Review on imidacloprid diffusion route and a case study: from apple orchard to the honey bee colony matrices

Honey bees play a pivotal role in natural and rural ecosystems by providing human and animal food sources through pollinationservices. However, in cultivated areas, they can be exposed to the chemicals utilized for crop protection. Neonicotinoid insecticidescan adversely affect honey bee colonies impairing their survival, immunity and biological activities at lethal and sublethal doses.For this reason, neonicotinoids, together with other stress factors, like pathogens (e.g. viruses and Varroa mites), climate changeand food shortage, are considered one of the causes of worldwide colony losses. Nevertheless, the natural way of entry and diffusionof these pesticides in field colonies is not completely clear. Here, we wanted to fill this gap by studying the diffusion route ofimidacloprid and its metabolites by analysing different matrices collected from honey bee colonies used for pollination of appleorchards, in the framework of applied Integrated Pest Management strategies. Pollen, honey bees, honey, royal jelly, bee wax andbee bread were sampled from 6 honey bee colonies placed in two different apple orchards before blooming, exposed to chemicalsapplication and removed from the site after that. Samples were analysed using a liquid chromatography-tandem mass spectrometry(UHPLC-MS/MS) and gas chromatography-tandem mass spectrometry (GC-MS/MS) in order to detect imidacloprid, olefin imidacloprid and 5-hydroxy imidacloprid. The results demonstrate that the primary way of entrance of imidacloprid was the pollentransported by foragers, while the main accumulation matrices were bee bread, honey and wax. These findings allow us to hypothesize that the accumulation of this insecticide, especially in bee bread, the main larval food, could potentially impact negatively onhoney bee wellbeing at the adult stage. Moreover, our data could implement the honey bee colony simulator.