Invasive Species Compendium

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Abstract

First report of Erwinia amylovora, the causal agent of fire blight, on pear in Finland.

Abstract

In autumn 2014, severe disease symptoms resembling those of fire blight were observed in pear trees (Pyrus communis cv. Concorde) planted in 2009 in an orchard in the Aland archipelago in southwestern Finland. The symptoms included dark cankers with cracked margins on the trunk, brown discoloration under the bark, and blackening of shoots and leaves. Blighted fruit appeared shriveled and remained attached to the tree. No oozing of bacteria from any part of the plant was detected. The initial symptomatic sample was collected in September 2014 and subjected to isolation, identification, and pathogenicity testing of the pathogen following the EPPO protocol for diagnosis of E. amylovora. Based on the results of immunofluorescence (IF), molecular (PCR assay) and pathogenicity tests, the causal agent was confirmed as E. amylovora. The sample was also confirmed as E. amylovora-positive at the Food and Environment Research Agency (UK), by plating, TaqMan PCR and fatty acid profiling. After the initial sample, 37 additional samples were collected in October 2014 from the same orchard, out of which 14 were found positive by IF and PCR. Fire blight has been surveyed for decades in Finland, but this is the first confirmation of its occurrence.