Residues of captan (contact) and difenoconazole (systemic) fungicides in bee products from an apple orchard

Overview & Synopsis

Ten bee colonies were placed in the middle of a ten-hectare-apple orchard at about 10% in bloom. The orchard was sprayed with a mixture of a contact fungicide, Captan 50WP (active ingredient captan) and a systemic fungicide, Score 250 EC (active ingredient difenoconazole). The residues of fungicides in honey, pollen, and bee bread were then measured by gas chromatography. Honey had very low contamination $- 0.0006$ mg.kg$^{-1}$ of difenoconazole and 0.009 mg.kg$^{-1}$ of captan. Contamination of pollen was much higher - about 0.043 and 2.99 mg.kg$^{-1}$ of difenoconazole and captan, respectively. The most contaminated was bee bread, 0.27 and 6.39 mg.kg$^{-1}$ of difenoconazole and captan, respectively. This finding may be due to some chemical reactions between difenoconazole and some plant metabolites taking place in pollen and bee bread. Difenoconazole, a systemic fungicide, penetrates about 1.66 and 1.16 times more efficiently into honey and bee bread, respectively, than the contact fungicide captan. But in pollen pellets from apple, the penetration coefficient was lower than 1. This observation corroborates the suggestion that in fresh pollen some fungicides may be fixed by sugars, aminoacids, or even proteins.