Mobility and distribution of eight fungicides in surface, skin and pulp in grapes. An application to pyraclostrobin and boscalid

Abstract

The study discusses the mobility and distribution of vinclozolin, dichlofluanid, penconazol, captan, quinoxyfen, fluquinconazol, boscalid and pyraclostrobin residues in surface, skin and pulp in red grapes. A lab test was carried out by immersing grapes in solutions with different concentrations of fungicides and for different periods of time; followed by a determination of the fungicide residues by GC-ECD with an additional confirmation by GC-MS. The distribution between surface, skin and pulp of the grapes was also determined. The percentage sorption ranged from 6.4 to 116%. Results showed that sorption values depended on the time that grapes had been in contact with the fungicide solutions, but not on the initial concentration of solutions. Residues were mainly found in skin, with percentages ranging from 53.0 to 88.4% of total residues. In pulp, these values ranged from 9.6 to 41.7%. Pyraclostrobin showed higher penetration than the other compounds. A field test using three new commercial formulations containing pyraclostrobin, boscalid and a mixture of both, was carried out by applying these formulations to a vineyard. When fungicides were applied individually the ratios of the skin/pulp residues were similar to those obtained in lab; whereas when a mixture of both pesticides was sprayed results showed a lower penetration of the fungicides in the grape pulp.