Alien Species in Finnish Nurseries, Phytophthora spp.

Abstract

International trade has increased the risk of pest spread. The climatic change will also improve the establishment of introduced species into new geographical areas. Since the beginning of 1990's Phytophthora cactorum has caused losses in agriculture on strawberries and caused stem lesions on silver birch seedlings in forest nurseries in Finland. P. ramorum was found in Finland for the first time in spring 2004 on marketed Rhododendron spp. plants originating from other EU member states. In August 2004 the pathogen was also found in one Finnish nursery on German Rhododendron catawbiense plants and on several other Finnish Rhododendron spp. cultivars. Most common microbes isolated from the lesions on the Finnish Rhododendron leaves collected in 2005 were Pestalotiopsis sp., P. cactorum, P. inflata and P. ramorum. In pathogenicity trials P. inflata was capable to infect most host plants used in tests including Fragaria x ananassa, Betula pendula, Alnus glutinosa, A. incana, Picea abies and Vaccinium vitis-idea. P. ramorum caused also stem lesions on birch and alder, but was less pathogenic than P. inflata. Pinus sylvestris was resistant to both P. ramorum and P. inflata.