Phytophthora disease on alder (Alnus spp.) in Norway G. M. Strømeng1, M. B. Brurberg1, M. L. Herrero1, W. Couanon1, A. Stensvand1, I. Børja2 and V. Talgø1 1 2 Norwegian Institute for Agricultural and Environmental Research, Ås, Norway; Norwegian Forest and Landscape Institute, Ås, Norway. [email protected] In 2012, conspicuous dark, bleeding cankers were observed on trunks of dying trees in natural stands of grey alder (Alnus incana) along the shore of lake Årungen in Akershus county in Norway. Phytophthora alni, which has been killing alder in Europe during the past two decades, was suspected to cause the disease. Work was initiated to identify the causal agent and assess the damage. A survey in the alder population around the lake, revealed that out of approximately 6000 examined trees, nearly 200 showed typical symptoms on the trunk. At the sites where the damage was most severe, 20 % of the trees showed symptoms. Samples for isolation of potential pathogens were collected from the leading edge of canker wounds. The samples were rinsed in tap water and small pieces were plated on selective medium for Phytophthora (PARPH). After a few days at room temperature, colonies emerged from the tissue samples. Subcultures on V8 agar were identified to P. alni ssp. uniformis by PCR using three primer pairs to identify the subspecies. This is the first time P. alni has been found in Norway. The same subspecies was also isolated from symptomatic grey and black alder (A. glutinosa) by a pond located approximately 1 km from the lake. Symptoms observed on alder at other locations indicate that the disease may be widespread in south-eastern Norway. By spring 2014, we do not know if there are other subspecies of P. alni present in Norway, but a survey of Phytophthora on alder will take place in a larger region later this year to investigate distribution and the possible presence of other P. alni subspecies. 50 View publication stats
