The spatial distribution pattern of cereal aphid Sitobion avenae (Hem., Aphididae) in wheat fields of Dehloran

Sitobion avenae (F.) is an important species infesting wheat spikes in region Dehloran, Iran. To evaluate the spatial distribution of O. avenae on wheat, weekly samplings were carried out from five winter wheat fields around Dehloran throughout 2010-2011. Spatial distribution of different developmental stages and morphs of the aphid were described by fitting data to Poisson (random) and negative binomial (clumped) distributions. Based on R2 and F of regression analysis, Taylor’s power law provided a more adequate description of variance/mean relationships than Iwao’s patchiness regression model, and the b values ranged from 1.102 (alate adults) to 1.463 (apterous adults). Other distribution indexes and spatial distribution models showed the cumulative distribution of aphid population on clusters and fitting to negative binominal distribution in many section of season. Mature winged aphids were more likely to show a random distribution compared to other developmental stages.