Honey Bee, Apis mellifera Toxicity of Five Antibiotic Formulations Used against the Fire Blight Control in Apple Orchard

The use of antibiotics in agriculture to combat bacterial plant diseases has become a critical area of study due to its implications for environmental safety and agricultural sustainability. One major concern is the potential impact of these antibiotics on pollinators, particularly honey bees. In this study, the acute toxicity of five antibiotics on adult honey bees was evaluated using oral and contact spray bioassays, with six serial dilutions based on the recommended concentrations. The results showed that copper hydroxide was toxic to honey bees when administered orally, with an LD₅₀ of 9.5 μg/bee. In contrast, the other four antibiotics-oxolinic acid, streptomycin, Bacillus subtilis, and oxytetracycline dehydrate-exhibited no toxicity in either the oral or spray bioassays. The high oral toxicity of copper hydroxide indicates that its application should be carefully managed during apple blooming to minimize harm to pollinators. These findings highlight the variability in antibiotic toxicity and underscore the need for careful consideration in their agricultural use to protect pollinator health.