One of the iconic images of France is of a man or a boy on a bicycle wearing a beret, carrying a baguette and cycling down a scenic road lined with plane trees. We still have bicycles, baguettes and a few berets but sadly, a disease called canker stain is killing off many of our iconic plane trees.
Now the disease has come to our town near Aix-en-Provence, Le Tholonet, as it spreads from Italy throughout southern France and into Spain. I attended an informational meeting for citizens about the problem last week. Workmen are already taking down the 16 affected trees on one of the town’s main roads. Thankfully, the disease has not spread to the scenic road (photo above) leading up to our local chateau.
I often wonder what our high taxes pay for in France. Well, I learned that an impressive environmental and agricultural protection service is certainly one thing.
Plane tree canker stain is a downright difficult problem. Understanding requires a little history. The British imported the original trees into France in the 17th century. All of the plane trees are thus descendents of the British hybrid of American and Greek specimens. So ALL of the trees are susceptible to the canker disease, which is believed to have arrived in Marseille from the United States during World War II.
The canker becomes visible as a violet stain on the bark and branches begin to die. The difficulty arises from the way the disease travels via the root sytems to trees nearby. Spores can also be spread via dirt, dead branches, leaves and the equipment used to uproot the sick trees. In addition, the spores remain active for 10 years and in damp soil conditions, possibly even longer. So in the case of our town, even though only six trees have canker damage, 16 trees must be removed at a cost of 25,000 euros. All of the equipment and the workmen’s clothing must also be disinfected and the wood and branches must be burned at a special toxic waste site.
To eradicate all the infected root systems requires clearing a 35-meter diameter circle around each bad tree. Since the trees are planted more closely together than that, many healty trees must go too. Water easily transports the spores so the plane trees lining France’s canals are seriously threatened. In south western France most of the plane trees lining the famous Canal du Midi are already gone. The diseases is also spreading in Greece, Italy, Switzerland, Armenia and Iran. I do not know the situation in the United States, but as I never saw any plane trees there I fear they may already be gone along with elm trees.
The agricultural/environmental experts who spoke at the town meeting I attended explained that French scientists have already created a new plane tree hybrid that is naturally resistant to the canker. However, the new trees can only be planted in virgin territory as some that were used to replace diseased trees have caught the illness. Tests are being conducted to see if that was due to a particularly humid and difficult site or not. In the meantime, the scientists are working to create more resistant plane trees but nothing is nearly ready to go. So in our town the plane trees will be replaced with linden trees.
Among the many questions from the small audience at the meeting was ,”What about trees on private property?” The answer is that homeowners are responsible for removing their diseased trees. But if they do it poorly with uncertified garden services who fail to disinfect equipment or properly dispose of the sick trees, private removals can spread infection. In cases where trees on private property threaten to fall on roads or sidewalks, the government can step in. However, the procedures for doing so are long and complicated. The experts said they have been going through the process for over a year to try to get one homeowner in the region to remove sick trees. Eventually they expect they will have to go in with police to do so over the owner’s objections.