Graphiose of the Elm

The graphiose , also named “disease of the elm of Holland”, is a fungic disease of the Asian Orme probably of origin, which appeared in 1919 for the first time at the Netherlands (from where its name) and in the north of France, then developed in all Europe. Its introduction in North America (the United States then Canada) in 1928 causes very serious damage on the American Orme which it destroys on considerable surfaces. Towards 1970, a new stock even more aggressive was introduced in Europe with the favor of imports of Grume S.

It acts via the Champignon Ophiostoma ulmi ( sensu lato ) transmitted by insects of Scolytinae. One of the primary symptoms is a deformation of the bark branches of the adult elm. One recognizes also a sick tree with his desiccated foliage which remains despite everything in place. Black scratches appear sometimes under the bark, from where the name graphiose. The mushroom is famous to be transmitted of two manières : by the insect vector and contacts racinaires (a contamination by tools of size is also possible). The scolyte vector reproduces on the dying trees. The adult needs to consume a little bark elm to reach his sexual maturity. It is during this meal of maturation that it transmits the disease to the operational trees while transporting spores of a sick tree to an operational tree. The close trees are in close contact via “ Clerc's Offices ” of roots. The mushroom is able to pass from a sick tree to a healthy neighbor via these Clerc's Offices. That makes it possible the disease to very effectively disperse in a relatively monospecific hedge where the elms are in contact racinaire. There is no remedy for this disease; it is generally recommended to cut down the sick tree so that it contaminates of them less others (Prophylaxie), although in general the evil is already made. The graphiose affects all the species of elms American and European. The elms of forest less prone to the disease thanks to their more isolated situation and are possibly mixed. The old branches and the trunk die, but the stock remains often alive when the tree is cut in a hedge. That explains the persitance elm which remains very present in some Bocage S and Haie S. Malheureusement, the elms do not reach any more of the important sizes because as soon as they present branches 4-5 cm in diameter, they can be contaminated by the scolytes vectors and die.

See too

External bonds

Arte

Random links: