In this study, it was aimed to investigate the toxic effects of biocidal and nano silver-containing disinfectants, which were used in beekeeping, on bees. Biocidal and nano-silver-containing preparations used in disinfection of hives were obtained from commercial companies. Syrup (1/1 sucrose-water) was given to the control group (Group 1; n = 10). Biocidal preparation (Group 2; n = 10) and nano-silver containing preparation (Group 3; n = 10) were given to one of the experimental groups via an automatic pipette, orally 2 µl per bee. 24 hours after the application, the bees that died in all groups were counted and the midgut tissues of the bees that survived in the groups were taken for histomorphological analysis. No application was performed in the control group (Group 1). Different disinfection solution was used in the group 2 (biocidal ingredient) and Group 3 (nano silver contents). The preparations were applied to the groups by spraying and bee deaths were recorded. Two disinfectants applied to the hives under field conditions, were found to cause more bee deaths than the control group. The highest bee death was in the nano silver group. In laboratory trials, the nano-silver-containing preparation was observed to cause high number of bee deaths and serious damage to the midgut epithelium in histomorphological examinations. The results of the study showed that direct application of disinfectant substances on bees caused serious deaths in the colony. Biocidal and chemical based preparations and hive disinfection should be applied in the empty beehives.