پراکنش مکانی- زمانی سوسک برگخوار نارون Xanthogaleruca luteola (Muller) (Coleoptera: Chrysomelidae) در فضای سبز شهر تبریز

Elm trees, Ulmus spp. are widely used in urban green spaces in Iran and the world due to their easy reproduction, adaptability to adverse climatic conditions, and expansive shade. The elm leaf beetle, Xanthogaleruca luteola (Muller) (Coleoptera: Chrysomelidae), is the main pest of elm trees, causing severe damage by feeding on leaves and leading to complete defoliation in high populations. In this study, the spatial and temporal distribution of different life stages of the elm leaf beetle was studied in the green space of Tabriz city, East Azerbaijan Province of Iran. Samplings were conducted weekly from April to September 2023. During sampling, four branches with a length of 40-50 cm were cut from the four main geographical directions of the tree crown, and the different life stages of the leaf beetle were counted and recorded on them. Approximately, 500 grams of the soil at the base of the tree was taken to the laboratory, and prepupae and pupae stages were separated and counted using a sieve with mesh number 16. The spatial locations of the trees were recorded using a hand-held GPS receiver and GS+ 10 software was used for spatial analysis of data obtained from sampling. Variogram components were obtained from structural analysis and degree of dependence values were calculated for all life stages of elm leaf beetle. The results showed that this pest has two generations in Tabriz, and spherical, exponential, and Gaussian variogram models were the best fit for life stages with strong spatial dependence. The high values of the degree of dependence (68-100%) showed that all life stages of the pest had a strong spatial dependence and aggregated distribution, except for the third instar larvae and pupae. Based on these results and our field observations, the elm leaf beetle has a cumulative and patchy distribution; and despite the presence of host trees in most areas of the city, the pest does not have uniform distribution. Therefore, by preparing pest distribution maps, it is possible to locate the hotspots and focus management measures in these areas, and avoid unnecessary spraying in areas where the pest population is low.