Behavioral and physiological effects of difenoconazole on stingless bees: A multi-species analysis

Stingless bees, vital to ecosystems and plant production, face increasing threats from pesticide use, with poorly understood potential impacts of fungicides on these pollinators. The goal of this work was to evaluate the effect of contact or oral exposure to difenoconazole, a broad-spectrum fungicide, on foragers of three species of stingless bees: Frieseomelitta varia, Melipona mondury, and Trigona spinipes. The study employed a field-realistic dose of difenoconazole (0.075 mg a.i./mL, referred to as 1×) and its dilutions (10× or 100×) to assess survival and food consumption. The recommended field dose was used to evaluate behaviors, as well as total hemocyte count (THC), and midgut morphology. Contact or oral exposure increased THC in F. varia, while oral exposure decreased food consumed, distance walked, and social interactions, and caused injuries to the midgut. In M. mondury, contact exposure decreased survival and THC while increasing interactions, whereas oral exposure increased walking distance and interactions. For T. spinipes, contact exposure increased walking distance and interactions. Exposures caused adverse effects with variations in the level or type of damage depending on the species and route of exposure. This emphasizes the significance of understanding the potential impacts of fungicides on various pollinators, particularly on stingless bees.