Effect of covering vine rows on pest and disease incidence, pesticide residue and fresh grape quality
Abstract: Vine rows of table grapes vineyards in Turkey are covered with polypropylene sheets after veraison. This practice allows growers to postpone maturation and harvest period, and to prevent berry cracking due to rainfall as happened in recent years. The effect of covering on population density of insect and mites, incidence of diseases, degradation period of pesticides sprayed and fresh grape quality parameters were investigated in the study. The experiment was conducted in a 2 ha-Sultana Seedless vineyard in Sarıgöl District of Manisa Province in 2012 and 2013. In early August after veraison, rows were covered individually by UV added white colour polypropylene canvas sheets at 2-m-width and 75 cm above the trellising poles. Three rows were left uncovered in the vineyard for comparison. Diseases, insects and mites were checked on 100 bunches visually and 30 leaves under stereo-microscope from early July until harvest weekly. Fresh grapes were sampled from covered and uncovered vines at harvest for quality and residue analysis. The experiment has ended on 1st October 2012 and 23rd October 2013 at harvest. Higher values of relative humidity were recorded in the canopy of covered vines in both years. Most of the pesticide residues were lower than EU and national maximum residue levels in covered and uncovered plots in 2012 and 2013. Covering had no important or statistically significant effect on quality parameters of fresh grape except firmness in berry flesh. Generally, quality parameters were better in uncovered grapes than covered ones. It was proved that covering did not affect the population density of insects and mites and incidence of diseases, and did not cause residue problem by prolonging degradation period of pesticides.