Impact of sulfoxaflor-contaminated beeswax on the population dynamics and mortality of africanized Apis mellifera

Abstract

Currently, herbicides, insecticides, fungicides, and acaricides are the most widely used classes of pesticides worldwide, with insecticides often being associated with the greatest harm to pollinators. Among them, sulfoxaflor (from the sulfoximine chemical group) has been reported to cause significant changes in the gut microbiota of bees, with negative effects on metabolism, development, and defense against pathogens. However, there are few studies investigating beeswax as a potential route of exposure and contamination of the hive by this insecticide. Therefore, this study evaluated the effect of sulfoxaflor, at an environmentally relevant dose, added to beeswax and how it affected colony population development and adult bee mortality. For this purpose, the wax was melted in a water bath (70°C), and sulfoxaflor was added at a concentration of 16.97 µg/kg (environmentally relevant dose). Wax sheets were prepared using a manual sheet and cell mold press and inserted into standard American brood frames. These frames, either with contaminated or uncontaminated wax, were placed in the experimental colonies (5 with sulfoxaflor and 5 control colonies). After the combs were built and the queen began laying eggs, colony population development was monitored weekly over a 60-day period. The brood frames were photographed, and the areas of open and sealed brood were measured (cm²). To assess adult bee mortality, “underbasket” type dead bee collectors were installed below the entrance of the experimental hives, and dead bees were counted daily over the 60-day period. Data were analyzed using ANOVA followed by Student’s t-test (p<0.05). No significant differences were observed between control and treated colonies in open brood area (250.0±272.8 vs. 177.2±170.0 cm²), sealed brood area (346.4±172.8 vs. 306.0±212.8 cm²), or adult bee mortality (6.4±4.3 vs. 6.9±4.3 bees/day). These results suggest that, at the tested concentration, sulfoxaflor did not affect colony population development or adult bee mortality.