Mixture toxicity of tebuconazole and fluopyram to honeybee (Apis mellifera L.): Effects on survival, feeding and antioxidant defenses
2025
Neama S. Saeed | Sayed A. Ahmed | Zeinab H. Ahmed | Abdulraouf M. Amro | Ibrahim A. Mohamed
Tebuconazole + fluopyram is a new binary mixture fungicide product that is widely used to control many plant fungal pathogens and nematodes in several agricultural crops worldwide, including Egypt. However, there is a lack of information about their toxicological effects on honeybees (Apis mellifera L.). In the current study, the lethal and sub-lethal toxic effects of mixture tebuconazole + fluopyram were examined on A. mellifera workers. Tebuconazole + fluopyram exhibited low acute toxicity to A. mellifera foragers (the 96-h LC50 value was 1.389 mg a.i. ml–1). Sub-lethal effects of tebuconazole + fluopyram on survival, body weight, food consumption and antioxidant defenses of A. mellifera were determined by chronic oral exposure of A. mellifera workers to sugar syrup which contained two sublethal concentrations of the fungicide, 0.139 mg ml–1 (1/10 of 96-h LC50) and 0.278 mg ml–1 (1/5 of 96-h LC50), along with clear sugar syrup as a control for 18 days. Honeybees exposed to both sublethal concentrations of tebuconazole + fluopyram showed a significant decrease in the bees’ survivability and dry body weight. Sugar syrup and pollen consumption by the exposed A. mellifera were relatively less than by the controls. Tebuconazole + fluopyram also induced disruptions in the enzymatic antioxidant and detoxification defense systems in bees, indicating the presence of oxidative stress. Fungicide exposure elicited a significant depletion in catalase and superoxide dismutase activities and a significant elevation in glutathione and malondialdehyde levels in bees, indicating lipid peroxidation. This is the first study indicating the harmful impacts of tebuconazole + fluopyram on honeybee health.
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