Root collar rot on Alder
The planting of contaminated alders from nurseries is responsible for the spread of Phytophthora disease of alder (root collar rot). This is confirmed by new cases, in which forest owners are confronted with the sudden dieback of Alder plantations. |
The infection with the pathogen Phytophthora alni takes place in the root zone of alders via water, within which the free-moving flagellated spores (zoospores) of the pathogen are present. These zoospores can reach nurseries through contaminated water during flooding. Another possibility is the watering of the plants with zoospore infected river water. Furthermore, plant material is often purchased which is already infected in the root zone.
Infection happens in seedbeds or nurseries. Root infections through Phytophthora alni are only possible in artificial soils of seed beds and nurseries. In forest soils the spores are intercepted by competing fungi, which reduces the risk of infection. The alders do not show above-ground symptoms of infection until several years after planting. In the root zone, the phytophthora infection is not macroscopically visible. For this reason, it is not possible to check plants before purchase in order to find infected alders and reject them.
A further possibility is the production of container plants in controlled phytophthora free substrate, whereby uncontaminated irrigation should also be ensured. A safer way is also the purchase of controlled, zoospore-free alder plant material, which is offered by some nurseries as well as nurseries of the Austrian Research Centre for Forests (BFW). Further information: Dr. Heino Konrad, Department of Forest Genetics, Tel.+43 (1) 878 38-2112, E-Mail: firstname.lastname@example.org.
Forest owners should clear alders which are infected from the roots up, and reforest with other tree species. As the Phytophthora disease of alder is host-specific to the genus Alnus, there is no risk to other tree species.
Federal Research and Training Centre for Forests, Natural Hazards and Landscape (BFW)
Austria, 1131 Vienna, Seckendorff-Gudent-Weg 8 | Tel.: +43 1 878 38-0
Autor: Cech T.