Population Dynamics and Spatial Distribution of Important Thysanoptera Species on Wheat

Population dynamics and spatial distribution of two harmful species of Thysanoptera prevalent on cereal crops (Thrips tabaci Lindman، 1888 and Haplothrips tritici Kurdjomove، 1912)، were investigated during 2009-2011. Weekly sampling was carried out in a one hectar of wheat field in Ramin University of Khuzestan، South-West of Ahvaz. Spatial distribution of immature as well as adults of either species was investigated through Taylor’s power law and Iwao’s patchiness regression methods. The results revealed that the population peak for either species occurs in late March and on the first to middle of April respectively for adults and for larvae. Results of correlation between population dynamics (larval and adult stages) and the factors temperature and precipitation revealed that there is positive vs negative correlations between population fluctuation and the factors of temperature vs humidity. An investigation of the spatial distribution through Taylor’s power law and Iwao’s patchiness regression method indicated that larval stage and total stages in both species are clumped. Based upon R2 and F of regression analysis، Iwaos patchiness provided a more adequate description of spatial distribution than Taylor’s power law for either of the species. Because the seasonal peak in these two species'' density corresponded with the period of peak bloom، thus، in order to study the population dynamics، the earing stage is the most suitable for sampling the thrips on wheat.