The dreaded plague that devastated Europe in the 19th century now reaches the Canary Islands.

The evils caused by phylloxera, a feared insect parasite of the vine, seemed like a story of times gone by. At the end of the 19th century, its advance brought down the European wine sector, but even today the formula that was found to keep it at bay is fully valid: instead of planting the vines with Vitis vinifera –European vine suitable for making wine– directly on the ground –on a free rootstock–, they are grafted onto American rootstock –roots of non-productive American vineyards– which prevents insect attacks from being fatal.

In the Canary Islands, phylloxera had previously been kept out of reach without resorting to rootstock, which has allowed vineyards to maintain even bicentennial vineyards and unique pre-phylloxera varieties, but they are no longer an exception. On July 30, the first positive case of phylloxera was reported in a vine in Valle de Guerra, in the municipality of La Laguna in northern Tenerife. Since then, 5,289 surveys have been carried out on the same island and 84 infected vines have been found, the majority in the Tacoronte-Acentejo Designation of Origin (DO). Vines have also been detected in the DO Valle de La Orotava and, as confirmed this Thursday, also in the DO Valle de Güimar in the south of the island.

The Deputy Minister of the Primary Sector of the Canary Islands, Eduardo García, tells ARA that phylloxera has basically been detected in plots in a state of abandonment or semi-abandonment, not intended for professional cultivation, and that they are trying to put an end to the plague: "We must eradicate it by all means so that it does not spread. A mixture of insecticide and herbicide is applied to the affected vines, they are uprooted and a mesh is placed so that they do not sprout again. In addition, strong restrictions have been ordered on the movement of grapes and plant material, updated information is offered - such as, with the websites https://filoxera.es/ and https://visorfiloxera.sitcan.es/–, a scientific-technical committee has been created and a strategic plan is being worked on to guarantee the future of Canarian viticulture.

At its roots it is devastating

The impact of phylloxera on the Canary Islands is still uncertain, but it could be significant: today's Canary Island vines are planted like those from the 19th century that failed to withstand the plague, without grafting onto American rootstocks, because the area was considered phylloxera-free. The hope now is that the insect will not spread from the leaves—the galicolous form of phylloxera, which is the only one detected so far in Tenerife, according to García—to the roots—the radiculous form, which is devastating—but experts assume this will happen.

It used to be said that the Canary Islands didn't have phylloxera because they are isolated and have volcanic soils, but they are neither isolated from the rest of the world nor are their volcanic soils entirely sandy, which is what makes life difficult for phylloxera. For José Ramón Lissarrague, consultant and professor of viticulture at the Polytechnic University of Madrid (UPM), the insect "most likely arrived on plant material that was introduced in an inopportune manner," a statement echoed by Maria Francesca Fort Marsal, a professor in the Department of Biochemistry and Biotechnology at the Rovira i Virgili University and an expert on Canary Island varieties, who believes it must have arrived "in the form of a winter egg."

Phylloxera has "a very complex biology," agree Lissarrague and Fort. It can reproduce sexually or asexually (parthenogenesis), so a single female may have already paved the way with a first clutch of hundreds of eggs, and the wind may facilitate its spread. On the leaves, the activity of this insect is not fatal to the vineyard, but on the roots, it is: European vines not grafted onto American rootstock are unable to quickly heal the wounds caused by the insect's sap-sucking behavior, and the roots of the vine end up rotting. Fort has predicted the evolution of phylloxera in Tenerife, based on the hypothesis that it must have entered the winter dormancy period in early 2025, and has no doubt that it is already affecting the roots: "The root-growing phase must have definitely taken hold."

How far will the crisis go?

In the Tacoronte-Acentejo DO, the first appellation created in the Canary Islands in 1992, the most widely planted varieties are Listán tinta (red), blanca (white), and negro (black). Here, they have seen how phylloxera has added to the massive crisis linked to climate change already affecting this Tenerife region. According to the DO's manager, María de la Paz Gil, the arrival of phylloxera has been "a major surprise at all levels," just as the severe drought and lack of winters—temperatures rarely drop below 20 degrees—have left a situation that is shocking in the 20 years since the beginning of the 680s, from 30 to 22 wineries, and harvests of 1.2 million kilos in one year, tending toward just shy of 400,000 kilos this year.

The future of Canarian viticulture now depends on the ability to prevent a repeat of the devastation caused by phylloxera in the 19th century and to adapt to climate change. Gil calls for "an aggressive agricultural policy" that addresses issues such as water shortages and containing phylloxera to prevent it from spreading to productive vineyards at wineries that are already struggling. Replanting vineyards with rootstocks is already on the table. Gil is only considering this option experimentally, although he admits it cannot be ruled out either, while the experts consulted believe it will be inevitable.

"In every part of the world where phylloxera appeared, it ended up spreading, and the only way to guarantee the survival of the vineyard in every sense is to graft with the American rootstock," says Lissarrague, and Fort agrees: "In Tenerife, I'm quite clear that they will have to reconvert the vineyards," a generation that will help mitigate the effects of climate change and thus prevent the loss of local grape varieties. With the worldwide recognition that Canarian wines have achieved in the last 20 years, Deputy Minister García hopes that his raw material will not be lost now: "We have managed to maintain a germplasm—local varieties—that we must defend."

Many unknowns remain to be resolved. Whether avocados could also be affected by phylloxera or whether it will be prevented from reaching other islands. "There are vineyards that are too old for them to suddenly tell you they have to uproot everything," considers winemaker Elisa Ludeña of the El Grifo winery in Lanzarote, which grows even two-hundred-year-old vines. She believes it should be carefully studied whether to resort to rootstocks: "Are the vines resistant to the pest?" For now, history has shown that European vines are not resistant to rootstocks on their own.