Occurrence of Erwinia amylovora on insects in a fire blight orchard

In order to screen for natural dissemination of fire blight under field conditions, insects were caught in an experimental orchard and assayed on semi-selective agar plates and by BIO-polymerase chain reaction for their contamination with Erwinia amylovora, the causative agent of the bacterial disease. The pathogen was detected on 15 out of 348 insects collected (4.3%). The insects contaminated with E. amylovora have different living habits and belong to four different orders (Homoptera, Coleoptera, Hymenoptera and Diptera) and at least eight insect families (Aphididae, Psyllidae, Coccinellidae, Curculionidae, Ichneumonidae, Formicidae, Apidae, and Muscidae) and to other Brachycera. After contact of insects with E. amylovora, the pathogen could survive at least 5 days in/on the green lacewing (Chrysoperla carnea) and 12 days on aphids (Aphis pomi).