Technical Yearbook 2024

1 100 ha of vineyard were impacted by the flood of late September 2023. Out of this number, almost 100% is wine grapes (compared to table or drying grapes), with Colombar representing about 70%. For crop estimation purposes, a 50% damage loss was allocated to the affected blocks, and at the time of writing this article in March 2024, this estimate reflected a good indication of the actual crop. The effect on the 2025 crop From October 2023 to April 2024 the potential 2025 crop’s flower clusters already initiated, divided and elongated within the dormant primary buds. In the case of vineyards that were under water, this important process would certainly have been affected. There is particular concern over the nearly 20% of blocks that were submerged the longest (more than three days), and this is where the biggest potential crop losses for 2025 are expected. Lessons learnt for the future During the 2023/24 season the resilience and adaptability of grapevines were once again proven by the fact that no total crop losses materialised due to flooding. Producers who have the land available, can consider replacing the lower-lying high-risk blocks closest to the river banks with higher-lying blocks over time. There are already producers who are following this practice. The manipulation of budding dates by means of dormancy-breaking agents and pruning time adjustments is not a practical solution, because the river can overflow its walls at any time from June to December, and there is no way to predict this. In order to distribute risk, a portion of the lower-lying vineyards can be pruned early and another portion very late, at the end of September/early October. It is important to do a damage estimation for cellars and producers as soon as possible after such a flooding event, for planning and budgeting purposes. Resources like digital farm maps, new aerial photos and multispectral images make it possible to access correct information very quickly, enabling more accurate damage estimates. If the wet soils are inaccessible for tractor traffic, producers can use alternative spraying methods to execute early and timely fungal control. 

Poor flowering and set of clusters that survived the flooding.

Blocks that were submerged for 24 hours or less, immediately developed young leaves and new growing tips.

Reference https://www.wineland.co.za/vineyard-response-to-the-floods-in-the-olifants-river-region-during-2023/

For more information, contact Gert Engelbrecht at gerte@vinpro.co.za.

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TECHNICAL YEARBOOK 2024