Monitoring of pesticide residues with beehives in different agroecosystems

The starting point of this work was beekeeper´s and farmer´s concern about the pollution of “Laguna del Cisne”, an important lagoon basin in Uruguay, which is going into a productive reconversion towards pesticides use reduction. Based on previous studies of beehives as biomonitors of pesticide residues, a monitoring was designed and jointly developed. Swarms from the region were captured and hives with new material installed. Five beehives were settled in 8 selected environments: a native forest and agroecosystems involving rice crops, soybean, fruit orchards and horticulture. Five seasonal samplings (January 2019 - May 2020) were performed. The botanical richness of pollen and honey samples was determined (Louveaux et al, 1978). A total of 156 samples of bees (40), wax (40), beebread (36) and honey (40) were analyzed. QuEChERS based multiresidue methodologies followed by GC-MS/MS and LC-MS/MS determinations were employed. From a selection of the most used and toxicologically relevant pesticides, 89, 82, 104 and 103 analytes in bees, wax, beebread and honey respectively were validated according to SANTE/11813/2017 guidelines. LOQs ranged 0.0001-0.100 mg kg-1. From the 44 pesticides and metabolites found 10 were herbicides, 15 fungicides and 19 insecticides. Except 3 samples, concentrations ranged 0.001 - 0.05 mg kg-1. Highest frequencies and number of detections were found in wax and beebread in accordance with our previous monitoring study (2014- 2017). Pesticides profile found in each apiary reflected the land use within its ecosystem. A highlight was the involvement and dialogue between producers and academia in order to advance towards bee protection.