A few centuries ago—and we don’t have to look very far—poor young women were burned in village squares for witchcraft, all due to foolish superstitions and unfounded beliefs.
By Julio Prieto Díaz. Agricultural Engineer & Oenologist, and Viticulture Consultant
Those poor girls may have simply used herbs for healing, or even more bizarrely, if something bad happened while they were passing down the street, they were blamed for casting some evil spell.
Yes, you might laugh at this, but in viticulture we are still dragging along many myths and false beliefs that lead us to lose harvests or to be far less efficient than we could be.
Every year there is some event that marks us at a productive level and causes us to lose crops or incur excessive costs.
In a sector where profitability—under low product prices—depends on being highly efficient, we cannot afford to stop increasing our capacity to control processes.
This year, downy mildew will appear in your vineyard—and no, it won’t be by magic, nor because you had mildew last year.
The appearance of downy mildew depends largely on the overwintering conditions of the fungus—that is, on how the oospores survive autumn and winter.
Mild temperatures and many days of humidity worsen the situation. This means that as soon as spring arrives and conditions suitable for infection occur, it will happen—and with particular virulence.
If you also add a large amount of inoculum remaining in the soil from the previous year, the infection will be even more severe.
So we are heading into another difficult year if you are unable to establish risk levels and, accordingly, a different treatment strategy.
Later, we can blame plant protection products for not being what they used to be, or climate change—but the reality is that you were caught with your trousers down and were not ready for what was coming.
Cluster affected by the disease
We generally don’t treat properly—this is a statement I can say applies to 80% of vineyards: machines that do not distribute the product correctly, that are not properly adjusted, that do not work at the right pressure or with the appropriate droplet size. As a result, application outcomes are mediocre, or at best inefficient.
We pass between the vines, yes—but we don’t treat well, and then the problems begin.
This happens with downy mildew, but the same applies when a difficult year for powdery mildew arrives, or when leafhopper populations suddenly explode and we don’t know why or where they came from.
Everything points to this year bringing a lot of vegetative growth in the vineyard during spring. I don’t know if there will be a lot of grapes—that will depend on the area—but yes, a lot of vegetation, and that will complicate sanitary management. We need to be very precise, understand the risks, know when and where to treat and monitor, and also control the quality of applications.
Whether there will be a lot of grapes depends on how the summer went, what reserves were built up in autumn, and how the harvest was programmed.
You may not know it, but your harvest is already programmed in your vineyards, even though they have not yet budded. Vines that had a good summer and recovered well after harvest will have good productive potential; those that suffered a severe leafhopper attack most likely will not. Neither will those that endured an agonizing summer.
Leaf with symptoms
The problem is not treating—it is knowing when to treat. Detecting risk in time is key; once downy mildew is visible, it is already too late.
This is what viticulture is about: understanding processes, even those we think are most trivial, such as running a cultivator through the soil.
We must connect risk, timing and the quality of actions. It’s not about spending more—it’s about spending better, and especially on what has the greatest impact on your operation.
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