Bagging Technology Reduces Pesticide Residues in Table Grapes

Most table grape growing regions in China have a continental climate. This climate is conducive for grape diseases. For this reason, our research group developed a bagging technology and a design product twenty years ago to protect the berries from damages by pests. This innovation was granted a patent in 2002 in China. Since then, this patent product has been dramatically extended to grape growers in China. Grape bagging is currently one of the most widely used viticultural practices in the table grape industry in China. However, effects of grape bagging on reduction of pesticide residues were not comprehensively evaluated. In this study, residues of seven pesticides, omethoate, cyhalothrin, mancozeb, methylthiophanate, chlorothalonil, metalaxyl mancozeb and triadimefon, were compared between the bagged and nonbagged berries of the two popular grape cultivars, 'Red Globe' and 'Kyoho', planted in China. The results showed that an annual program of 25 - 30 and 17-20 of pesticide applications were needed in Yangling, a typical region for growing table grapes in China to control diseases in 'Red Globe' and 'Kyoho', respectively. The recovery of the seven pesticides was over 96% and the precision of the determining method (RSD) was around 7% in most cases, indicating that the analytical methods were adequate. Pesticide residues in both of the nonbagged and bagged berries were lower than the grape maximum pesticide residue limits required by China government. The pesticide residues in the bagged berries were reduced to similar to 10 % of the residues in the nonbagged berries. This indicates that the bagging technology extensively reduced the pesticide residues in the berries.