Evaluation of oak leaf gall in healthy and declined forest oak (Quercus brantii lindl.) stands of Kohgiluyeh and Boyer-Ahmad province, Iran

Oak trees are hosts of diverse gall-inducing parasites, but the information about the leaf gall is poorly understood. This study aims to examine the weight of leaf galls on oak trees (Quercus brantii Lindl.) in different crown directions with different growth forms (high-forest and coppice) on different geographical slopes in healthy and dry stands of Kohgiluyeh and Boyer-Ahmad province, Iran. For this purpose, two sample plots with a one-ha area involving decline traces of trees (dry) and two sample plots without dieback (control) on the northern and southern slopes in forest sites of Boyer-Ahmad and Dena counties of Iran were selected by field survey. After recording the quantitative variables (DBH, mean diameter of sprout-clump, height and canopy cover), we collected 20 leaves from each direction of the crown of each tree sampled. In the laboratory, the galls were removed from the leaves and weighed. The results showed that there was no statistical significance between the different crown directions of the sample trees in both growth forms, although, in most sites, the northern direction of the trees had more galls. Leaf samples from the south decline site were found to have significantly more gall weight than samples from the other sites in both growth forms. Also, high-forest trees had significantly more leaf galls on their leaves than the coppice trees did. Monthly average temperature and altitude seem to be two determining factors in leaf gall development of the oak trees.