of the honeybee and test their insecticidal effects on adult honeybees. 2. Materials and methods 2.1. Insect samples Samples of honeybees were collected from bee farms in the vicinity of Ordu,Turkey from May to September.The adult bees collected from the hives were placed in plastic boxes (20 × 20 cm) with punched lids for ventilation, and sugar cake was given in small pieces until the bees were transported to the laboratory for examination. Following this, healthy, diseased, and dead adult bees were separated for observation and used to isolate bacteria that could cause disease. 2.2. Isolation of bacteria Isolation and purification of bacteria was carried out individually from dead and live honeybees. The live and dead adults were individually surface sterilized by using 70% ethanol for 3 min [8] and washed 3 times with sterile water. The dead honeybee carcasses were homogenized in feeder medium using a glass tissue mill, and 2 layers Abstract: The honeybee (Apis mellifera) is an important pollinator insect. Any pathogenic infection in this beneficial insect is undesirable. In this study, bacterial diversity in beehives was investigated to determine the potential of pathogenic bacteria in honeybees. To do this, bacterial isolations were carried out from dead and diseased adult bees collected from 9 districts in Ordu Province in Turkey.Twenty species of pathogenic bacteria, 18 of which were nonsporeforming Staphylococcus lentus, Klebsiella oxytoca, Citrobacter freundii, Leucanostoc mesenteroides ssp. cremoris, Kocuria rosea, Kocuria kristinae, Sphingomonas paucimobilis slashline, Burkholderia cepacia, Leucanostoc mesenteroides ssp. dextranicum,Hafnia alvei, Escherichia coli, Aeromonas salmonicida, Citrobacter braakii, Pantoea agglomerans, Streptococcus equi ssp. zooepidemicus, Staphylococcus pseudintermedius, Staphylococcus lugdunesis and Staphylococcus vitulinus and 2 sporeforming Bacillus licheniformis and Paenibacillus polymyxa, were isolated and identified from the honeybees. The infectivity of these bacteria were also documented with bioassay experiments on the healthy bees.The highest insecticidal effectwas determinedwith Bacillus licheniformis (84%), Escherichia coli (84%), and Streptococcus equi ssp. zooepidemicus (80%) on the adult honeybees.This result confirms that the honeybee contains a very large number of bacterial species and that the majority of them are pathogenic for the species in Turkey. In addition, some of the entomopathogenic bacteria used for biological control can have negative impact on this economically important insect.