when “Sud Ouest” followed the Chinese trail of the first hornet to arrive in France via Lot-et-Garonne

Find a beekeeper there and the hornet will come to you. It’s 42 degrees on the hills of Zhou Wu Ka, the shirt sticks to the back. A storm of rain fell in vain.

Only the van’s air conditioning provides a little fresh air in the humidity of the Chinese summer. Li Hua-fang offers tea and is amused by his strange visitors. Around thirty beehives shaped like djembes are lined up under the window. Landing net at arm’s length, four entomologists from the National Museum of Natural History in Paris move slowly through the aisles, listening in their ears for the buzz of a possible hornet: “I have one! »

A three-hour drive from sprawling Shanghai, the team of Claire Villemant, a researcher in the Museum’s entomology unit, is going to collect hornets in the area around Yixing. Scientists are following the trail of “Chinese pottery” imported into Lot-et-Garonne and which are said to have made the bed of the Vespa velutina species in France. Introduced more than five years ago, the Asian hornet, terror of our bees, is reported to date in 32 departments [le 25 septembre 2010, NDLR].

“The city of pottery”

Terracotta teapots made Yixing famous during the time of imperial China, and today they have earned it the international title of “city of pottery”. Its ceramists have a showcase in the brand new district reserved for them in Dingshu, on the outskirts, and pottery factories with open-air warehouses parade along the highway.

“It could correspond…” reasons Claire Villemant. An entomologist’s daydream: the DNA of hornets hunted in China will be sequenced and cross-referenced with the strain imported into Lot-et-Garonne. First to remind that this is only an “introductory hypothesis”, the scientist will be determined in the fall. Finally, we will verify “the pottery theory” – as the Agenese entomologist Jean Haxaire calls it -, too quickly presented for granted.

“It clicked”

Specializing in the cultivation of bonsai, he sourced his pots from Chinese artisans.

“There are a lot more exchanges than we think. Don’t just keep this track,” insists a former Lot-et-Garonne nurseryman. He is none other than the importer of the famous pottery. “Don’t use my name…” he simply demands. He had never spoken out, often he thought he came across as the naughty merchant, he who, from the outset, played fair. Specializing in the cultivation of bonsai, he sourced his pots from Chinese artisans. Almost everywhere in the country and “80%” in Yixing.

In the summer of 2004, he surprised the beast hovering in the courtyard of his house, in the village of Pinel-Hauterive, on the banks of the Lot. A large black wasp, with an unstoppable orange-yellow stripe. It was only two years later that the presence of the Asian hornet was established in Lot-et-Garonne. What if he was the first to see it? In the following autumn, yet another prospecting trip to China took him to the province of Yunnan. It was by chance at a local market that the nurseryman came across a hornet that was a carbon copy of the other.

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The explanation will come to him on his return. “In November, when the oak leaves fell, I saw the nests… It clicked. » Hanging from the branches, not one, but two nests as big as washing machine drums, something never seen before for anyone looking up in Lot-et-Garonne. “I felt absolutely in my duty to report this, in complete transparency. » In the following month, he alerted the plant protection service, his privileged contact at the Lot-et-Garonne prefecture, and went so far as to make a phone call to the Museum, where he was invited to establish a form. Which he hardly has time for. The nests seem abandoned to him, there is not the slightest coming and going. As a precaution, the owner removes them from the trees, one with a gun, the other by sawing off a branch.

A handful of queens

A year passes… Jean-Pierre Bouguet from Nérac will be credited with capturing the first hornet of the Vespa velutina species in France in his garden. “We recommend to all entomologists the most extreme vigilance regarding this species and its possible expansion,” Jean Haxaire, Jean-Philippe Tamisier and Jean-Pierre Bouguet, authors of the first article then published in the “Bulletin de the Entomological Society of France”. Each year, the Museum evaluates the ground gained by the insect at a distance of 100 kilometers. “The thickness of a department”, converts Claire Villemant.

Incredible as it may seem, the introduction of a few founding females, and perhaps only one, would have been enough for it to establish roots in France. “The genetic characteristics of different individuals in the French population are similar. » So the queen(s) fertilized in a nest in China would have found refuge, long enough to overwinter, in the corner of a presumed box of bonsai pots ready to be taken on a long journey by container ship.

A hit that left Shanghai, landed not in Bordeaux but in Le Havre, and opened in the spring in Pinel-Hauterive. “But it’s not necessarily this way that it came in,” the former nurseryman wants to believe. After all, isn’t the logistics base of Gifi stores, a major importer of manufactured products in China, located in Villeneuve-sur-Lot? “We have always tried not to stigmatize anyone,” says Hélène Delefosse, head of the environmental protection service at the prefecture.

