Effects of Brining and Picking Time on The Degradation of Pesticide Residue in Grapevine Leaves

Abstract

Intensive pesticide use in vineyard resulted in residue problem on vine leaves that are used as food. This study was aimed at development of a proper chemical control program to reduce the pesticide residue problem on vine (cv. Narince) leaves in vineyards during the growing period. The residues of some fungicides were determined according to spraying time in the fresh (unprocessed) and preserved (brined) leaves. Additionally, the effects of preservation process on degradation of the fungucides residues were investigated. In this study three fungicides (Azoxystrobin, Triadimenol, Hexaconazole) were applied alternately for both powdery mildew and “Colomerus vitis” management, and two fungucides (Copper oxychloride, Metalaxyl + Mancozeb) for downy mildew control. Additionaly vine leaves were harvested at two different times: (i) before the half-life of the pesticides were reached and (ii) after the half-life of the pesticides have elapsed. Two different methods were applied to preserve the vine leaves. In first treatment, leaf samples were boiled in hot (98±2°C) tap water, then leaves were placed into jars, then filled with brine containing 8.0% salt + 0.25% lactic acid. In second treatment, vine leaves were placed into jars, then filled with tap water and brine containing 8.0% salt+0.25% lactic acid. The residue levels of the fungicides were determined on leaves. Detectable copper and the other fungucide residues are compared according to Turkish Food Codex. Preserving applications were decreased fungicide and copper residue levels and hot water brining was decreased the levels of fungicide residues between 75.2% and 99.2%, according to the applications. As a result, systemic fungicides should not be used in vineyards in where pickled vine leaves are produced. It is proposed that better to use contact fungicides instead of systemic one and also viticulturists should be careful using the effective contact fungicides.