Spatial distribution of immature stages of Agonoscena pistaciae (Hemiptera: Aphalaridae) in Rafsanjan region

The common pistachio psyllid, Agonoscena pistaciae Burckhardt & Lauterer (Hemiptera: Aphalaridae), is one of the most important pests of pistachio trees in Iran. To investigate the spatial distribution pattern of egg and nymph of this pest, samplings were done weekly in a pistachio orchards cultivar Kalleh-ghochi. The pistachio terminal leaflet was selected as sampling unit and the number of egg and nymph was recorded in three canopies of tree, up, middle and down parts. The spatial distribution pattern of egg and nymph of A. pistaciae was determined using mean - variance ratio, Taylor´s power low, Iwao´s patchiness regression model and Lloyd's mean crowding index. Based on the mean- variance ratio and Lloyd index, the spatial distribution of egg and nymph, at three canopies of tree was estimated, aggregated. The slope of the regression for Taylor´s power low and Iwao´s patchiness regression model for egg, in middle canopy of tree was significantly more than one, then the spatial distribution was estimated, aggregated and in up and down canopies was estimated, random distribution. In both Taylor´s power low and Iwao´s patchiness regression model, the slope of the regression model for nymph, at three canopies of tree was significantly more than one, then the spatial distribution was estimated aggregated. The results of present study are usefull for developing sampling programs of the common pistachio psyllid.