Grape Erineum Mite Colomerus vitis (Pgst.) (GEM) is one of the limiting factors of grapevine production in western Iran and it can reduce the level, sugar content and also crop yield. In this survey, effect of GEM on the yield loss investigated in three common grapevine cultivars including Fakhri, Thompson Seedless and Gazne. Also we studied some plant morphological biochemical features potentially related to vine resistance/tolerance. In this order the mentioned cultivars were selected, monitored and sampled in experimental orchards during early April to end of September 2010. Observations showed that Thompson Seedless and Gazne allowed the lowest and highest mite density on the leaves, respectively. As expected, reduction of leaf area, increase of leaf weight, shortening of shoots and erinea formation degree were more relevant on the most infested Gazne, while morphological features of Thompson seedless scarcely suffered by GEM infestation. Statistical analysis showed that diameter of grape berries and their weight had not a significantly difference between infested and control. The studies showed that the mite could decrease the sugar content of the some vine grape cultivars as a Gazne cultivar. In morphological features, the amount of the leaf waxes was highest in White Thompson Seedless on which the lowest mite density, the lowest percentage of erinea and largest healthy leaf areas were detected. Also carbohydrate content of leaves was the lowest on the least mite-infested Thomson seedless and the highest on the most infested Gazne, while phenols decreased in Gazne after mite infestation. Finally, the results of this study indicated that erinea mites have little economic impact on these three vine cultivars.