DNA of the Yixing hornet will reveal the key to the enigma

There are around a hundred of them bathed in alcohol, confined in a fridge in the Museum’s entomology laboratory. Vespa velutina hornets collected this summer at capture locations duly referenced by GPS. The catches will shortly be entrusted to the CNRS laboratory in Gif-sur-Yvette, in the Paris region. The DNA collected from the specimens’ legs will be analyzed by Mariangela Arca, a thesis student. The results should come “before the end of the year”, hopes Claire Villemant.

Although she and her team found only a handful of hornets at the beekeeper in the village of Zhou Wu Ka, the entomologists did their best to comb the terrain in the hinterland of Shanghai. Going hunting in a forest park on the outskirts of Yixing, they got their hands on a nest formed in a hedge. The point of the maneuver: to get as close as possible to the alleged genetic strain imported into France.

Expanding

At a time when beekeepers are desperate to see the Asian hornet attack their bees, why bother with its DNA? “There are a lot of unanswered questions before putting the puzzle together,” explains Claire Villemant. “This allows us to study the fate of the invasive line… Does its genetic heritage differ greatly or not from the original population? Has the bottleneck represented by a handful of founding females influenced the ecological potential of the species? »

As far as we know, the news from the front is not very encouraging. The Vespa velutina species, which extends from northern India to eastern China, seems capable of colonizing the entire French territory and beyond. “The combination of climatic variables in the countries of origin is close to that of Europe. Climatic conditions, particularly towards the north, are relatively favorable. One of the main limiting factors is drought. »

Hypotheses to rule out

What if the DNA taken does not correspond to the French lineage? Already, the sequencing of hornets from Yunnan, once elevated to the rank of lead by entomologists, had the merit of ruling out this province in southern China. Other specimens, collected in Indonesia and Laos, will be part of the lot analyzed. They will undoubtedly help to close other doors.

The only certainty is that the “home of dissemination” of the species is indeed in Lot-et-Garonne. But wouldn’t he have been spotted in the department for the simple reason that there are keen observers of nature there? “There is a very efficient network of entomologists in France,” says Jean Haxaire, professor of biology at the Baudre high school in Agen and entomologist attached to the Museum. “An insect the size of Vespa velutina would not have escaped them for long, as until then there was only one species of hornet in France. The idea circulating that the Asian hornet has been in France since 1996, and even before, is also totally fanciful. » And, adds Jean Haxaire, “just as hypothetical is the existence of a second source of dispersion in Bordeaux”, sometimes cited in an article.

In 2004, the first nest filmed

At least the news will relieve beekeepers of vain anger. Although the Hauterive nurseryman reported the presence of clandestine nests in the fall of 2004, it was undoubtedly too late. There was already another at the top of an acacia tree in Bourgougnague, near Lauzun, in the north of the Lot-et-Garonne department. 24 kilometers as the crow flies. “It was amazing, a perfectly round nest, as big as three basketballs, 25-30 meters high. I thought of a bird’s nest,” says Francis Marboutin, a neighbor.

Naturalist at the Mazière reserve, Laurent Joubert came, camera in hand. “There were still animals coming in and out. » Although he kept the sequence on a video cassette labeled “October-November 2004”, no contact had then been made with an entomologist.

Fatality?

And what about the information immediately delivered to the Plant Protection Service: “We were hard-pressed to take any real action. The SPV made its report and afterwards, there is a hole,” agrees a state agent today. “At the Ministry of Agriculture, we deal with beekeeping, but not with wildlife. At the Ministry of Ecology, we deal with wildlife, but not beekeeping. There was indeed an embryonic approach but it came to nothing. »And to deplore a “missing link” in the case of invasive species.

The introduction of the hornet, collateral damage of the boom in trade with Asia? “Historically, maritime transport is a vector for the introduction of foreign fauna and flora,” recalls Vincent Groizeleau, editor-in-chief of the information site meretmarine.com. “Containers are normally treated with the use of insecticides but, given the scale and diversity of traffic, we cannot guarantee perfect effectiveness, as the introduction of the Asian hornet seems to demonstrate. »

Landmarks

Fall 2004. Characteristic nests of the Asian hornet are observed, two in Hauterive, one in Bourgougnague. November 1, 2005. The first hornet of the species Vespa velutina is captured in a garden in Nérac. The Museum is informed of the presence of a nest in Tombeboeuf. May 8, 2006. Other specimens are trapped in the Mazière reserve, near Tonneins. May 20, 2006. Official report of the insect in France. 2009. Its presence is attested in 32 departments