The Phytophthora disease of alder occurs in Belgium
Dr Cavelier from the Centre de Recherches Agronomiques de Gembloux recently informed the EPPO Secretariat that the Phytophthora disease of alder (formerly on the EPPO Alert List) has been found for the first time in Belgium. The pathogen was identified in September 1999, in Alnus glutinosa stands (7 years-old) near river Dyle, in the commune of Grez-Doiceau, in Wallonie. In 1999, the phytosanitary status of A. glutinosa rapidly deteriorated in Wallonie, as severe die-back of alders was seen along several rivers (Amblère, Honnelle, Lesses, Mehaigne, Ourthe, Sûre, Vierre). It is stressed that the development of this new disease will have disastrous consequences on the ecology of riverbanks, as A. glutinosa is a major component of these ecosystems: high resistance to flooding, deep root system maintaining riverbanks and providing shelter for fish reproduction, light canopy favourable to good regulation of physical characteristics of water. In addition, A. glutinosa provides high quality wood and constitutes an important element in the landscape. Several recommendations are made to prevent further spread of the pathogen. In affected areas: 1) systematic destruction of trees is usually not recommended as this may favour further spread, prevent the identification of resistant trees and destabilize river banks; 2) if trees are destroyed, stumps should not be left near water streams or humid zones; 3) cutting back of Alnus trees should be done over short distances (it has been observed in UK that this usually provided healthy trees without destabilizing riverbanks), 4) when replanting, other tree species should be used whenever possible. In order to prevent the entry of the pathogen into areas where it is still absent: 1) Alnus wood should not be used for riverbank installations, 2) movement of water, mud, fish should be avoided, 3) disease-free planting material should be used, 4) tools should be
disinfected. Surveys will continue in Belgium to determine the extent of the disease, as well as studies on the genetic variability, pathogenicity and epidemiology.
Cavelier, M.; Claessens, H.; Etienne, M. (1999) Premier signalement du Phytophthora de l’aulne (Alnus glutinosa) en Belgique.
Parasitica, 55(2-3), 63-71.
Claessens, H.; Cavelier, M. (2001) Le point sur le dépérissement de l’aulne.
Forêt Wallonne. Cahier Technique n° 13, 11-15.
Fiches d’information sur la maladie de l’aulne.
Edited by ‘Centre de Recherches Agronomiques de Gembloux’ and ‘Faculté Universitaire des Sciences Agronomiques de Gembloux’.