Relationships between Apis mellifera and Erwinia amylovora: Bioindication, bacterium dispersal and quarantine procedures

It has been recently demonstrated that honeybees can be used to monitor the presence of Erwinia amylovora in the environment. The monitoring protocol involves setting up stations (consisting of three hives each) in infected areas, at the edges of infected areas, or in apparently non-infected areas. From 2000 to 2002, over 500 samples of pollen and honeybees were analysed for the fire blight pathogen by a new chemiluminescent PCR-ELISA rapid method. This monitoring programme demonstrated that honeybees can be an efficient and economic tool to detect the bacterium, even in the absence of symptoms. In fact, in several cases, E. amylovora was detected in samples from areas where no symptoms of fire blight had been observed. On the basis of results presented at the 9(th) International Workshop on Fire Blight, a study was carried out in 2002 to evaluate, under greenhouse conditions, the role of honeybees in the dissemination of E. amylovora from experimentally inoculated pear flowers and contaminated hives to healthy pear flowers and honeybee matrixes. Our results show that, after contamination, honeybees can act as carriers of live bacterial cells of E. amylovora for only 48 hours. After this period, no viable E. amylovora cells were found in non-inoculated pear flowers visited by insects, on honeybee bodies or intestines, or in any of the analysed beehive products (honey, pollen and wax). These and previous results provide useful data to establish prophylactic operating procedures to allow beehive movement in disease-free areas. The quarantine procedures mandate closing the hives and keeping them in a temperature controlled chamber (between 15 and 20 degrees C) for 48 hours, or for 24 hours only if they have been treated with oxalic acid, which inhibits E. amylovora.