Fate of three insect growth regulators (IGR) insecticides (flufenoxuron, lufenuron and tebufenozide) in grapes following field application and through the wine-making process

Abstract

The dissipation of three insecticide flufenoxuron, lufenuron and tebufenozide residues in grapes after field treatments and during the wine-making process was assessed. Residues were determined in grape, must, centrifuged must and wine samples by HPLC-UV after cyclohexane extraction and clean-up on silica-phase cartridges. Vines in vineyards with white and red grapes located in Central Greece were sprayed once with commercial formulations of each insecticide at the recommended doses in experiments carried out in 2004 and repeated in 2006. The insecticide residues in grapes showed slow reduction for a period of 42 days after application following first-order kinetics with dissipation rates ranged from 0.011 to 0.018 mg kg-1 day-1. However, at the recommended pre-harvest interval (PHI) residues did not exceed 0.27 +/- 0.03 mg kg-1 for flufenoxuron and lufenuron and 0.68 +/- 0.07 mg kg-1 for tebufenozide, and they were clearly lower than the maximum residue limits (MRLs) set by the European Union for grape (2 mg kg-1 for flufenoxuron, 1 mg kg-1 for lufenuron and 3 mg kg-1 for tebufenozide). Grape processing into wine caused an almost complete reduction for flufenoxuron and lufenuron as their residues in wine were below the method LOQs (0.01 mg l-1), but only a moderate reduction for tebufenozide with concentrations from 0.13 to 0.26 mg l-1 measured in the produced wines. Mean transfer factors for tebufenozide of 0.45 for white 'Roditis' and 0.34 for red 'Cabernet Sauvignon' were found from grapes into wine for the wines processed without maceration. The wine-making technique (with or without maceration) had the same influence on tebufenozide residues in wine. Of the various clarifying agents studied, charcoal was found to be the only one effective in removing tebufenozide residues from wine.