Population fluctuations and spatial distribution of wheat thrips (Haplothrips tritici) in wheat fields of Eyvan city (Ilam Province)

Wheat thrips, Haplothrips tritici (Kurdjumov) (Thysanoptera: Phlaeothripidae) is one of the most important pests in wheat fields in Ilam Province. In order to study the population fluctuations and spatial distribution of wheat thrips in wheat fields of Eyvan city, sampling was weekly carried out during different growing stages of wheat from April to the end of June 2016. Spatial distribution of immature as well as adults of wheat thrips was estimated using Taylor’s power law and Iwao’s patchiness regression methods. The population peaks in both of the irrigated and rainfed wheat fields occurred in middle of May. Based on R2 and F values of regression analysis, in irrigated wheat fields, Iwao's patchiness provided a more adequate description of spatial distribution than Taylor’s power law for wheat thrips. The spatial distribution for adults was randomized but for larval stages and the total stages (larvae and adults) was aggregated. Whereas, in rainfed fields, Taylor’s power law provided a more adequate description of spatial distribution than Iwao's patchiness. The spatial distribution for both larval and adult stages was clumped and for the total was randomized.