Residues of agrochemicals in beebread as an indicator of landscape management.

The agricultural intensification represents a major threat to biodiversity, with negative effects on the ecosystem. In particular, habitat loss and degradation, along with pesticide use have been recognised as primary factors contributing to the actual global decline of pollinators. Here we investigated the quality of agroecosystems in the Emilia-Romagna region (Northern Italy) within the national monitoring project BeeNet. We analysed pesticide residues in 100 samples of beebread collected in 25 BeeNet stations in March and June 2021 and 2022. We evaluated diversity and concentration of these chemicals, their risk (TWC) to honey bees, and their correlation with land use. Overall, in 84 % of the samples we found 63 out of 373 different pesticide residues, >90 % of them belonging to fungicides and insecticides. The TWC exceeded the risk threshold in seven samples (TWC), mostly due to only one or two compounds. We also found 15 compounds not approved in the EU as plant protection products (PPPs), raising concerns about illegal use or contamination through beeswax recycling. Samples collected in 2021 and in June presented a significantly higher number of active ingredients and TWC than those collected in 2022 and in March. The TWC calculated on single compounds (TWC) exceeded the risk threshold in case of four insecticides, namely carbaryl, fipronil, imidacloprid and thiamethoxam (although each detected in only one sample). Finally, both TWC and number of active ingredients were moderately or highly positively correlated with the percentage of area covered by orchards. Considering that we found on average more than five different molecules per sample, and that we ignored potential synergistic effects, the results of this work highlight the alarming situation regarding pesticide treatments and toxicity risk for bees linked to the current agricultural practices, and the need for implementing sustainable and pollinator-friendly strategies.