Determination of imidacloprid in beehive samples from an open field feeding study

MICHLIG, MELINA; MERKE, JULIETA; BULANCIO CAGNOLO, NATALIA; ORELLANO, EMANUEL; PACINI, ADRIANA; BELDOMÉNICO, HORACIO; REPETTI, MARÍA ROSA

San José

Workshop; 6th Latin American Pesticide Residue Workshop; 2017

Universidad de Costa Rica

Neonicotinoids are characterized by their mode of action that affects the central nervous system of insects and their translocation capabilities. In Argentina imidacloprid is the most used neonicotinoid to protect crops from insects. In previous studies we have found imidacloprid residues in pollen and nectar from sunflower plants representing a risk to pollinators. Therefore an open field feeding study was carried out. For this purpose 30 beehives were displayed in a common field area, and separated in 5 groups (n=6). Each group belonged to a different treatment which was supplied once a week, during 7 weeks, with 500 mL per hive of sucrose solutions containing the following concentrations of imidacloprid: a control and treatments I, II, III and IV with 0, 15, 30, 120 and 240 ng/g, respectively. Throughout the experiment, several parameters were studied, such as population of bees, number of larvae and pollen, nectar and honey storage as well. To check the hives exposure to imidacloprid and evaluate its distribution, sampling of bees and larvae were performed before, during and after of the whole feeding period (7 weeks). Besides, in the 15th week, honey was collected from hive body and honey super of all hives. An analytical methodology based on QuEChERS procedure was optimized and fully validated for bee and honey. After soak of samples and extraction with acetonitrile adding MgSO4 and NaCl salts, a dispersive-SPE step with MgSO4, PSA and C18 was applied. Extracts were evaluated in a UHPLC-MS/MS system. LOQ (ng/g) values were 0.25 in honey and 0.50 in bees, and satisfactory recovery performance was achieved. Results showed scarce differences in colony behaviour through evaluation of whole-hive parameters. Residue concentrations in bees and honey showed correlation with the doses supplied. Conversely, variations in concentrations were not correlated with time during the experience. Significantly larvae did not contained residues of imidacloprid. Sub lethal levels (up to 3 ng/bee) were found in bees samples (LD50).