The trichogramma put in a check to the chestnut trees of Malaga

Uploaded to your off-road vehicle, Juan Carlos Rubio runs along a dirt road that cuts through an enchanted forest. It is the appearance given by the ancient chestnut trees to the Genal Valley, a region located two hours from Malaga. The farm is located in the payment of Benajarón, in the municipality of Jubrique. Home to about 150 trees, but the farmer goes direct to a dozen of them without just leaves. The few that are preserved are shrunken in on themselves. "It is the clear example of chestnut trees affected by the trichogramma,” he explains. This species, the Drycosmus kuriphilus, came from China to Malaga in 2014 and, since then, has in check to the farmers. “Keep like this, it's going to be a catastrophe,” stresses Rubio.

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The insect measures only 2.5 mm, but are threatened by close to 4,000 hectares of chestnut groves of the Valley of Genal. The area is home to a handful of small towns and for some of these trees are its main economy. The Coordinator of Organizations of Farmers and Stockbreeders (COAG) estimates that there are 1,500 families linked to the production of chestnuts. The sector generates tens of millions of euros a year and produces as an average four millions of pounds annually. The 60% is exported to Italy, Uk, Holland and Belgium.

A volume that this tiny insect can make it disappear. “The chestnut is vital to these peoples, what would happen without him?” asks Miguel Angel Herrera, mayor of Genalguacil, a village of 405 inhabitants two decades ago had 575. The fall of population affects the whole of the valley, which from 2000 to 2017 went from 8.138 to 6.935 inhabitants, according to the INE.

The fear of the trichogramma asian is present even in years like this, when the production of chestnuts has reached a record high of five million pounds. Since the insect went into the ronda, its ravages are increasing exponentially. “We need to control the pest already,” says Francisco Boza, head of the COAG Andalucía. “There are those who have between a 30 and a 50% less of chestnuts a few years ago,” says Matthew Rosado, president of the Cooperative ValGenal, located in Pujerra.

400.000 insects to end the plague

Until now, the best way to fight the plague is with another insect, called the Torymus sinensis and that also comes from China. It is its natural predator. The Junta de Andalucía has been making small loose experimental, which this year will have around 60,000 copies. But to enlarge them you need the authorization of the Ministry of Ecological Transition. COAG notes that the released fish are insufficient and are asked to 400,000 more, “a figure according to the intensity of the plague”, according to Boza.

From the Ministry explained that the permit depends on a study that is underway José Luis Nieves Aldrey in the Centro Superior de Investigaciones Científicas (CSIC). Its work began in may of Retrobet 2017 and be completed in may 2019. Focuses on to see how it affects the releases of the predator of the trichogramma in the native fauna or their possible hybridizations, which would make the remedy in a worse condition.

The investigator has presented two preliminary work with “optimistic results”, according to forward. It also indicates that the insect requires at least seven years to tackle a scourge which already never will disappear from the area. “We will have to get used to live with it,” says Nieves Aldrey.

While the investigation is ongoing, in the Valley of Genal the patience is running out. Both the producers as well as the mayors of the area are asked time and time again that speed up the paperwork for the permit before it's too late. Even commit to making financial contributions for the purchase of Torymus sinensis, the cost of which is one euro per copy.

“you have to understand that the chestnut is of great importance for the region. And not just for those of us who have farms, and also for the workers who have wages, stores that sell chestnuts or the restaurants and bars that get a good income in the autumn,” concludes Juan Carlos Rubio. The forest is the main tourist attraction of a region in sailing by a tiny insect.

fast advance

A chestnut tree affected by the plague.

The trichogramma was detected for the first time in Malaga in 2014 in several specimens of brown to the outskirts of Ojen, in the region of the Sierra de las Nieves. The following year took the leap to the Valley of the Genal, today infected in its entirety in a greater or lesser extent. Also on the outskirts of Yunquera, where there are about 300 hectares of chestnut groves for which this wasp hermaphrodite campa to their hearts content. It is estimated that you can advance about 25 miles per year, which explains why they have made the leap to The Axarquía, on the other end of the province of Malaga and, hence, to the of Granada.

The trichogramma is the size of a grain of rice, and lays its eggs in the buds of the chestnut tree in spring, which prevents the development of the plant. As a result, production decreases by up to 80%, but also sequesters nutrients from the tree, inhibits their growth and promotes the onset of disease. Only specimens found have been female, which fertilizes their own eggs. This makes it even more difficult to control, which must be biological and not chemical so as not to affect the biodiversity or the human population.