A Stain on the Planes of the Canal du Midi




A virulent incurable canker stain disease is killing magnificent plane trees shading the banks of the 240km-long Canal du Midi and threatening the survival of this extraordinary 17th century feat of French engineering.

Picture: credit FrenchNewsOnline under Wikicommons

Deadly disease threatens thousands of Canal du Midi plane trees. Photo: FrenchNewsOnline

According to a report in Le Petit Jornal January 23, the canal authority VNF-Voies Navigables de France (Inland Waterways of France), is engaged in a war to eradicate a disease which, since 2006, has seen 480 of the 60,000 plane trees that line the waterway – some 250,000 trees shade the canal between Bordeaux and Sète — uprooted and burnt on site, in scenes reminiscent of a great plague. Latest reports says some 2000 plane trees are being targeted for destruction in a bid to halt the march of the fungus along the waterway linking Toulouse to the Mediterranean.

Along this Unesco World Heritage site teams of sanitary inspectors, scientists and biologists join expert woodsmen, covered head-to-foot in white overalls and gloves like forensic teams at a crime scene, to uproot the trees. Because of the highly contagious nature of the spores that cause the infection, (a simple touch can lead to contamination) all traces of diseased tree must be eradicated on site and all equipment and plant used must be carefully disinfected before being moved on.

Because the disease can spread through the root system, any other plane tree in a radius of 50 metres, even if apparently healthy, also has to be destroyed. The costly work further involves consolidating the banks of the canal — the plane trees were planted during the original construction, to reinforce the banks — and replanting with other shade varieties or more resistant strains of plane to retain the canal’s unique features.

The trees serve a threefold purpose: to buttress the banks, shade canal boats, which originally transported textiles and wine but today carry canal boating enthusiasts, and reduce water evaporation by the strong Midi sun.

Speaking of the outbreak of “Ceratocystis platani” now threatening the canal’s trees along with those in town and village squares across the Midi-Pyrenees, Dominique Tilak of the National Forestry Department told La Dépêche du Midi: “The first appearance in Midi-Pyrenees dates from June 17, 2005. But it must have been present before. The concern is that the canker stain is always fatal. There is no effective treatment. The only hope comes from developing a new kind of plane tree that will resist canker stain.”

The war now being waged began … during another war, arriving, it is believed, with US troops. “In 1944 American forces landed in Marseilles with ammunition boxes that were made from infected sycamore wood,” said Sandrine Kikolski, who monitors the disease for the Plant Protection division of the Regional Agriculture and Forestry Department. “The fungus took its time”, she said, “but gradually it took root in Provence and Languedoc, Corsica, Rhone-Alpes, Savoy, and is now becoming embedded in the region.”

Jacques Noisette, Communications Officer at VNF said: “We do this tree culling in the winter, when the spores are less volatile. The fact that the canal is also closed to traffic is a good thing, because the fungus can be conveyed by water. VNF is also expanding its monitoring with a general inspection of plane trees between Sète and Bordeaux – the length of the 360-km network. “From the days of Riquet, the canal has been lined with different varieties, ash, willow and poplar,” Jacques Noisette added, indicating replantings would not be restricted to plane trees.

 

When the outbreak of the disease was first identified in 2006 there were fears that the Canal du Midi risked seeing all its plane trees destroyed within 25 years, a nightmare scenario still not fully excluded.

After detecting the first cases of plane trees infected with canker stain in 2006 at Villedubert, east of Carcassonne, VNF discovered four new foci located between Puichéric and Argens-Minervois, evidence that the first attack of killer fungus (Ceratocystis platani) was not an isolated incident.

Should we fear that the plane tree will disappear entirely in the South of France? “I do not think so. We have acted aggressively and hopefully in time to limit the impact of the disease, “Sandrine Kikolski told La Dépêche du Midi. “But we must not lower our guard. In the Provence-Alpes-Côte d’Azur region, 2000-3000 plane trees die each year from the fungus,” she said.

Householders with plane trees on their property are urged to seek advice from local councils and Mairies about disposing of leaves and trimmings from pruned trees on site, as part of efforts to contain further outbreaks of the disease.

The Canal du Midi is one of Europe’s longest and widest canal systems which with its two extensions — Canal de Garonne and the Rhône-Sete canal — links Bordeaux on the Atlantic to Sète on the Mediterranean before continuing up the coast to the Rhone Basin in the Camargue. In 1994 it was designated a World Heritage Site.

The network straddles the departements of Herault, the Aude and Haute Garonne and the Midi section runs over 241 km between Toulouse and Marseillan where it opens into the Etang de Thau near Sète.

The driving force behind the Canal was one of Louis XIV’s Salt Tax Collectors. Pierre-Paul Riquet, born in Beziers in 1604, built the first sections of the canal using his own wealth after obtaining permission from Colbert the engineering genius who was Maréchal de France under the Sun King. Work began in 1666 and was completed in 1680.

The King's local Salt Tax collector. Pierre-Paul Riquet, was the driving force behind the Canal

As anyone who has travelled around the area knows, the majestic twin lines of plane trees that appear and disappear on the horizon are a signal to watch out for an upcoming glimpse of the canal or, even better, a bridge crossing.

Much more history on this engineering wonder can be found here in a fact-packed article by Geoff Taylor written for the Crème de Languedoc website. He tells how the canal became technically feasible only because of the Black Mountain and its abundant springs. The article provides several interesting links about the canal.

A full description is also found here on the Unesco heritage site

A local school principal, Philippe Calas, Headmaster at Portiragnes School (3400) near Béziers maintains a detailed site in French and English which covers much more than just the history of the canal. He branches out from the canal to discuss history, culture and sport in side essays on the Cathars, Rugby, Wine and Food.

Story: Ken Pottinger
editorial@french-news-online.com

UPDATE: Reader Nicola Blakemore has her own account of the eco-disaster plus a dramatic night fall picture, showing the yawning gap in the lineup, here



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