Honey bees are constantly exposed to various environmental threats, among which pesticide pollution, including fungicides, is one of the most serious. The bees were 3 days old when they received the experimental solution. This study aimed to evaluate the behavior and mortality of honey bee workers exposed to a commercial formulation of the fungicide tebuconazole (Tebu^® EW, a.i. 25.8%; HELM, Hamburg, Germany). The experiment was conducted under laboratory conditions and lasted 7 days for all experimental groups. The fungicide solution was prepared by adding 6.25 mL of Tebu^® EW per 1 L of water, corresponding to 156.25 mg of tebuconazole (active ingredient) in the prepared solution of sugar syrup. The solution was served in 5 mL dispensers (=group feeding) placed in the cages. This concentration was used for the acute-exposure group (24 h). After 24 h bees were supplied with untreated sugar syrup for the remainder of the experiment. For the chronic-exposure group (168 h), the solution was a 1000-fold dilution of the acute solution, containing 0.15625 mg tebuconazole, dissolved in sugar syrup, provided continuously for 7 days with daily replacement. After 7 days, bee behavior was recorded using a camera and analyzed with Noldus Observer XT software (12.5: Windows 7 64-bit (SP1) version) Five basic honey bee behaviors were examined: walking, flight, self-grooming, contact between individuals and stillness. The results showed statistically significant differences between the experimental groups and the control group (α = 0.05) in the duration of walking, contact between individuals and self-grooming, and the frequency of walking and flight. This was particularly evident for self-grooming; the longer the group was exposed to tebuconazole, the less time the bees spent on this behavior (the acute group spent 47% less time self-grooming and the chronic group spent 88.8% less time self-grooming compared to the control group). Meanwhile, the frequency of walking and flying increased significantly with increasing exposure. No significant differences were observed in the survival between the groups. Based on these findings, it can be concluded that the fungicide containing tebuconazole significantly affects the behavior of honey bee workers.

The effects of fungicides on pollinators remain relatively understudied despite their widespread use and high likelihood of environmental exposure. We assessed the effects of a single exposure to the commercial formulation Tebucur^® 250 EW (containing tebuconazole as the active ingredient) on learning and memory in Bombus terrestris workers. Using the Free-Moving Proboscis Extension Response (FMPER) paradigm, bees were exposed to two concentrations: 9.4 µg of tebuconazole per mL (group T 1/100) and 94 ng of tebuconazole per mL (group T/10,000) of tebuconazole through either pure sucrose (Method 1) or Tebucur^® 250 EW-supplemented sucrose (Method 2) during conditioning. No significant differences between groups were detected during the learning phase (all p > 0.05). In contrast, significant differences emerged during the memory test at the earliest time point (5 min). In Method 1, bees exposed to the higher concentration (treatment group T 1/100) showed significantly lower performance compared to the control group (p < 0.05). In Method 2, the lowest performance was observed in the group exposed to the lower concentration (treatment group T 1/10,000; p < 0.01). No significant differences were detected at later time points (10 and 30 min). These results indicate that a single exposure to Tebucur^® 250 EW (active ingredient: tebuconazole, 250 g/L) can affect short-term memory in bumblebees without impairing initial learning performance. Although the observed effects were subtle and time-limited, they may have important implications for foraging efficiency and pollination under natural conditions.