiveness against Eutypa dieback.
- Trunk curettage can be done at any time of the year. However, the winter period is more convenient. In this case, symptomatic vines of grapevine trunk diseases must be identified and marked during summer (the month of September is most appropriate to see Esca symptoms). If curettage is done in summer, the harvest can be saved and the vine can lignify normally.
- Trunk cleaning can occur as soon as the first symptoms appear, when leaves dry out between June and September. If done in June, curettage allows saving the current year's harvest.
Implementation
Curettage mainly consists of digging into the trunk to remove the diseased parts of the vine, often located near dead wood areas or inside pruning wounds.
Steps of curettage
- Identification and marking of symptomatic vines.
- Opening the trunk using a small chainsaw.
- Identification of diseased parts of the trunk, recognizable by their spongy texture (this is the amadou).
- Removal of diseased tissues, scraping with the chainsaw along the vine axis. Be careful not to block sap flow by cutting healthy wood!
Recommendations
- Respect sap flow during pruning.
- Scrape thoroughly to remove all diseased wood.
- If symptoms reappear, a second curettage can be performed the same year.
Results
After vine curettage, disease symptoms disappear. The sanitized vine is more vigorous than non-curetted vines and if the technique is performed as soon as the first symptoms appear (around July), the harvest can be preserved.
Technical and economic data
- Curettage time: 100 to 200 stocks/day, about 5 minutes per stock.
- Estimated cost: €2.5/vine.
- Equipment cost: €1700 for a micro-chainsaw. For more information on curettage equipment, SICAVAC tested for you: Curettage equipment
When diseased vines are uprooted and replaced by new ones, it affects the quality and quantity of grapes produced. Having healthy plants with a long lifespan is a priority for every winemaker as it ensures continuity of quality and the distinctive character of their wines. Curettage also has significant economic consequences for producers as it allows saving replanting costs (uprooting diseased vines, digging holes, planting vines, training the stock) and does not cause a production gap in the years following planting of new plants.
Practical cases of curettage
Curettage in the Southwest
Here is the example of a winemaker from the Saint-Mont region in the department of Gers: Trunk cleaning has been carried out since 2014 on a plot of Cabernet Sauvignon affected by Esca and Black Dead Arm.
- Diseased stocks are identified and marked in September, before harvest.
- After harvest, the vine is cut vertically with a small chainsaw to open the trunk. Once opened, amadou is located and removed with the chainsaw. If amadou is not completely removed, a second trunk cleaning can be performed. Trunk cleaning also helps identify pruning errors, see dead tissues and sap flows, and helps the winemaker better understand pruning respecting sap flow. According to this winemaker, curettage takes about 5 minutes per stock.
Estimated results
According to the winemaker, 90% of curetted vines survive and no longer show symptoms.
Curettage in Italy
A small chainsaw is used to open the trunk and remove parts affected by Esca, leaving only lateral parts to allow sap circulation. Then, with a smaller saw, degraded wood under drying cones is cleaned. This experience, although limited, shows that after this operation more than 80% of plants did not show new symptoms. The plant is then detoxified, strengthened, and can produce at full capacity.
Estimated results
Recent trials, conducted by an Italian company, yielded promising results, with 97% asymptomatic plants after one year. In 6 years, 10,000 plants have been treated in Italy and France. The results are astonishing: 90% of plants subjected to curettage returned to full productivity.
Sources
- This article was written based on the PDF document: "Curettage: A practice applied in vineyards to limit the expression of grapevine trunk disease symptoms" published within the framework of the National Vineyard Decline Plan.
- TechniLoire, How to manage curettage of vines affected by trunk diseases?
