First Report of Fire Blight Caused by Erwinia amylovora on Cotoneaster dammeri cv. Skogholm in Croatia

In July of 2007, fire blight symptoms were observed on Cotoneaster dammeri cv. Skogholm in a nursery near Županja, Vukovarsko-Srijemska County, in eastern Croatia. In this region, the first outbreak of fire blight was noted on apple in 1995 (2). Symptoms on cotoneaster were necrotic shoots and petioles. Immunofluorescence assay (IFA) with polyclonal antibodies (Loewe Biochemica GmbH, Sauerlach, Germany) was performed on extracts from blighted C. dammeri cv. Skogholm shoots and were found to be positive for Erwinia amylovora. Round, mucoid, whitish colonies were isolated from extracts of plant tissues with symptoms of fire blight spread on King's medium B and incubated for 2 days at 28°C. Bacterial ooze and necrosis of the inoculation site were observed on immature pear fruits inoculated with a 10⁶ CFU/ml suspension of the isolate. Bacteria were reisolated and the species identity was confirmed by PCR and primers targeting pEA29 DNA (1). E. amylovora was previously reported only on native Cotoneaster spp. (3). To our knowledge, this is the first report of fire blight on C. dammeri cv. Skogholm from a commercial ornamental nursery in Croatia.