Herbicide residues in grapes and wine

The persistence of several common herbicides from grapes to wine has been s tudied. Shiraz, Tarrango and Doradillo grapes were separately sprayed with either norflurazon, oxyfluorfen, oxadiazon or trifluralin - persistent herb icides commonly used for weed control in vineyards. The dissipation of the herbicides from the grapes was followed for 28 days following treatment. Re sults showed that norflurazon was the most persist herbicide although there were detectable residues of all the herbicides on both red and white grape s at the end of the study period. The penetration of herbicides into the fl esh of the grapes was found to be significantly greater for white grapes th an for red grapes. Small-lot winemaking experiments showed that norflurazon persisted at levels close to the initial concentration through vinificatio n and into the finished wine. The other herbicides degraded, essentially vi a first-order kinetics, within the period of "first fermentation" and had l argely disappeared after 28 days. The use of charcoal together with filter pads, or with diatomaceous earth was shown to be very effective in removing herbicide residues from the wine. A 5% charcoal filter removed more than 9 6% of the norflurazon persisting in the treated wine.