Uploaded to his off-road vehicle, Juan Carlos Rubio travels a dirt road that crosses an enchanted forest. It is the appearance of the old 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. It houses about 150 trees, but the farmer goes directly to a dozen of them with barely leaves. The few that keep are shrunk on themselves. "It is the clear example of chestnut trees affected by the wasp," he explains. Drycosmus kuriphilus, arrived from China to Malaga in 2014 and, since then, has been in check to the farmers. "As we continue like this, it's going to be a catastrophe," says Rubio.
The insect measures only 2.5 millimeters, but endangers the nearly 4,000 hectares of chestnut from the Genal Valley. The area is home to some fifteen small towns and for some these trees are their main economy. The Coordinator of Organizations of Farmers and Cattle Ranchers (COAG) calculates that there are 1,500 families linked to the production of chestnuts. The sector generates ten million euros per year and produces an average of four million kilos per year. 60% is exported to Italy, the United Kingdom, the Netherlands and Belgium.
A volume that this tiny insect can make disappear. "The chestnut tree is vital for these people, what would happen without it?" Wonders Miguel Angel Herrera, mayor of Genalguacil, a town of 405 inhabitants that two decades ago had 575. The population drop affects the entire valley, which 2000 to 2017 went from 8,138 to 6,935 inhabitants, according to the INE.
The fear of the Asian hornet is present even in years like this, when the production of chestnuts has reached a record of five million kilos. Since the insect went into in the rondeña mountains, its ravages are increasing exponentially. "We need to control the plague now," says Francisco Boza, head of COAG Andalucía. "Some people have between 30 and 50% less chestnuts than a few years ago," says Mateo Rosado, president of the ValGenal Cooperative, located in Pujerra.
400,000 insects to end the plague
So far, the best way to fight the plague is with another insect, called Torymus sinensis and that also comes from China. It is your natural predator. The Junta de Andalucía has been making small experimental releases, which this year have reached around 60,000 copies. But to expand them you need the authorization of the Ministry of Ecological Transition. COAG highlights that the released specimens are insufficient and ask for 400,000 more, "a figure according to the intensity of the plague," according to Boza.
The Ministry explains that the permit depends on a study being carried out by José Luis Nieves Aldrey in the Higher Center for Scientific Research (CSIC) Its work began in May 2017 and will be completed in May 2019. It focuses on how it affects the release of the predator of the wasp in the native fauna or its possible hybridizations, which would turn the remedy into a worse disease.
The researcher has already delivered two preliminary works with "optimistic results", as he advances. It also indicates that the insect requires at least seven years to tackle a plague that will never disappear from the area. "We'll have to get used to living with him," says Nieves Aldrey.
While the investigation continues its course, in the Genal Valley the patience is running out. Both the producers and the mayors of the area are asking again and again to accelerate the process of the permit before it is too late. They even undertake to make economic contributions for the purchase of Torymus sinensis, whose cost is one euro per copy.
"You have to understand that chestnut is of great importance for the region. And not only for those of us who have farms, but also for the workers who throw wages, the shops that sell chestnuts or the restaurants and bars that earn good income in the fall, "concludes Juan Carlos Rubio. The forest is the main tourist attraction of a region in sail for a tiny insect.
The wasp was detected for the first time in Malaga in 2014 in several chestnut trees outside of Ojén, in the Sierra de las Nieves region. The following year he made the leap to the Valley of the Genal, today infected in its entirety to a greater or lesser extent. Also to the environs of Yunquera, where there are some 300 hectares of chestnut trees for which this hermaphrodite wasp is at ease. It is estimated that it can progress about 25 kilometers a year, which explains why it has made the leap to La Axarquía, at the other end of the province of Malaga and, from there, to that of Granada.
The wasp is the size of a grain of rice and lays its eggs in the chestnut buds in spring, which prevents the development of the plant. As a result, it reduces production by up to 80%, but also sequesters the tree's nutrients, slows its growth and favors the appearance of diseases. Only female specimens have been found, which fertilize their own eggs. This makes control even more difficult, which must be biological and not chemical so as not to affect biodiversity or the human population.