EFFECTS OF CHLORTETRACYCLINE OF HONEY-BEE WORKER LARVAE REARED INVITRO

An in vitro method was developed for rearing worker honey bee (Apis mellifera L.) larvae to the adult stage. Average larval and postdefecation mortalities were 9.5% and 18.1% respectively. Larval and postdefecation development times were similar to worker brood reared in field colonies. Only 1 of 30 sampled adult bees exhibited queen or intercaste characteristics. The in vitro rearing method subsequently was used in studying the effect of the antibiotic chlortetracycline on larval growth and development. A general dose response was observed in mortalities of larvae fed diets containing 0.0025% to 0.05% chlortetracycline. At 0.0025%, larval and postdefecation mortalities were similar to the controls. At this concentration, chlortetracycline effectively reduced larval and postdefecation mortalities of larvae inoculated with 1 × 104 to 1.5 × 108 spores/ml of Bacillus larvae, the causative pathogen of American foulbrood disease. Chlortetracycline doses higher than 0.0025% retarded larval growth and development and caused precocious pigmentation in early larval instars. © 1992.